ip classless
What does this command do? thanks in advance **NOTE: New CCNA/CCDA List has been formed. For more information go to http://www.groupstudy.com/list/Associates.html _ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
IP Classless
Hi, Can someone pls. give me a simple explanation of the IP Classless command and why/when it is necessary. Thanks Rashid _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
IP Classless
no ip classless ip route 10.0.0.0 255.0.0.0 10.10.32.0 Whats this mean Thanks _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
ip classless
hi guys, ip classless is for routing protocols to advertise subnets whereas no ip classless is for routing protocols not to advertise subnet info Am I right in saying that? thanks Jason ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
ip classless ?
hi , Anyone knows why when we use RIP or IGRP routing protocols and we have a default network command entered , we need to include ip classless? Any form of input will be greatly appreciated thanks Jason ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: ip classless
When a router looks for a route to a destination, it has two ways of doing it: The classless way, which is the way most of us think, where the packet goes out the most specific (i.e. with the most bits in the network) match. The classful way, where the router first looks at the major network (as defined by its class) and then looks for the right subnet within that network, apparently (according to the answer I'm getting) if it doesn't find the subnet within the net, it drops the packet. That said, the commands "ip classless" and "no ip classless" are used to switch between the modes. I've yet to think a good application for the classful mode :) Francisco. **NOTE: New CCNA/CCDA List has been formed. For more information go to http://www.groupstudy.com/list/Associates.html _ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: ip classless
With this command if a route is not found in the routing table it will take the gateway of last resort if it is set . Without this command it will just drop the packet if a classful route is not found in the routing table. Jason -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Hubert Pun Sent: Friday, September 22, 2000 4:55 AM To: Cisco Study Group Subject: ip classless What does this command do? thanks in advance **NOTE: New CCNA/CCDA List has been formed. For more information go to http://www.groupstudy.com/list/Associates.html _ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] **NOTE: New CCNA/CCDA List has been formed. For more information go to http://www.groupstudy.com/list/Associates.html _ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: IP Classless
With "no ip classless" the router looks for an exact match for a route. If not found the packet is dropped. So if the packet destination is 172.16.33.1 and 172.16.33.0 /24 is not in the table then it goes into the bit bucket. With "ip classless" if an exact match is not found then a less specific route will be chosen. In this case if 172.16.33.0 /24 is not in the table but 172.16.0.0 /16 is in the table then the packet will be routed towards 172.16.0.0. The hope is that at that destination there is a more specific route. Supports route summarization. > -Original Message- > From: Cisco Kid [mailto:[EMAIL PROTECTED]] > Sent: Sunday, October 29, 2000 7:40 AM > To: [EMAIL PROTECTED] > Subject: IP Classless > > > Hi, > > Can someone pls. give me a simple explanation of the IP > Classless command > and why/when it is necessary. > > Thanks > > Rashid > > > _ > FAQ, list archives, and subscription info: > http://www.groupstudy.com/list/cisco.html > Report misconduct > and Nondisclosure violations to [EMAIL PROTECTED] > _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: IP Classless
IP Classless is used for route summarization and for further subnetting a subnet for point-to-point WAN links using VLSM.It is important because by using ip classless u can perform route summarization thereby saving on bandwidth utilization,router processing and reduce the size of routing tables.With regards to VLSM you will be better utilising your IP addressing structure. It also supports discontiguous subnets,thereby letting the subnets communicate with each other. These I think are probably the most common reasons for using ip classless. N.B IP Classful also has something called automatic summarization,but this does not support discontiguous subnets. EIGRP,OSPF,IS-IS,RIPv2,BGP are all classless routing protocols Hope this explains what you want to know >From: "Cisco Kid" <[EMAIL PROTECTED]> >Reply-To: "Cisco Kid" <[EMAIL PROTECTED]> >To: [EMAIL PROTECTED] >Subject: IP Classless >Date: Sun, 29 Oct 2000 13:40:01 - > >Hi, > >Can someone pls. give me a simple explanation of the IP Classless command >and why/when it is necessary. > >Thanks > >Rashid > > >_ >FAQ, list archives, and subscription info: >http://www.groupstudy.com/list/cisco.html >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. Share information about yourself, create your own public profile at http://profiles.msn.com. _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: IP Classless
By default, when performing a look-up in the route table a router will first try to match the major network then the subnet--if there's no match and no default network route, the packet's dropped. Again this is the default behavior. With ip classless, you enable the router to forward the packet to the route with the best match without regard to the class of the destination. Many examples and explanations are available on Cisco's web page and in numerous books on IP routing. Personally I like those in Jeff Doyle's Routing TCP/IP Vol. I Good luck. Aloha, Frank Cisco Kid wrote: > > Hi, > > Can someone pls. give me a simple explanation of the IP Classless command > and why/when it is necessary. > > Thanks > > Rashid _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: IP Classless
let's assume that we have network 10.0.0.0 and its subnet 10.1.0.0/16 10.2.0.0, 10.3.0.0 ... and a default route ip route 0.0.0.0 0.0.0.0 serial 0 10.0.0.0 10.1.0.0 10.2.0.0 10.3.0.0 S 0.0.0.0 0.0.0.0 (Serial 0) when a packet reach the router and ask for the destination 10.1.1.1 (for example) it will match one of the above rule 10.1.0.0. now when another packet reach this router and ask for 10.4.0.1 (for example) now, since there is no rules under the 10.0.0.0 network, it will drop even there is a static route. This is the no IP classless for the ip classless, the packet ask for 10.4.0.1, it doesn;t match the anyrule inside network 10.0.0.0 and DO NOT DROP the packet but seek the best alternative out, in this case is Serial 0 Sam Li - Original Message - From: Cisco Kid <[EMAIL PROTECTED]> Newsgroups: groupstudy.cisco To: <[EMAIL PROTECTED]> Sent: Sunday, October 29, 2000 9:40 PM Subject: IP Classless > Hi, > > Can someone pls. give me a simple explanation of the IP Classless command > and why/when it is necessary. > > Thanks > > Rashid > > > _ > FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: IP Classless
no ip classless means route IP over classful boundaries - you'll have to do your homework to learn the Class A, Class B, and Class C network prefixes though, mate ;-) However, 10.0.0.0 is a private (RFC 1918), non-Internet-routeable Class A network the route statement means that the route to network 10.0.0.0 is through IP address 10.10.32.0 (which is kind of weird, because 10.10.32.0 is network address if the 10.0.0.0 network is masked with 255.0.0.0, but with some other subnet masks it would be a network rather than host address) This is a classful static route, which is consistent with the no ip classless command. -e- - Original Message - From: "John Brandis" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Sunday, April 08, 2001 8:07 PM Subject: IP Classless > no ip classless > ip route 10.0.0.0 255.0.0.0 10.10.32.0 > > Whats this mean > > Thanks _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: IP Classless
At 12:21 AM 4/9/01, EA Louie wrote: >no ip classless means route IP over classful boundaries - you'll have to do >your homework to learn the Class A, Class B, and Class C network prefixes >though, mate ;-) However, 10.0.0.0 is a private (RFC 1918), >non-Internet-routeable Class A network > >the route statement means that the route to network 10.0.0.0 is through IP >address 10.10.32.0 (which is kind of weird, because 10.10.32.0 is network >address if the 10.0.0.0 network is masked with 255.0.0.0, but with some Isn't it node 10.32.0 on network 10? Though I agree it's weird. We need to see more of the router's config and more info on the topology and addressing scheme. They seem to be using variable-lenght subnet masking. Priscilla >other subnet masks it would be a network rather than host address) This is >a classful static route, which is consistent with the no ip classless >command. > >-e- > >- Original Message - >From: "John Brandis" <[EMAIL PROTECTED]> >To: <[EMAIL PROTECTED]> >Sent: Sunday, April 08, 2001 8:07 PM >Subject: IP Classless > > > > no ip classless > > ip route 10.0.0.0 255.0.0.0 10.10.32.0 > > > > Whats this mean > > > > Thanks Priscilla Oppenheimer http://www.priscilla.com _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: ip classless
Wrong. ip classless allows a router receiving a packet it doesn't know how to forward (unrecognized subnet and no default route in the routing table) to choose the best supernet to forward it finally. Otherwise with no ip classless, the packet is discarded. cvp ccnp, ccda "Yee, Jason" <[EMAIL PROTECTED]> on 08/22/2000 05:22:30 PM Please respond to "Yee, Jason" <[EMAIL PROTECTED]> To: "'[EMAIL PROTECTED]'" <[EMAIL PROTECTED]> cc: (bcc: Claude-Vincent PEREZ/JP-TOKYO-HOLDING/LVMH) Subject: ip classless hi guys, ip classless is for routing protocols to advertise subnets whereas no ip classless is for routing protocols not to advertise subnet info Am I right in saying that? thanks Jason ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: ip classless ?
Ah yes, classful addressing. Blast from the past... I am assuming you are aware of the classes of IP addresses, and how a class A address has a first octet of 1-127, etc.. Well, what IP Classless means is that the router *does not* assume that an IP address with a first octet of 1-126 is a /8 address, 128-191 a /16 address, 192-223 a /24 address and so forth. Sound a bit archaic? Hmm... So are IGRP and RIP. ; ) Your question is kind of tough to answer directly, since you do not need to use IP Classless unless you need to break, say a 10.x.x.x network into /24 subnets. If you don't include IP Classless, the router will assume the mask is instead /8 and things will get weird... HTH, Casey >From: "Yee, Jason" <[EMAIL PROTECTED]> >Reply-To: "Yee, Jason" <[EMAIL PROTECTED]> >To: "'[EMAIL PROTECTED]'" <[EMAIL PROTECTED]> >Subject: ip classless ? >Date: Tue, 22 Aug 2000 22:07:51 -0500 > >hi , > >Anyone knows why when we use RIP or IGRP routing protocols and we have a >default network command entered , we need to include ip classless? > >Any form of input will be greatly appreciated > > >thanks > > >Jason > >___ >UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html >FAQ, list archives, and subscription info: http://www.groupstudy.com >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: ip classless ?
Turns out that ip classless is enabled by default. Perhaps that is why you need to use "no ip classless" See the www.cisco.com for details. Ip Classless - 11.3 The default behavior changed from disabled to enabled -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Yee, Jason Sent: Tuesday, August 22, 2000 8:08 PM To: '[EMAIL PROTECTED]' Subject: ip classless ? hi , Anyone knows why when we use RIP or IGRP routing protocols and we have a default network command entered , we need to include ip classless? Any form of input will be greatly appreciated thanks Jason ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: ip classless ?
RIP and IGRP are Classful routing protocols. Meaning that they will recognize and IP by the first octet and automatically use the default mask associated with that class. They will disregard any subnets. Therefore you have the ip classless command which tells these protocols to forget about the default mask and listen to subnet information. Make Sense? Adam Hickey [EMAIL PROTECTED] - Original Message - From: "Yee, Jason" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Tuesday, August 22, 2000 8:07 PM Subject: ip classless ? > hi , > > Anyone knows why when we use RIP or IGRP routing protocols and we have a > default network command entered , we need to include ip classless? > > Any form of input will be greatly appreciated > > > thanks > > > Jason > > ___ > UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html > FAQ, list archives, and subscription info: http://www.groupstudy.com > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: ip classless ?
This is wrong amigo. The 'ip classless' command is used when configuring default routes. It is used because when you create a default route on a router it gets advertised as 0.0.0.0 in addition to the default network. When a router recieves the advertised default route it will forward packets to a destination which does not appear in its routing table. Specifically you need to use the 'ip classless' command when using IGRP and EIGRP because they only advertise the network you configured on them. If you do not use this command to enable the default path to be used for non-connected subnets of the same major classful network, the packets will be dropped at the router. - Original Message - From: Casey Fahey <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]> Sent: Tuesday, August 22, 2000 8:48 PM Subject: Re: ip classless ? > Ah yes, classful addressing. Blast from the past... > > I am assuming you are aware of the classes of IP addresses, and how a > class A address has a first octet of 1-127, etc.. > > Well, what IP Classless means is that the router *does not* assume that an > IP address with a first octet of 1-126 is a /8 address, 128-191 a /16 > address, 192-223 a /24 address and so forth. > > Sound a bit archaic? Hmm... So are IGRP and RIP. ; ) > > Your question is kind of tough to answer directly, since you do not need to > use IP Classless unless you need to break, say a 10.x.x.x network into /24 > subnets. If you don't include IP Classless, the router will assume the mask > is instead /8 and things will get weird... > > HTH, > > Casey > > >From: "Yee, Jason" <[EMAIL PROTECTED]> > >Reply-To: "Yee, Jason" <[EMAIL PROTECTED]> > >To: "'[EMAIL PROTECTED]'" <[EMAIL PROTECTED]> > >Subject: ip classless ? > >Date: Tue, 22 Aug 2000 22:07:51 -0500 > > > >hi , > > > >Anyone knows why when we use RIP or IGRP routing protocols and we have a > >default network command entered , we need to include ip classless? > > > >Any form of input will be greatly appreciated > > > > > >thanks > > > > > >Jason > > > >___ > >UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html > >FAQ, list archives, and subscription info: http://www.groupstudy.com > >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > > Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com > > ___ > UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html > FAQ, list archives, and subscription info: http://www.groupstudy.com > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: ip classless ?
Hmmm, let's see where to start 1: EIGRP uses classless routing by default unlike IGRP. 2: Default routes refer to static routes--not dynamic routes used in RIP, EIGRP, IGRP, etc. 3: The command "ip route 0.0.0.0 0.0.0.0 w.x.y.z" enables a default route--not "ip classless" By the way, this is thepuffer's friend ( not the puffer ) responding to this. I just couldn't resist. Also, I hope I didn't make any major mistakes in my claims. If so I will be really bummed. - Original Message - From: "whatshakin" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Wednesday, August 23, 2000 12:27 AM Subject: Re: ip classless ? > This is wrong amigo. > > The 'ip classless' command is used when configuring default routes. It is > used because when you create a default route on a router it gets advertised > as 0.0.0.0 in addition to the default network. When a router recieves the > advertised default route it will forward packets to a destination which does > not appear in its routing table. Specifically you need to use the 'ip > classless' command when using IGRP and EIGRP because they only advertise the > network you configured on them. If you do not use this command to enable > the default path to be used for non-connected subnets of the same major > classful network, the packets will be dropped at the router. > > > - Original Message - > From: Casey Fahey <[EMAIL PROTECTED]> > To: <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]> > Sent: Tuesday, August 22, 2000 8:48 PM > Subject: Re: ip classless ? > > > > Ah yes, classful addressing. Blast from the past... > > > > I am assuming you are aware of the classes of IP addresses, and how a > > class A address has a first octet of 1-127, etc.. > > > > Well, what IP Classless means is that the router *does not* assume that an > > IP address with a first octet of 1-126 is a /8 address, 128-191 a /16 > > address, 192-223 a /24 address and so forth. > > > > Sound a bit archaic? Hmm... So are IGRP and RIP. ; ) > > > > Your question is kind of tough to answer directly, since you do not need > to > > use IP Classless unless you need to break, say a 10.x.x.x network into /24 > > subnets. If you don't include IP Classless, the router will assume the > mask > > is instead /8 and things will get weird... > > > > HTH, > > > > Casey > > > > >From: "Yee, Jason" <[EMAIL PROTECTED]> > > >Reply-To: "Yee, Jason" <[EMAIL PROTECTED]> > > >To: "'[EMAIL PROTECTED]'" <[EMAIL PROTECTED]> > > >Subject: ip classless ? > > >Date: Tue, 22 Aug 2000 22:07:51 -0500 > > > > > >hi , > > > > > >Anyone knows why when we use RIP or IGRP routing protocols and we have a > > >default network command entered , we need to include ip classless? > > > > > >Any form of input will be greatly appreciated > > > > > > > > >thanks > > > > > > > > >Jason > > > > > >___ > > >UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html > > >FAQ, list archives, and subscription info: http://www.groupstudy.com > > >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > > > > > Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com > > > > ___ > > UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html > > FAQ, list archives, and subscription info: http://www.groupstudy.com > > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > > > ___ > UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html > FAQ, list archives, and subscription info: http://www.groupstudy.com > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: ip classless ?
Casey is right. I've setup quite a few Internet connections where no routing protocols are used and in order to route correctly when using a supernetted class A or other, you must use ip classless or you ain't goin' nowhere. Dave -Original Message- From: whatshakin [mailto:[EMAIL PROTECTED]] Sent: Wednesday, August 23, 2000 3:27 AM To: [EMAIL PROTECTED] Subject: Re: ip classless ? This is wrong amigo. The 'ip classless' command is used when configuring default routes. It is used because when you create a default route on a router it gets advertised as 0.0.0.0 in addition to the default network. When a router recieves the advertised default route it will forward packets to a destination which does not appear in its routing table. Specifically you need to use the 'ip classless' command when using IGRP and EIGRP because they only advertise the network you configured on them. If you do not use this command to enable the default path to be used for non-connected subnets of the same major classful network, the packets will be dropped at the router. - Original Message - From: Casey Fahey <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]> Sent: Tuesday, August 22, 2000 8:48 PM Subject: Re: ip classless ? > Ah yes, classful addressing. Blast from the past... > > I am assuming you are aware of the classes of IP addresses, and how a > class A address has a first octet of 1-127, etc.. > > Well, what IP Classless means is that the router *does not* assume that an > IP address with a first octet of 1-126 is a /8 address, 128-191 a /16 > address, 192-223 a /24 address and so forth. > > Sound a bit archaic? Hmm... So are IGRP and RIP. ; ) > > Your question is kind of tough to answer directly, since you do not need to > use IP Classless unless you need to break, say a 10.x.x.x network into /24 > subnets. If you don't include IP Classless, the router will assume the mask > is instead /8 and things will get weird... > > HTH, > > Casey > > >From: "Yee, Jason" <[EMAIL PROTECTED]> > >Reply-To: "Yee, Jason" <[EMAIL PROTECTED]> > >To: "'[EMAIL PROTECTED]'" <[EMAIL PROTECTED]> > >Subject: ip classless ? > >Date: Tue, 22 Aug 2000 22:07:51 -0500 > > > >hi , > > > >Anyone knows why when we use RIP or IGRP routing protocols and we have a > >default network command entered , we need to include ip classless? > > > >Any form of input will be greatly appreciated > > > > > >thanks > > > > > >Jason > > > >___ > >UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html > >FAQ, list archives, and subscription info: http://www.groupstudy.com > >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > > Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com > > ___ > UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html > FAQ, list archives, and subscription info: http://www.groupstudy.com > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: ip classless ?
Puffers Buddy, Actually you are correct about configuring a default route, BUT you won't be able to use that default static route if you don't enable your router with IP classless (enabled by default in 11.2 and up). IP classless allows a router to use the best "supernetted" route. Whatshakin wrote: Specifically you need to use the 'ip > classless' command when using IGRP and EIGRP because they only advertise the * network you configured on them. The above statement is not true. The network statement under the routing process (whether IGRP or EIGRP) only identifies the interfaces that will participate in routing updates. It does not only route those networks. You can redistribute static route's (i.e default 0.0.0.0 routes) into your routing protocols and that route will get propagated out to other routers running that routing protocol and AS over the interfaces configured with and IP address in the network statement under the routing process. David -Original Message- From: Adam Hickey [mailto:[EMAIL PROTECTED]] Sent: Wednesday, August 23, 2000 4:26 PM To: [EMAIL PROTECTED] Subject:Re: ip classless ? Hmmm, let's see where to start 1: EIGRP uses classless routing by default unlike IGRP. 2: Default routes refer to static routes--not dynamic routes used in RIP, EIGRP, IGRP, etc. 3: The command "ip route 0.0.0.0 0.0.0.0 w.x.y.z" enables a default route--not "ip classless" By the way, this is thepuffer's friend ( not the puffer ) responding to this. I just couldn't resist. Also, I hope I didn't make any major mistakes in my claims. If so I will be really bummed. - Original Message - From: "whatshakin" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Wednesday, August 23, 2000 12:27 AM Subject: Re: ip classless ? > This is wrong amigo. > > The 'ip classless' command is used when configuring default routes. It is > used because when you create a default route on a router it gets advertised > as 0.0.0.0 in addition to the default network. When a router recieves the > advertised default route it will forward packets to a destination which does > not appear in its routing table. Specifically you need to use the 'ip > classless' command when using IGRP and EIGRP because they only advertise the > network you configured on them. If you do not use this command to enable > the default path to be used for non-connected subnets of the same major > classful network, the packets will be dropped at the router. > > > - Original Message - > From: Casey Fahey <[EMAIL PROTECTED]> > To: <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]> > Sent: Tuesday, August 22, 2000 8:48 PM > Subject: Re: ip classless ? > > > > Ah yes, classful addressing. Blast from the past... > > > > I am assuming you are aware of the classes of IP addresses, and how a > > class A address has a first octet of 1-127, etc.. > > > > Well, what IP Classless means is that the router *does not* assume that an > > IP address with a first octet of 1-126 is a /8 address, 128-191 a /16 > > address, 192-223 a /24 address and so forth. > > > > Sound a bit archaic? Hmm... So are IGRP and RIP. ; ) > > > > Your question is kind of tough to answer directly, since you do not need > to > > use IP Classless unless you need to break, say a 10.x.x.x network into /24 > > subnets. If you don't include IP Classless, the router will assume the > mask > > is instead /8 and things will get weird... > > > > HTH, > > > > Casey > > > > >From: "Yee, Jason" <[EMAIL PROTECTED]> > > >Reply-To: "Yee, Jason" <[EMAIL PROTECTED]> > > >To: "'[EMAIL PROTECTED]'" <[EMAIL PROTECTED]> > > >Subject: ip classless ? > > >Date: Tue, 22 Aug 2000 22:07:51 -0500 > > > > > >hi , > > > > > >Anyone knows why when we use RIP or IGRP routing protocols and we have a > > >default network command entered , we need to include ip classless? > > > > > >Any form of input will be greatly appreciated > > > > > > > > >thanks > > > > > > > > >Jason > > > > > >___ > > >UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html > > >FAQ, list archives, and subscription info: http://www.groupstudy.com > > >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > > > > > Get Your Private, Free E-mail from MSN Hotmail at ht
Re: ip classless ?
Wrong? Me? Golly, I had trouble sleeping last night after reading that...! ; ) Your definition is almost word-for-word what is reflected in the CCO docs or a textbook. The docs say what the entry does, but say little about how or why, which was the essence of the original question. So, I wanted to frame the overall concept in a way that is more easily understood. I take for granted that most folks have gone to CCO to look at the definition there, and did not feel it was neccesary to copy and paste that. What we REALLY wanted to do is look under the hood and achieve an understanding as to WHY, and how it might impact our network design decisions. (Like, don't use RIP or IGRP...? :) ) Just for grins, the definition I prefer, from Jeff Doyle's book, pp765 "IP Classless : Enables classless route lookups so that the router can forward packets to unknown subnets of directly connected networks." Beyond this, I agree that your statment is correct, but somewhat incomplete and therefore misleading. The meat of the issue IMO is the paradigm shift between Classful and Classless address space, routing and the ramifications when it comes to early distance-vector routing protocols. Have a good one, Casey >From: "whatshakin" <[EMAIL PROTECTED]> >Reply-To: "whatshakin" <[EMAIL PROTECTED]> >To: <[EMAIL PROTECTED]> >Subject: Re: ip classless ? >Date: Wed, 23 Aug 2000 00:27:27 -0700 > >This is wrong amigo. > >The 'ip classless' command is used when configuring default routes. It is >used because when you create a default route on a router it gets advertised >as 0.0.0.0 in addition to the default network. When a router recieves the >advertised default route it will forward packets to a destination which >does >not appear in its routing table. Specifically you need to use the 'ip >classless' command when using IGRP and EIGRP because they only advertise >the >network you configured on them. If you do not use this command to enable >the default path to be used for non-connected subnets of the same major >classful network, the packets will be dropped at the router. > > >- Original Message ----- >From: Casey Fahey <[EMAIL PROTECTED]> >To: <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]> >Sent: Tuesday, August 22, 2000 8:48 PM >Subject: Re: ip classless ? > > > > Ah yes, classful addressing. Blast from the past... > > > > I am assuming you are aware of the classes of IP addresses, and how a > > class A address has a first octet of 1-127, etc.. > > > > Well, what IP Classless means is that the router *does not* assume that >an > > IP address with a first octet of 1-126 is a /8 address, 128-191 a /16 > > address, 192-223 a /24 address and so forth. > > > > Sound a bit archaic? Hmm... So are IGRP and RIP. ; ) > > > > Your question is kind of tough to answer directly, since you do not need >to > > use IP Classless unless you need to break, say a 10.x.x.x network into >/24 > > subnets. If you don't include IP Classless, the router will assume the >mask > > is instead /8 and things will get weird... > > > > HTH, > > > > Casey > > > > >From: "Yee, Jason" <[EMAIL PROTECTED]> > > >Reply-To: "Yee, Jason" <[EMAIL PROTECTED]> > > >To: "'[EMAIL PROTECTED]'" <[EMAIL PROTECTED]> > > >Subject: ip classless ? > > >Date: Tue, 22 Aug 2000 22:07:51 -0500 > > > > > >hi , > > > > > >Anyone knows why when we use RIP or IGRP routing protocols and we have >a > > >default network command entered , we need to include ip classless? > > > > > >Any form of input will be greatly appreciated > > > > > > > > >thanks > > > > > > > > >Jason > > > > > >___ > > >UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html > > >FAQ, list archives, and subscription info: http://www.groupstudy.com > > >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > > > > > Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com > > > > ___ > > UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html > > FAQ, list archives, and subscription info: http://www.groupstudy.com > > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > > >___ >UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html >FAQ, list archives, and subscription info: http://www.groupstudy.com >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: ip classless ?
Guy's, "When classless routing is in effect, if a router receives packets destined for a subnet of a network that has no network default route, the router forwards the packet to the best supernet route." Fenris
Re: ip classless ?
My apologies, that was a little harsh, I thought your answer was a little too vague. In hindsight it certainly wasn't wrong. I like that Doyle description you cited, it is quite succinct. You are also right in that my post was a little misleading, I should have gone to bed instead of trying to think at that time of the morning. Hope you get some ZZZ's tonight! - Original Message - From: Casey Fahey <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Wednesday, August 23, 2000 8:36 AM Subject: Re: ip classless ? > Wrong? Me? Golly, I had trouble sleeping last night after reading that...! > ; ) > > Your definition is almost word-for-word what is reflected in the CCO docs or > a textbook. The docs say what the entry does, but say little about how or > why, which was the essence of the original question. So, I wanted to frame > the overall concept in a way that is more easily understood. > > I take for granted that most folks have gone to CCO to look at the > definition there, and did not feel it was neccesary to copy and paste that. > What we REALLY wanted to do is look under the hood and achieve an > understanding as to WHY, and how it might impact our network design > decisions. (Like, don't use RIP or IGRP...? :) ) > > Just for grins, the definition I prefer, from Jeff Doyle's book, pp765 "IP > Classless : Enables classless route lookups so that the router can forward > packets to unknown subnets of directly connected networks." > > Beyond this, I agree that your statment is correct, but somewhat incomplete > and therefore misleading. The meat of the issue IMO is the paradigm shift > between Classful and Classless address space, routing and the ramifications > when it comes to early distance-vector routing protocols. > > Have a good one, > > Casey > > >From: "whatshakin" <[EMAIL PROTECTED]> > >Reply-To: "whatshakin" <[EMAIL PROTECTED]> > >To: <[EMAIL PROTECTED]> > >Subject: Re: ip classless ? > >Date: Wed, 23 Aug 2000 00:27:27 -0700 > > > >This is wrong amigo. > > > >The 'ip classless' command is used when configuring default routes. It is > >used because when you create a default route on a router it gets advertised > >as 0.0.0.0 in addition to the default network. When a router recieves the > >advertised default route it will forward packets to a destination which > >does > >not appear in its routing table. Specifically you need to use the 'ip > >classless' command when using IGRP and EIGRP because they only advertise > >the > >network you configured on them. If you do not use this command to enable > >the default path to be used for non-connected subnets of the same major > >classful network, the packets will be dropped at the router. > > > > > >- Original Message - > >From: Casey Fahey <[EMAIL PROTECTED]> > >To: <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]> > >Sent: Tuesday, August 22, 2000 8:48 PM > >Subject: Re: ip classless ? > > > > > > > Ah yes, classful addressing. Blast from the past... > > > > > > I am assuming you are aware of the classes of IP addresses, and how a > > > class A address has a first octet of 1-127, etc.. > > > > > > Well, what IP Classless means is that the router *does not* assume that > >an > > > IP address with a first octet of 1-126 is a /8 address, 128-191 a /16 > > > address, 192-223 a /24 address and so forth. > > > > > > Sound a bit archaic? Hmm... So are IGRP and RIP. ; ) > > > > > > Your question is kind of tough to answer directly, since you do not need > >to > > > use IP Classless unless you need to break, say a 10.x.x.x network into > >/24 > > > subnets. If you don't include IP Classless, the router will assume the > >mask > > > is instead /8 and things will get weird... > > > > > > HTH, > > > > > > Casey > > > > > > >From: "Yee, Jason" <[EMAIL PROTECTED]> > > > >Reply-To: "Yee, Jason" <[EMAIL PROTECTED]> > > > >To: "'[EMAIL PROTECTED]'" <[EMAIL PROTECTED]> > > > >Subject: ip classless ? > > > >Date: Tue, 22 Aug 2000 22:07:51 -0500 > > > > > > > >hi , > > > > > > > >Anyone knows why when we use RIP or IGRP routing protocols and we have > >a > > > >default network command entered , we need to include ip classless? > > > > > > > >Any form of input will be
Re: ip classless ?
The ip classless command is used when setting up default routes. Cisco routers (classful by default) expect a subnet mask when entering your static ip route commands, so when you are setting up a default route, you must specify ip classless, since no remote subnets will be in its routing table for default routes. Matt ""Yee, Jason"" <[EMAIL PROTECTED]> wrote in message 859B90209E2FD311BE5600902751445D2E7CF4@LYNX">news:859B90209E2FD311BE5600902751445D2E7CF4@LYNX... > hi , > > Anyone knows why when we use RIP or IGRP routing protocols and we have a > default network command entered , we need to include ip classless? > > Any form of input will be greatly appreciated > > > thanks > > > Jason > > ___ > UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html > FAQ, list archives, and subscription info: http://www.groupstudy.com > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > --- ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: ip classless ?
yes "Yee, Jason" <[EMAIL PROTECTED]> wrote in message 859B90209E2FD311BE5600902751445D2E7CF4@LYNX">news:859B90209E2FD311BE5600902751445D2E7CF4@LYNX... > hi , > > Anyone knows why when we use RIP or IGRP routing protocols and we have a > default network command entered , we need to include ip classless? > > Any form of input will be greatly appreciated > > > thanks > > > Jason > > ___ > UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html > FAQ, list archives, and subscription info: http://www.groupstudy.com > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > --- ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: ip classless ?
-Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of Matt Gravlin Sent: Saturday, August 26, 2000 9:49 PM To: [EMAIL PROTECTED] Subject:Re: ip classless ? The ip classless command is used when setting up default routes. Cisco routers (classful by default) expect a subnet mask when entering your static ip route commands, so when you are setting up a default route, you must specify ip classless, since no remote subnets will be in its routing table for default routes. -- CL: this is not exactly correct. I took the following from the documentation home page, configuration guides. In this case 12.1, but it applied to earlier IOS versions as well. Classfull versus classless behavior of Cisco routers remains a bit confusing, and therefore highly misunderstood topic. The IP Classless command ( or classless behavior ) is on by default in the newer IOS, anyway, as noted below. It operates in case default routes do not exist. If there are default routes, then the behavior may or may not be necessary, depending upon other factors. http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121cgcr/ip_c /ipcprt1/1cdipadr.htm#1001090 watch this nasty word wrap By default, classless routing behavior is enabled on the router. When classless routing is in effect, if a router receives packets destined for a subnet of a network that has no network default route, the router forwards the packet to the best supernet route. In Figure 1, classless routing is enabled in the router. Therefore, when the host sends a packet to 128.20.4.1, instead of discarding the packet, the router forwards the packet to the best supernet route. If you disable classless routing, and a router receives packets destined for a subnet of a network that has no network default route, the router discards the packet. Figure 2 shows a router in network 128.20.0.0 connected to subnets 128.20.1.0, 128.20.2.0, and 128.20.3.0. Suppose the host sends a packet to 128.20.4.1. Because there is no network default route, the router discards the packet. To prevent the Cisco IOS software from forwarding packets destined for unrecognized subnets to the best supernet route possible, use the following command in global configuration mode: no ip classless Disable classless routing behavior. === Matt ""Yee, Jason"" <[EMAIL PROTECTED]> wrote in message 859B90209E2FD311BE5600902751445D2E7CF4@LYNX">news:859B90209E2FD311BE5600902751445D2E7CF4@LYNX... > hi , > > Anyone knows why when we use RIP or IGRP routing protocols and we have a > default network command entered , we need to include ip classless? > > Any form of input will be greatly appreciated > > > thanks > > > Jason > > ___ > UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html > FAQ, list archives, and subscription info: http://www.groupstudy.com > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > --- ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: ip classless ?
Let me explain the difference. The best description of it I've seen documented is in the networkers 2000 or 1999 Intro to routing presentation I believe. I can't locate it at the moment. Anyway, the 'ip classless' and 'no ip classless' global IP options modify the routers *forwarding* decision. It is independent of routing protocols and doesn't effect the way routing protocols work. In the Bay world, this option is known as Default-Route-For-Subnets-Enable in SM or classless in BCC. It really doesn't have anything to do with default routes however. With 'ip classless' on the router follows the longest-match method. With classful forwarding (no ip classless) if you have a default route pointing to a 172.16.10.1 address for example and you have a directly connected network of 172.16.20.x and 172.16.30.x all these are class B networks to the router (172.16.0.0) because were doing classful forwarding. Your routing table will look like below: 172.16.0.0 172.16.20.x directly connected 172.16.30.x directly connected 0.0.0.0 . 172.16.30.1 (somewhere else) So, we do a ping to 172.16.10.1 which is a network somewhere else, what happens is the router forwards this as 172.16.0.0 and tries to send it out its directly connected interfaces and theres no 172.16.10.x directly connected, so it will fail and drop the packet without even trying the default route or other routes in the routing table. Turn on 'ip classless' and it will take the other routes... see the archives for a more detailed discussion. __ Do You Yahoo!? Yahoo! Mail - Free email you can access from anywhere! http://mail.yahoo.com/ ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
IP classless/Default routes
In Todd Lammle's book for CCNA 640-407, on p. 202 he has set a default route of BOTH 172.16.40.2 and 172.16.20.1. How does one do this, just enter the IP route command as such, one right after the other (??): ip route 0.0.0.0 0.0.0.0 162.16.40.2 ip route 0.0.0.0 0.0.0.0 162.16.20.1 ??? The reason I ask is that in his book for CCNA 640-507, he states on page 253, "Default routing is used to send packets with a remote destination network not in the routing table to the next hop router. You can only use default routing on stub networks, which means that they have only one exit port out of the network." The two books seem to say contradictory things. Is it because the 507 exam is based on a different IOS? What gives? Dave Page ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
IP classless/Default routes
and points. Hope this helps clear up your question, forget what the book said this is how a real router works. Not that I'm knocking Todd's book, I love his work, but there is a lot to say about trying it out. Thanks Duck - Original Message - From: Donald B Johnson Jr <[EMAIL PROTECTED]> To: Dave Page <[EMAIL PROTECTED]>; 'Cisco List' <[EMAIL PROTECTED]> Sent: Tuesday, August 08, 2000 11:14 AM Subject: Re: IP classless/Default routes > I believe that is a mistake in Todd's book. You can only have one default > gateway set. > Otherwise the packet would not know where to send the packet. > Duck > - Original Message - > From: Dave Page <[EMAIL PROTECTED]> > To: 'Cisco List' <[EMAIL PROTECTED]> > Sent: Monday, August 07, 2000 5:05 PM > Subject: IP classless/Default routes > > > > > > In Todd Lammle's book for CCNA 640-407, on p. 202 he has set a default > route > > of BOTH 172.16.40.2 and 172.16.20.1. How does one do this, just enter the > > IP route command as such, one right after the other (??): > > > > ip route 0.0.0.0 0.0.0.0 162.16.40.2 > > ip route 0.0.0.0 0.0.0.0 162.16.20.1 > > > > ??? > > > > > > The reason I ask is that in his book for CCNA 640-507, he states on page > > 253, "Default routing is used to send packets with a remote destination > > network not in the routing table to the next hop router. You can only use > > default routing on stub networks, which means that they have only one exit > > port out of the network." > > > > The two books seem to say contradictory things. Is it because the 507 > exam > > is based on a different IOS? What gives? > > > > > > Dave Page > > > > ___ > > UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html > > FAQ, list archives, and subscription info: http://www.groupstudy.com > > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > ___ > UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html > FAQ, list archives, and subscription info: http://www.groupstudy.com ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
IP classless/Default routes
Actually, I believe this is incorrect. If you enter two static default routes with the same administrative distance (in this case 1) then (depending on any configured maximum paths statement, I believe the default is 4) the router will load balance using both addresses. If the router will load balance on per-packet or per-destination basis will depend on the switching method used. The reason one of your default routes dissapear when you disconnect one of your ethernet segments is that the route to your next hop address for that default route dissapears. If a router does not have a route to the next hop address then it will not install that route into the route table even though it is statically configured. To test this scenario using your previous example try adding a static route to 10.1.1.0 255.255.255.0 with a next hop address of 10.1.2.3. When both ethernet interfaces are up you won't see that new static route for 10.1.1.3 in the table because the administrative distance for that route is 1. The router as a connected route with an administrative distance of 0 out it's ethernet interface for that network. As soon as you remove the cable from the ethernet interface with 10.1.1.1 connected to it (e0/0) the static route for 10.1.1.0 255.255.255.0 with next hop 10.1.2.3 will show up. At the same time both default statics will remain in the routing table and be used in a load sharing state. Michael Cohen CCDP, CCNP CCIE #6080 -Original Message- From: Donald B Johnson Jr [mailto:[EMAIL PROTECTED]] Sent: Tuesday, August 08, 2000 3:02 PM To: [EMAIL PROTECTED]; Dave Page Subject: IP classless/Default routes Dave Let me clear this up a little, you can place more than one default route in the routing table but the router will only use the first entry. If that link goes down the next default route will be used. Here is the config, interface Ethernet0/0 ip address 10.1.1.1 255.255.255.0 no ip directed-broadcast interface Ethernet0/1 ip address 10.1.2.1 255.255.255.0 no ip directed-broadcast Router#conf Configuring from terminal, memory, or network [terminal]? Enter configuration commands, one per line. End with CNTL/Z. Router(config)#ip routing Router(config)#ip route 0.0.0.0 0.0.0.0 10.1.1.3 Router(config)#ip route 0.0.0.0 0.0.0.0 10.1.2.3 Router(config)#^Z Router# 00:08:49: %SYS-5-CONFIG_I: Configured from console by console Router#sh ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default U - per-user static route, o - ODR Gateway of last resort is 10.1.1.3 to network 0.0.0.0 10.0.0.0/24 is subnetted, 2 subnets C 10.1.2.0 is directly connected, Ethernet0/1 C 10.1.1.0 is directly connected, Ethernet0/0 S* 0.0.0.0/0 [1/0] via 10.1.1.3 [1/0] via 10.1.2.3 Router# Notice that the first ip route entry is the Gateway of last resort. Now watch what happens when I disconnect the cable to E0/0 Router# 00:15:20: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0/0, changed s tate to down Router#sh ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default U - per-user static route, o - ODR Gateway of last resort is 10.1.2.3 to network 0.0.0.0 10.0.0.0/24 is subnetted, 1 subnets C 10.1.2.0 is directly connected, Ethernet0/1 S* 0.0.0.0/0 [1/0] via 10.1.2.3 Router# Now notice that the second ip route entry is the Gateway of last resort. Now watch what happens when I reconnect the E0/0 cable. Router# 00:19:27: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0/0, changed s tate to up Router#sh ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default U - per-user static route, o - ODR Gateway of last resort is 10.1.2.3 to network 0.0.0.0 10.0.0.0/24 is subnetted, 2 subnets C 10.1.2.0 is directly connected, Ethernet0/1 C 10.1.1.0 is directly connected, Ethernet0/0 S* 0.0.0.0/0 [1/0] via 10.1.2.3 [1/0] via 10.1.1.3 Router# The original default gateway is now the backup route. If you want to install the first route as the one to use afte
OSPF overrides "no ip classless"
If you recall our recent thread on this, I was noticing that when ospf would advertise a default route to another router, the receiving router would start to behave classlessly even if 'no ip classless' was in the configuration. This behavior was not seen with eigrp, rip v1, rip v2, igrp, or eigrp; only with ospf. This goes against everything I've read about the differences between 'ip classless' and 'no ip classless'. I initially came to the conclusion that it was a 'feature' of that particular IOS release. Well, I've done some testing with two different features sets of 11.2(25) on a 4000, and I just tested it again on a 2500 running 12.0(16). The same thing happened! Someone out there, puhleez explain to me why OSPF is overriding that command. Shouldn't we be able to leave 'no ip classless' configured if we feel like it? I'm not sure why I'd feel like it, I'm just wondering. Try this out. Connect two routers back to back, A to B. Run anything but OSPF between them at first, and set 'no ip classless' on router B. Configure A to originate a default route. When you see that the gateway of last resort is set on B, try to ping A. That should work just fine. Now try to ping some other unknown subnet of whatever address space you're using. For instance, if your A to B link is 10.1.1.0/24, try to ping 10.50.1.1. You should see five timeouts. If you turn on ip packet debugging, you'll see that the packets were unroutable. Now configure 'ip classless' on router B and try the ping again. You will receive destination unreachable messages from A instead of the timeouts. Debugging will report that they were forwarded to A, as expected. Now configure 'no ip classless' on B again. Remove that routing protocol and run OSPF. When you see the GOLR set on router B, try to ping an unknown subnet again. This time it will behave as if 'ip classless' were configured. Debugging will show that it WAS routable, even though 'no ip classless' will still be in the configuration. Why is this happening? I don't recall seeing this behavior documented. Someone please confirm my findings (and my sanity) or at least point out where my thinking is flawed. Thanks! John ___ Send a cool gift with your E-Card http://www.bluemountain.com/giftcenter/ _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: IP Classless [7:616]
>10.10.32.0 is network address if the 10.0.0.0 network is masked with > 255.0.0.0 Of course, you meant mask 255.255.255.0 :) Which is a common mask, even with network 10.0.0.0 . To KISS it, I would guess that the mask being used is 255.255.0.0 , also a common mask for 10.0.0.0 . One of the router's interfaces is probably ip address 10.10.x.y 255.255.0.0 > ip route 10.0.0.0 255.0.0.0 10.10.32.0 simply says that for all unknown addresses within 10.0.0.0/8 to send them to the router at 10.10.32.0, which he can get to because this is on his (probable) 10.10.x.y link. Note that this will "work" for all addresses within all, even unknown, subnets of 10.0.0.0/8, even with no ip classless set. However, neither no ip classless ip route 8.0.0.0 128.0.0.0 10.10.32.0 nor no ip classless ip route 0.0.0.0 0.0.0.0 10.10.32.0 !(the "classic" default route) would work -- in the sense that any unknown subnet (that is, there are no specific routes that are known to that subnet) address destinations within 10.0.0.0/8 would *not* be sent to 10.10.32.0 . This is because ip classless says do not look at *any* **supernet** routes of the classful network aggregate -- any form of route *within* the classful network *will* be used in the normal "longest-match" way. Unless, of course, as we learned from John, when you're running OSPF, wherein IOS converts to "ip classless" anyway :) (Good, God! I know way too much about "no ip classless" == "ip clueless" (or at least I think I do :) Remember my motto: "Often wrong, but never in doubt." ) ) - Tks| BV | Sr. Technical Consultant, SBM, A Gates/Arrow Co. Vox 770-623-3430 11455 Lakefield Dr. Fax 770-623-3429 Duluth, GA 30097-1511 = -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of EA Louie Sent: Monday, April 09, 2001 3:22 AM To: John Brandis; [EMAIL PROTECTED] Subject: Re: IP Classless no ip classless means route IP over classful boundaries - you'll have to do your homework to learn the Class A, Class B, and Class C network prefixes though, mate ;-) However, 10.0.0.0 is a private (RFC 1918), non-Internet-routeable Class A network the route statement means that the route to network 10.0.0.0 is through IP address 10.10.32.0 (which is kind of weird, because 10.10.32.0 is network address if the 10.0.0.0 network is masked with 255.0.0.0, but with some other subnet masks it would be a network rather than host address) This is a classful static route, which is consistent with the no ip classless command. -e- - Original Message - From: "John Brandis" To: Sent: Sunday, April 08, 2001 8:07 PM Subject: IP Classless > no ip classless > ip route 10.0.0.0 255.0.0.0 10.10.32.0 > > Whats this mean > > Thanks Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=616&t=616 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
no ip classless [7:7100]
In what situation would you use the command "no ip classless"? Cisco's site says ip classless --- This command allows the software to forward packets that are destined for unrecognized subnets of directly connected networks. The packets are forwarded to the best supernet route. no ip classless --- When this feature is disabled, the software discards the packets when a router receives packets for a subnet that numerically falls within its subnetwork addressing scheme, if there is no such subnet number in the routing table and there is no network default route. When would you use this in the real world? Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=7100&t=7100 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
IP classless command [7:30056]
Can anyone please explain to me what is "ip classless" used for? I looked it up on the Caslow book, and it states that by enabling IP classless, it allows one to override the contiguous subnet rule and allow the router to look for the longest match beyond the listed subnets. But I still don't understand what it means? Can anyone give me some examples? Thanks in advance. Best Regards, Hunt Lee IP Solution Analyst Cable & Wireless Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=30056&t=30056 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: IP classless/Default routes
in my experience with having two default routes on a router, they've load-shared across those two interfaces/links. For example, we had a router with a fibre connection and also a wireless connection. The router had two default routes - one across fibre, one across wireless. The fibre went down and half the packets were getting lost, which screamed "load-sharing" to me. I removed the default route across fibre and it worked fine. Cheers, Em -Original Message- From: Dave Page To: 'Cisco List' Sent: 8/8/00 10:05 AM Subject: IP classless/Default routes In Todd Lammle's book for CCNA 640-407, on p. 202 he has set a default route of BOTH 172.16.40.2 and 172.16.20.1. How does one do this, just enter the IP route command as such, one right after the other (??): ip route 0.0.0.0 0.0.0.0 162.16.40.2 ip route 0.0.0.0 0.0.0.0 162.16.20.1 ??? The reason I ask is that in his book for CCNA 640-507, he states on page 253, "Default routing is used to send packets with a remote destination network not in the routing table to the next hop router. You can only use default routing on stub networks, which means that they have only one exit port out of the network." The two books seem to say contradictory things. Is it because the 507 exam is based on a different IOS? What gives? Dave Page ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: IP classless/Default routes
You are correct, equal cost static routes are load balanced on Cisco routers. That's why in a case like that you would want 1 of the statics to have a higher admin weight assigned to it. So the wireless could be ip route 0.0.0.0 0.0.0.0 172.16.2.10 200 and the fiber could be ip route 0.0.0.0 0.0.0.0 192.168.2.10 The static with the lower admin cost will be installed in the route table until the link goes down. Then the other will be installed. Every routing protocol has an admin weight assigned to it. Static and connected routes also have them. Take a look in the docs and you'll find all the defaults. Kenny - Original Message - From: "Emilia Lambros" <[EMAIL PROTECTED]> To: "'Dave Page '" <[EMAIL PROTECTED]> Cc: <[EMAIL PROTECTED]> Sent: Monday, August 07, 2000 7:55 PM Subject: RE: IP classless/Default routes > in my experience with having two default routes on a router, they've > load-shared across those two interfaces/links. > > For example, we had a router with a fibre connection and also a wireless > connection. The router had two default routes - one across fibre, one > across wireless. The fibre went down and half the packets were getting > lost, which screamed "load-sharing" to me. I removed the default route > across fibre and it worked fine. > > Cheers, > > Em > > > -Original Message- > From: Dave Page > To: 'Cisco List' > Sent: 8/8/00 10:05 AM > Subject: IP classless/Default routes > > > In Todd Lammle's book for CCNA 640-407, on p. 202 he has set a default > route > of BOTH 172.16.40.2 and 172.16.20.1. How does one do this, just enter > the > IP route command as such, one right after the other (??): > > ip route 0.0.0.0 0.0.0.0 162.16.40.2 > ip route 0.0.0.0 0.0.0.0 162.16.20.1 > > ??? > > > The reason I ask is that in his book for CCNA 640-507, he states on page > 253, "Default routing is used to send packets with a remote destination > network not in the routing table to the next hop router. You can only > use > default routing on stub networks, which means that they have only one > exit > port out of the network." > > The two books seem to say contradictory things. Is it because the 507 > exam > is based on a different IOS? What gives? > > > Dave Page > > ___ > UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html > FAQ, list archives, and subscription info: http://www.groupstudy.com > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > ___ > UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html > FAQ, list archives, and subscription info: http://www.groupstudy.com > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: IP classless/Default routes
I believe that is a mistake in Todd's book. You can only have one default gateway set. Otherwise the packet would not know where to send the packet. Duck - Original Message - From: Dave Page <[EMAIL PROTECTED]> To: 'Cisco List' <[EMAIL PROTECTED]> Sent: Monday, August 07, 2000 5:05 PM Subject: IP classless/Default routes > > In Todd Lammle's book for CCNA 640-407, on p. 202 he has set a default route > of BOTH 172.16.40.2 and 172.16.20.1. How does one do this, just enter the > IP route command as such, one right after the other (??): > > ip route 0.0.0.0 0.0.0.0 162.16.40.2 > ip route 0.0.0.0 0.0.0.0 162.16.20.1 > > ??? > > > The reason I ask is that in his book for CCNA 640-507, he states on page > 253, "Default routing is used to send packets with a remote destination > network not in the routing table to the next hop router. You can only use > default routing on stub networks, which means that they have only one exit > port out of the network." > > The two books seem to say contradictory things. Is it because the 507 exam > is based on a different IOS? What gives? > > > Dave Page > > ___ > UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html > FAQ, list archives, and subscription info: http://www.groupstudy.com > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: IP classless/Default routes
Dave, If you have a CCO login check this page out. It explains the differences between Default Gateway, Gateway of last resort, and default network. If you don't have a CCO login, let me know and I will paraphrase the article. Hope this helps. http://www.cisco.com/warp/customer/105/default.html -Original Message- From: Dave Page [mailto:[EMAIL PROTECTED]] Sent: Monday, August 07, 2000 7:05 PM To: 'Cisco List' Subject: IP classless/Default routes In Todd Lammle's book for CCNA 640-407, on p. 202 he has set a default route of BOTH 172.16.40.2 and 172.16.20.1. How does one do this, just enter the IP route command as such, one right after the other (??): ip route 0.0.0.0 0.0.0.0 162.16.40.2 ip route 0.0.0.0 0.0.0.0 162.16.20.1 ??? The reason I ask is that in his book for CCNA 640-507, he states on page 253, "Default routing is used to send packets with a remote destination network not in the routing table to the next hop router. You can only use default routing on stub networks, which means that they have only one exit port out of the network." The two books seem to say contradictory things. Is it because the 507 exam is based on a different IOS? What gives? Dave Page ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: IP classless/Default routes
No, there is nothing incongruous here. You add the static route for the default route which tells the router that "if you don't know where the destination is, just shove it out over here". Lammle has to use the two static route commands because router B is in the middle of two networks. So when router B doesn't know of the destination it has to shove the packet out two sides so that each of the other networks can take a look at it and decide what to do with it. It is this kind of confusion that leads to the use of synamic protocols rather than static routes. Adam Hickey [EMAIL PROTECTED] - Original Message - From: "Dave Page" <[EMAIL PROTECTED]> To: "'Cisco List'" <[EMAIL PROTECTED]> Sent: Monday, August 07, 2000 5:05 PM Subject: IP classless/Default routes > > In Todd Lammle's book for CCNA 640-407, on p. 202 he has set a default route > of BOTH 172.16.40.2 and 172.16.20.1. How does one do this, just enter the > IP route command as such, one right after the other (??): > > ip route 0.0.0.0 0.0.0.0 162.16.40.2 > ip route 0.0.0.0 0.0.0.0 162.16.20.1 > > ??? > > > The reason I ask is that in his book for CCNA 640-507, he states on page > 253, "Default routing is used to send packets with a remote destination > network not in the routing table to the next hop router. You can only use > default routing on stub networks, which means that they have only one exit > port out of the network." > > The two books seem to say contradictory things. Is it because the 507 exam > is based on a different IOS? What gives? > > > Dave Page > > ___ > UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html > FAQ, list archives, and subscription info: http://www.groupstudy.com > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: IP classless/Default routes
In many cases, one can substitute the word "public" for "customer" and get the same info http://www.cisco.com/warp/public/105/default.html best wishes Chuck -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of [EMAIL PROTECTED] Sent: Tuesday, August 08, 2000 8:28 AM To: [EMAIL PROTECTED]; [EMAIL PROTECTED] Subject:RE: IP classless/Default routes Dave, If you have a CCO login check this page out. It explains the differences between Default Gateway, Gateway of last resort, and default network. If you don't have a CCO login, let me know and I will paraphrase the article. Hope this helps. http://www.cisco.com/warp/customer/105/default.html -Original Message- From: Dave Page [mailto:[EMAIL PROTECTED]] Sent: Monday, August 07, 2000 7:05 PM To: 'Cisco List' Subject:IP classless/Default routes In Todd Lammle's book for CCNA 640-407, on p. 202 he has set a default route of BOTH 172.16.40.2 and 172.16.20.1. How does one do this, just enter the IP route command as such, one right after the other (??): ip route 0.0.0.0 0.0.0.0 162.16.40.2 ip route 0.0.0.0 0.0.0.0 162.16.20.1 ??? The reason I ask is that in his book for CCNA 640-507, he states on page 253, "Default routing is used to send packets with a remote destination network not in the routing table to the next hop router. You can only use default routing on stub networks, which means that they have only one exit port out of the network." The two books seem to say contradictory things. Is it because the 507 exam is based on a different IOS? What gives? Dave Page ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: IP classless/Default routes
could be its missing it's weight i.e a weighted default gateway to prevent it dropping the packet if the interface is not up ip route 0.0.0.0 0.0.0.0 162.16.40.2 ip route 0.0.0.0 0.0.0.0 162.16.20.1 3 3 being the weight > -Original Message- > From: Donald B Johnson Jr [SMTP:[EMAIL PROTECTED]] > Sent: Tuesday 08 August 2000 19:15 > To: Dave Page; 'Cisco List' > Subject: Re: IP classless/Default routes > > I believe that is a mistake in Todd's book. You can only have one default > gateway set. > Otherwise the packet would not know where to send the packet. > Duck > - Original Message - > From: Dave Page <[EMAIL PROTECTED]> > To: 'Cisco List' <[EMAIL PROTECTED]> > Sent: Monday, August 07, 2000 5:05 PM > Subject: IP classless/Default routes > > > > > > In Todd Lammle's book for CCNA 640-407, on p. 202 he has set a default > route > > of BOTH 172.16.40.2 and 172.16.20.1. How does one do this, just enter > the > > IP route command as such, one right after the other (??): > > > > ip route 0.0.0.0 0.0.0.0 162.16.40.2 > > ip route 0.0.0.0 0.0.0.0 162.16.20.1 > > > > ??? > > > > > > The reason I ask is that in his book for CCNA 640-507, he states on page > > 253, "Default routing is used to send packets with a remote destination > > network not in the routing table to the next hop router. You can only > use > > default routing on stub networks, which means that they have only one > exit > > port out of the network." > > > > The two books seem to say contradictory things. Is it because the 507 > exam > > is based on a different IOS? What gives? > > > > > > Dave Page > > > > ___ > > UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html > > FAQ, list archives, and subscription info: http://www.groupstudy.com > > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > ___ > UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html > FAQ, list archives, and subscription info: http://www.groupstudy.com > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: IP classless/Default routes
I think you mean Administrative Distance. William Swedberg CCNP CCDP --- Fomes Iain <[EMAIL PROTECTED]> wrote: > could be its missing it's weight > i.e a weighted default gateway to prevent it > dropping the packet if the > interface is not up >ip route 0.0.0.0 0.0.0.0 162.16.40.2 >ip route 0.0.0.0 0.0.0.0 162.16.20.1 3 3 being > the weight > > > -Original Message- > > From: Donald B Johnson Jr > [SMTP:[EMAIL PROTECTED]] > > Sent: Tuesday 08 August 2000 19:15 > > To: Dave Page; 'Cisco List' > > Subject:Re: IP classless/Default routes > > > > I believe that is a mistake in Todd's book. You > can only have one default > > gateway set. > > Otherwise the packet would not know where to send > the packet. > > Duck > > - Original Message - > > From: Dave Page <[EMAIL PROTECTED]> > > To: 'Cisco List' <[EMAIL PROTECTED]> > > Sent: Monday, August 07, 2000 5:05 PM > > Subject: IP classless/Default routes > > > > > > > > > > In Todd Lammle's book for CCNA 640-407, on p. > 202 he has set a default > > route > > > of BOTH 172.16.40.2 and 172.16.20.1. How does > one do this, just enter > > the > > > IP route command as such, one right after the > other (??): > > > > > > ip route 0.0.0.0 0.0.0.0 162.16.40.2 > > > ip route 0.0.0.0 0.0.0.0 162.16.20.1 > > > > > > ??? > > > > > > > > > The reason I ask is that in his book for CCNA > 640-507, he states on page > > > 253, "Default routing is used to send packets > with a remote destination > > > network not in the routing table to the next hop > router. You can only > > use > > > default routing on stub networks, which means > that they have only one > > exit > > > port out of the network." > > > > > > The two books seem to say contradictory things. > Is it because the 507 > > exam > > > is based on a different IOS? What gives? > > > > > > > > > Dave Page > > > > > > ___ > > > UPDATED Posting Guidelines: > http://www.groupstudy.com/list/guide.html > > > FAQ, list archives, and subscription info: > http://www.groupstudy.com > > > Report misconduct and Nondisclosure violations > to [EMAIL PROTECTED] > > > > ___ > > UPDATED Posting Guidelines: > http://www.groupstudy.com/list/guide.html > > FAQ, list archives, and subscription info: > http://www.groupstudy.com > > Report misconduct and Nondisclosure violations to > [EMAIL PROTECTED] > > ___ > UPDATED Posting Guidelines: > http://www.groupstudy.com/list/guide.html > FAQ, list archives, and subscription info: > http://www.groupstudy.com > Report misconduct and Nondisclosure violations to > [EMAIL PROTECTED] > > > = William Swedberg CCNP CCDP __ Do You Yahoo!? Kick off your party with Yahoo! Invites. http://invites.yahoo.com/ ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: IP classless/Default routes
Or you could substitute "public" for "customer" in the URL and get to it anyway. http://www.cisco.com/warp/public/105/default.html Karen E Young Network Engineer ELF Technologies, Inc [EMAIL PROTECTED] dacarl4@uswes t.comTo: [EMAIL PROTECTED], [EMAIL PROTECTED] Sent by: cc: nobody@groups Subject: RE: IP classless/Default routes tudy.com 08/08/00 08:28 AM Please respond to dacarl4 Dave, If you have a CCO login check this page out. It explains the differences between Default Gateway, Gateway of last resort, and default network. If you don't have a CCO login, let me know and I will paraphrase the article. Hope this helps. http://www.cisco.com/warp/customer/105/default.html -Original Message- From: Dave Page [mailto:[EMAIL PROTECTED]] Sent: Monday, August 07, 2000 7:05 PM To:'Cisco List' Subject:IP classless/Default routes In Todd Lammle's book for CCNA 640-407, on p. 202 he has set a default route of BOTH 172.16.40.2 and 172.16.20.1. How does one do this, just enter the IP route command as such, one right after the other (??): ip route 0.0.0.0 0.0.0.0 162.16.40.2 ip route 0.0.0.0 0.0.0.0 162.16.20.1 ??? The reason I ask is that in his book for CCNA 640-507, he states on page 253, "Default routing is used to send packets with a remote destination network not in the routing table to the next hop router. You can only use default routing on stub networks, which means that they have only one exit port out of the network." The two books seem to say contradictory things. Is it because the 507 exam is based on a different IOS? What gives? Dave Page ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: IP classless/Default routes
Actually, I believe this is incorrect. If you enter two static default routes with the same administrative distance (in this case 1) then (depending on any configured maximum paths statement, I believe the default is 4) the router will load balance using both addresses. If the router will load balance on per-packet or per-destination basis will depend on the switching method used. The reason one of your default routes dissapear when you disconnect one of your ethernet segments is that the route to your next hop address for that default route dissapears. If a router does not have a route to the next hop address then it will not install that route into the route table even though it is statically configured. To test this scenario using your previous example try adding a static route to 10.1.1.0 255.255.255.0 with a next hop address of 10.1.2.3. When both ethernet interfaces are up you won't see that new static route for 10.1.1.3 in the table because the administrative distance for that route is 1. The router as a connected route with an administrative distance of 0 out it's ethernet interface for that network. As soon as you remove the cable from the ethernet interface with 10.1.1.1 connected to it (e0/0) the static route for 10.1.1.0 255.255.255.0 with next hop 10.1.2.3 will show up. At the same time both default statics will remain in the routing table and be used in a load sharing state. Michael Cohen CCDP, CCNP CCIE #6080 -Original Message- From: Donald B Johnson Jr [mailto:[EMAIL PROTECTED]] Sent: Tuesday, August 08, 2000 3:02 PM To: [EMAIL PROTECTED]; Dave Page Subject: IP classless/Default routes Dave Let me clear this up a little, you can place more than one default route in the routing table but the router will only use the first entry. If that link goes down the next default route will be used. Here is the config, interface Ethernet0/0 ip address 10.1.1.1 255.255.255.0 no ip directed-broadcast interface Ethernet0/1 ip address 10.1.2.1 255.255.255.0 no ip directed-broadcast Router#conf Configuring from terminal, memory, or network [terminal]? Enter configuration commands, one per line. End with CNTL/Z. Router(config)#ip routing Router(config)#ip route 0.0.0.0 0.0.0.0 10.1.1.3 Router(config)#ip route 0.0.0.0 0.0.0.0 10.1.2.3 Router(config)#^Z Router# 00:08:49: %SYS-5-CONFIG_I: Configured from console by console Router#sh ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default U - per-user static route, o - ODR Gateway of last resort is 10.1.1.3 to network 0.0.0.0 10.0.0.0/24 is subnetted, 2 subnets C 10.1.2.0 is directly connected, Ethernet0/1 C 10.1.1.0 is directly connected, Ethernet0/0 S* 0.0.0.0/0 [1/0] via 10.1.1.3 [1/0] via 10.1.2.3 Router# Notice that the first ip route entry is the Gateway of last resort. Now watch what happens when I disconnect the cable to E0/0 Router# 00:15:20: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0/0, changed s tate to down Router#sh ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default U - per-user static route, o - ODR Gateway of last resort is 10.1.2.3 to network 0.0.0.0 10.0.0.0/24 is subnetted, 1 subnets C 10.1.2.0 is directly connected, Ethernet0/1 S* 0.0.0.0/0 [1/0] via 10.1.2.3 Router# Now notice that the second ip route entry is the Gateway of last resort. Now watch what happens when I reconnect the E0/0 cable. Router# 00:19:27: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0/0, changed s tate to up Router#sh ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default U - per-user static route, o - ODR Gateway of last resort is 10.1.2.3 to network 0.0.0.0 10.0.0.0/24 is subnetted, 2 subnets C 10.1.2.0 is directly connected, Ethernet0/1 C 10.1.1.0 is directly connected, Ethernet0/0 S* 0.0.0.0/0 [1/0] via 10.1.2.3 [1/0] via 10.1.1.3 Router# The original default gateway is now the backup route. If you want to install the first route as the one to use afte
RE: IP classless/Default routes
Usually, you can substitute 'public' for 'customer' if the document is publicly available (which this one is) http://www.cisco.com/warp/public/105/default.html Bob -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of [EMAIL PROTECTED] Sent: Tuesday, August 08, 2000 11:28 AM To: [EMAIL PROTECTED]; [EMAIL PROTECTED] Subject: RE: IP classless/Default routes Dave, If you have a CCO login check this page out. It explains the differences between Default Gateway, Gateway of last resort, and default network. If you don't have a CCO login, let me know and I will paraphrase the article. Hope this helps. http://www.cisco.com/warp/customer/105/default.html -Original Message- From: Dave Page [mailto:[EMAIL PROTECTED]] Sent: Monday, August 07, 2000 7:05 PM To: 'Cisco List' Subject:IP classless/Default routes In Todd Lammle's book for CCNA 640-407, on p. 202 he has set a default route of BOTH 172.16.40.2 and 172.16.20.1. How does one do this, just enter the IP route command as such, one right after the other (??): ip route 0.0.0.0 0.0.0.0 162.16.40.2 ip route 0.0.0.0 0.0.0.0 162.16.20.1 ??? The reason I ask is that in his book for CCNA 640-507, he states on page 253, "Default routing is used to send packets with a remote destination network not in the routing table to the next hop router. You can only use default routing on stub networks, which means that they have only one exit port out of the network." The two books seem to say contradictory things. Is it because the 507 exam is based on a different IOS? What gives? Dave Page ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: ip classless, Not exactly correct
At 08:41 PM 09/24/2000 -0500, Yee, Jason wrote: >With this command if a route is not found in the routing table it will take >the gateway of last resort if it is set . > >Without this command it will just drop the packet if a classful route is not >found in the routing table. > >Jason > Without the IP classless command a router sees routes as classful So lets say you on your router you have a serial interface with the address 10.0.0.1 /30 and an ethernet with the address 220.110.60.1 and a default route pointing out the serial interface Without the ip classless command if someone on the 220.110.60 network is trying to reach 10.10.10.10 (which does not fall within the 10.0.0.0 /30 network) then the router would see that it had a piece of the 10 net on it and assume it should be able to access the whole 10 net, but actually only knowing a route to 10.0.0.0 /30 it would drop the packet If you were trying to reach 11.0.0.1 if would forward the packet out the serial as per the default route because it doesn't already know a route to a piece of that class A. With ip classless in place traffic is routed based on its stated network address, AKA CIDR. ip classless is the way to go! Without it you're generally asking for trouble, especially if your ISP uses any class A or B address space. also if you plan on using the zero net of any classfull address then you'll also need the command ip subnet-zero my $.02 Tom Pruneau Trainer Network Operations GENUITY 3 Van de Graff Drive Burlington Ma. 01803 24 Hr. Network Operations Center 800-436-8489 If you need to get a hold of me my hours are 7AM-3PM ET Mon-Fri --- This email is composed of 82% post consumer recycled data bits --- "Once in a while you get shown the light in the strangest of places if you look at it right" **NOTE: New CCNA/CCDA List has been formed. For more information go to http://www.groupstudy.com/list/Associates.html _ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: IP Classless Revisited (More info)
Okay, I just tried this with RIP advertising the default route and I'm even more confused! Now, it behaves as I would expect. With no ip classless, pings to unknown 10.x.x.x subnets are unroutable even though there is a default route in the routing table. With no ip classless, why does my router take the default route when it was installed by OSPF but not when it was installed by RIP? I would expect it to never take the default route for 10.x.x.x addresses with no ip classless. This really concerns me because I was taking a practice CCIE written exam a few days ago and ran across a question like this and I answered the question assuming normal behavior of no ip classless and got it right. Now I'm thinking there are some more twists to its behavior that i'm not aware of. John > Sure, I'll try that but I don't see why it should matter. As I understand > it, ip classless affects routing table lookups only and it doesn't care how > those routes were installed into the table. > > Although, given this behavior, my assumption might be wrong. > > Thanks, > John > > > John, > > Interesting. I think this is due to OSPF, not redistribution problem. > Can you try running RIP instead of OSPF ? > > > > Cheers, > > YY > > > > > > > > -Original Message- > > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of > > John Neiberger > > Sent: Sunday, March 25, 2001 5:28 AM > > To: [EMAIL PROTECTED] > > Subject: IP Classless Revisited (this is just odd...) > > > > > > Ok, just when you thought it was safe to go back in the water Or > should > > I say, just when I thought I understood the behavior of 'ip classess' and > > 'no ip classless'.... Let me summarize my lab setup. > > > > RouterA-RouterB--RouterC > > > > Pretty simple. AtoB is 10.1.1.0/24, BtoA is 10.1.2.0/24. OSPF is > running > > on both links. 'ip classless' is on A and C, but not B initially. On B > I > > see these routes: > > > > 10.0.0.0/24 is subnetted, 2 subnets > > C 10.1.2.0 is directly connected, Serial1 > > C 10.1.1.0 is directly connected, Serial0 > > > > That's what I expect to see. Then I add a default route on B, 'ip route > > 0.0.0.0 0.0.0.0 10.1.1.2'. With no ip classless configured, any packets > to > > unknown subnets of 10.0.0.0/8 should be dropped. I tested it and that is > > the case. With 'ip classless' configured, and unknown packets regardless > of > > major network get routed to 10.1.1.2. > > > > Now here is what I don't understand. Let's turn off ip classless on B > > again, then go to Router C and add a default route to null0 and > > default-information originate to the ospf process. I now see this in > router > > B: > > > > 10.0.0.0/24 is subnetted, 2 subnets > > C 10.1.2.0 is directly connected, Serial1 > > C 10.1.1.0 is directly connected, Serial0 > > O*E2 0.0.0.0/0 [110/1] via 10.1.2.2, 00:06:38, Serial1 > > > > There is indeed a default route. With no ip classless configured, I > would > > expect the same behavior as before. If I were to ping 10.5.5.5 the > packets > > should be unroutable, but they're not! They get routed to the default > route > > whether or not ip classless is configured. > > > > Why is a default route learned through a routing protocol treated > > differently than a manually configured default route? I went through > this > > entire process twice and I just don't understand the behavior. > > > > What am I missing? I know it's going to be something obvious, but I > don't > > see it yet. > > > > Ok, I just now tried this: with the ospf external default route still in > > the routing table, I pinged 10.5.5.5 and it took the default route. Then > I > > manually added a default static route and the destination became > unroutable > > due to 'no ip classless' being configured. Removing the static default > it > > becomes routable again. > > > > Weird. What's going on? > > > > Thanks, > > John > > > > > > > > > > > > ___ > > Send a cool gift with your E-Card > > http://www.bluemountain.com/giftcenter/ > > > >
Re: IP Classless Revisited (More info)
I guess in faovour of metric. "John Neiberger" <[EMAIL PROTECTED]> ¼¶¼g©ó¶l¥ó [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Okay, I just tried this with RIP advertising the default route and I'm even > more confused! Now, it behaves as I would expect. With no ip classless, > pings to unknown 10.x.x.x subnets are unroutable even though there is a > default route in the routing table. > > With no ip classless, why does my router take the default route when it was > installed by OSPF but not when it was installed by RIP? I would expect it > to never take the default route for 10.x.x.x addresses with no ip classless. > > This really concerns me because I was taking a practice CCIE written exam a > few days ago and ran across a question like this and I answered the question > assuming normal behavior of no ip classless and got it right. Now I'm > thinking there are some more twists to its behavior that i'm not aware of. > > John > > > Sure, I'll try that but I don't see why it should matter. As I > understand > > it, ip classless affects routing table lookups only and it doesn't care > how > > those routes were installed into the table. > > > > Although, given this behavior, my assumption might be wrong. > > > > Thanks, > > John > > > > > John, > > > Interesting. I think this is due to OSPF, not redistribution problem. > > > Can you try running RIP instead of OSPF ? > > > > > > Cheers, > > > YY > > > > > > > > > > > > -Original Message- > > > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of > > > John Neiberger > > > Sent: Sunday, March 25, 2001 5:28 AM > > > To: [EMAIL PROTECTED] > > > Subject: IP Classless Revisited (this is just odd...) > > > > > > > > > Ok, just when you thought it was safe to go back in the water Or > > should > > > I say, just when I thought I understood the behavior of 'ip classess' > and > > > 'no ip classless' Let me summarize my lab setup. > > > > > > RouterA-RouterB--RouterC > > > > > > Pretty simple. AtoB is 10.1.1.0/24, BtoA is 10.1.2.0/24. OSPF is > > running > > > on both links. 'ip classless' is on A and C, but not B initially. On > B > > I > > > see these routes: > > > > > > 10.0.0.0/24 is subnetted, 2 subnets > > > C 10.1.2.0 is directly connected, Serial1 > > > C 10.1.1.0 is directly connected, Serial0 > > > > > > That's what I expect to see. Then I add a default route on B, 'ip > route > > > 0.0.0.0 0.0.0.0 10.1.1.2'. With no ip classless configured, any > packets > > to > > > unknown subnets of 10.0.0.0/8 should be dropped. I tested it and that > is > > > the case. With 'ip classless' configured, and unknown packets > regardless > > of > > > major network get routed to 10.1.1.2. > > > > > > Now here is what I don't understand. Let's turn off ip classless on B > > > again, then go to Router C and add a default route to null0 and > > > default-information originate to the ospf process. I now see this in > > router > > > B: > > > > > > 10.0.0.0/24 is subnetted, 2 subnets > > > C 10.1.2.0 is directly connected, Serial1 > > > C 10.1.1.0 is directly connected, Serial0 > > > O*E2 0.0.0.0/0 [110/1] via 10.1.2.2, 00:06:38, Serial1 > > > > > > There is indeed a default route. With no ip classless configured, I > > would > > > expect the same behavior as before. If I were to ping 10.5.5.5 the > > packets > > > should be unroutable, but they're not! They get routed to the default > > route > > > whether or not ip classless is configured. > > > > > > Why is a default route learned through a routing protocol treated > > > differently than a manually configured default route? I went through > > this > > > entire process twice and I just don't understand the behavior. > > > > > > What am I missing? I know it's going to be something obvious, but I > > don't > > > see it yet. > > > > > > Ok, I just now tried this: with the ospf external default route still > in > > > the routing table, I pinged 10.5.5
Re: IP Classless Revisited (More info)
Metric shouldn't have anything to do with it. Whether I'm using RIP or OSPF the default route is being added to the routing table of the hub router. The issue is that with no ip classless configured, the hub router should NOT ever pick the default route when trying to reach unknown subnets of the 10.x.x.x network. In my case, when RIP installed the default route it behaves correctly. When OSPF installed the route it behaved as if 'ip classless' were configured. Very odd. John > I guess in faovour of metric. > > "John Neiberger" <[EMAIL PROTECTED]> ¼¶¼g©ó¶l¥ó > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > Okay, I just tried this with RIP advertising the default route and I'm > even > > more confused! Now, it behaves as I would expect. With no ip classless, > > pings to unknown 10.x.x.x subnets are unroutable even though there is a > > default route in the routing table. > > > > With no ip classless, why does my router take the default route when it > was > > installed by OSPF but not when it was installed by RIP? I would expect it > > to never take the default route for 10.x.x.x addresses with no ip > classless. > > > > This really concerns me because I was taking a practice CCIE written exam > a > > few days ago and ran across a question like this and I answered the > question > > assuming normal behavior of no ip classless and got it right. Now I'm > > thinking there are some more twists to its behavior that i'm not aware of. > > > > John > > > > > Sure, I'll try that but I don't see why it should matter. As I > > understand > > > it, ip classless affects routing table lookups only and it doesn't care > > how > > > those routes were installed into the table. > > > > > > Although, given this behavior, my assumption might be wrong. > > > > > > Thanks, > > > John > > > > > > > John, > > > > Interesting. I think this is due to OSPF, not redistribution > problem. > > > > > Can you try running RIP instead of OSPF ? > > > > > > > > Cheers, > > > > YY > > > > > > > > > > > > > > > > -Original Message- > > > > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf > Of > > > > John Neiberger > > > > Sent: Sunday, March 25, 2001 5:28 AM > > > > To: [EMAIL PROTECTED] > > > > Subject: IP Classless Revisited (this is just odd...) > > > > > > > > > > > > Ok, just when you thought it was safe to go back in the water Or > > > should > > > > I say, just when I thought I understood the behavior of 'ip > classess' > > and > > > > 'no ip classless' Let me summarize my lab setup. > > > > > > > > RouterA-RouterB--RouterC > > > > > > > > Pretty simple. AtoB is 10.1.1.0/24, BtoA is 10.1.2.0/24. OSPF is > > > running > > > > on both links. 'ip classless' is on A and C, but not B initially. > On > > B > > > I > > > > see these routes: > > > > > > > > 10.0.0.0/24 is subnetted, 2 subnets > > > > C 10.1.2.0 is directly connected, Serial1 > > > > C 10.1.1.0 is directly connected, Serial0 > > > > > > > > That's what I expect to see. Then I add a default route on B, 'ip > > route > > > > 0.0.0.0 0.0.0.0 10.1.1.2'. With no ip classless configured, any > > packets > > > to > > > > unknown subnets of 10.0.0.0/8 should be dropped. I tested it and > that > > is > > > > the case. With 'ip classless' configured, and unknown packets > > regardless > > > of > > > > major network get routed to 10.1.1.2. > > > > > > > > Now here is what I don't understand. Let's turn off ip classless on > B > > > > again, then go to Router C and add a default route to null0 and > > > > default-information originate to the ospf process. I now see this > in > > > router > > > > B: > > > > > > > > 10.0.0.0/24 is subnetted, 2 subnets > > > > C 10.1.2.0 is directly connected, Serial1 > > > > C 10.1.1.0
RE: IP Classless Revisited (More info)
Bug? -- or "feature" as you say :)
What was really telling to me was when you added the static default
route on top of the OSPF-installed default. The higher admin distance
made the static route be preferred and the routing process behaved
"normally" ("classfully").
Perhaps the feature is :
Hmmm. I see this OSPF installed route. I guess he *really* wants to
run
classlessly, else he'd be running some older protocol !
But you'd think that the code never even gets to any the supernet of
10.5.0.0.
It would really have to be written in to look for OSPF routes before
behaving classfully.
I wonder what would happen if you advertised 8.0.0.0 (being a "supernet
of 10.0.0.0) from C instead of 0.0.0.0 :) -- to see if it's a general
behavior or specifically looking for 0.0.0.0.
-
Tks | <mailto:[EMAIL PROTECTED]>
BV | <mailto:[EMAIL PROTECTED]>
Sr. Technical Consultant, SBM, A Gates/Arrow Co.
Vox 770-623-3430 11455 Lakefield Dr.
Fax 770-623-3429 Duluth, GA 30097-1511
=
-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of
John Neiberger
Sent: Sunday, March 25, 2001 1:32 PM
To: Vincent
Cc: [EMAIL PROTECTED]
Subject: Re: IP Classless Revisited (More info)
Metric shouldn't have anything to do with it. Whether I'm using RIP or
OSPF
the default route is being added to the routing table of the hub router.
The issue is that with no ip classless configured, the hub router should
NOT
ever pick the default route when trying to reach unknown subnets of the
10.x.x.x network.
In my case, when RIP installed the default route it behaves correctly.
When
OSPF installed the route it behaved as if 'ip classless' were
configured.
Very odd.
John
> I guess in faovour of metric.
>
> "John Neiberger" <[EMAIL PROTECTED]> ¼¶¼g©ó¶l¥ó
> [EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> > Okay, I just tried this with RIP advertising the default route and
I'm
> even
> > more confused! Now, it behaves as I would expect. With no ip
classless,
> > pings to unknown 10.x.x.x subnets are unroutable even though there
is a
> > default route in the routing table.
> >
> > With no ip classless, why does my router take the default route
when it
> was
> > installed by OSPF but not when it was installed by RIP? I would
expect
it
> > to never take the default route for 10.x.x.x addresses with no ip
> classless.
> >
> > This really concerns me because I was taking a practice CCIE
written
exam
> a
> > few days ago and ran across a question like this and I answered the
> question
> > assuming normal behavior of no ip classless and got it right. Now
I'm
> > thinking there are some more twists to its behavior that i'm not
aware
of.
> >
> > John
> >
> > > Sure, I'll try that but I don't see why it should matter. As I
> > understand
> > > it, ip classless affects routing table lookups only and it
doesn't
care
> > how
> > > those routes were installed into the table.
> > >
> > > Although, given this behavior, my assumption might be wrong.
> > >
> > > Thanks,
> > > John
> > >
> > > > John,
> > > > Interesting. I think this is due to OSPF, not redistribution
> problem.
> >
> > > Can you try running RIP instead of OSPF ?
> > > >
> > > > Cheers,
> > > > YY
> > > >
> > > >
> > > >
> > > > -Original Message-----
> > > > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On
Behalf
> Of
> > > > John Neiberger
> > > > Sent: Sunday, March 25, 2001 5:28 AM
> > > > To: [EMAIL PROTECTED]
> > > > Subject: IP Classless Revisited (this is just odd...)
> > > >
> > > >
> > > > Ok, just when you thought it was safe to go back in the
water
Or
> > > should
> > > > I say, just when I thought I understood the behavior of 'ip
> classess'
> > and
> > > > 'no ip classless' Let me summarize my lab setup.
> > > >
> > > > RouterA-RouterB--RouterC
> > > >
> > > > Pretty simple. AtoB is 10.1.1.0/24, BtoA is 10.1.2.0/24.
OSPF
is
> > > running
> > > > on both links. 'ip classless' is on A and C, but not B
initially.
> On
> > B
> > > I
> >
RE: IP Classless Revisited (More info)
That would be a good test, actually. I think your summarization of the "feature" is
right on. It's almost as if the router thinks "Well, we're running OSPF so *surely*
he must not *really* want 'no ip classless' turned on. So I'll go ahead and operate
classlessly anyway."
This is definitely pretty odd. I think tonight when I get home I'll rearrange my
setup so that instead of doing this on a 4000 running 11.2(25a), I'll use a 2501
running 12.0(16). Perhaps this really is a feature that was fixed in later releases.
Thanks,
John
>>> "Bob Vance" <[EMAIL PROTECTED]> 3/26/01 9:23:46 AM >>>
Bug? -- or "feature" as you say :)
What was really telling to me was when you added the static default
route on top of the OSPF-installed default. The higher admin distance
made the static route be preferred and the routing process behaved
"normally" ("classfully").
Perhaps the feature is :
Hmmm. I see this OSPF installed route. I guess he *really* wants to
run
classlessly, else he'd be running some older protocol !
But you'd think that the code never even gets to any the supernet of
10.5.0.0.
It would really have to be written in to look for OSPF routes before
behaving classfully.
I wonder what would happen if you advertised 8.0.0.0 (being a "supernet
of 10.0.0.0) from C instead of 0.0.0.0 :) -- to see if it's a general
behavior or specifically looking for 0.0.0.0.
-
Tks| <mailto:[EMAIL PROTECTED]>
BV | <mailto:[EMAIL PROTECTED]>
Sr. Technical Consultant, SBM, A Gates/Arrow Co.
Vox 770-623-3430 11455 Lakefield Dr.
Fax 770-623-3429 Duluth, GA 30097-1511
=
-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of
John Neiberger
Sent: Sunday, March 25, 2001 1:32 PM
To: Vincent
Cc: [EMAIL PROTECTED]
Subject: Re: IP Classless Revisited (More info)
Metric shouldn't have anything to do with it. Whether I'm using RIP or
OSPF
the default route is being added to the routing table of the hub router.
The issue is that with no ip classless configured, the hub router should
NOT
ever pick the default route when trying to reach unknown subnets of the
10.x.x.x network.
In my case, when RIP installed the default route it behaves correctly.
When
OSPF installed the route it behaved as if 'ip classless' were
configured.
Very odd.
John
> I guess in faovour of metric.
>
> "John Neiberger" <[EMAIL PROTECTED]> ¼¶¼g©ó¶l¥ó
> [EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> > Okay, I just tried this with RIP advertising the default route and
I'm
> even
> > more confused! Now, it behaves as I would expect. With no ip
classless,
> > pings to unknown 10.x.x.x subnets are unroutable even though there
is a
> > default route in the routing table.
> >
> > With no ip classless, why does my router take the default route
when it
> was
> > installed by OSPF but not when it was installed by RIP? I would
expect
it
> > to never take the default route for 10.x.x.x addresses with no ip
> classless.
> >
> > This really concerns me because I was taking a practice CCIE
written
exam
> a
> > few days ago and ran across a question like this and I answered the
> question
> > assuming normal behavior of no ip classless and got it right. Now
I'm
> > thinking there are some more twists to its behavior that i'm not
aware
of.
> >
> > John
> >
> > > Sure, I'll try that but I don't see why it should matter. As I
> > understand
> > > it, ip classless affects routing table lookups only and it
doesn't
care
> > how
> > > those routes were installed into the table.
> > >
> > > Although, given this behavior, my assumption might be wrong.
> > >
> > > Thanks,
> > > John
> > >
> > > > John,
> > > > Interesting. I think this is due to OSPF, not redistribution
> problem.
> >
> > > Can you try running RIP instead of OSPF ?
> > > >
> > > > Cheers,
> > > > YY
> > > >
> > > >
> > > >
> > > > -Original Message-
> > > > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On
Behalf
> Of
> > > > John Neiberger
> > > > Sent: Sunday, March 25, 2001 5:28 AM
> > > > To: [EMAIL PROTECTED]
> > > > Subject: IP Classless Revisited (this is just odd...)
> > > >
> > > &g
More Info (OSPF and IP Classless)
Here is a link verifying that my understanding of 'no ip classless' is correct! http://www.cisco.com/warp/public/105/21.html So, referring to my other threads, why is OSPF overriding classfull routing table lookups? I'd rather not retype the whole thing, so if you'd like the details of my experiments, refer to the other threads. I just wanted to post this link to show that I wasn't entirely crazy! Maybe a little, but not entirely. Regards, John the Not-entirely Insane (formerly John the Cheerful, PKA John the Monday Grump) ___ Send a cool gift with your E-Card http://www.bluemountain.com/giftcenter/ _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: OSPF overrides "no ip classless"
John, did you ever try distributing route for 8.0.0.0 instead of 0.0.0.0 to see whether it was true for all routes or just the clammy "normal", "default" default route :) ? - Tks | <mailto:[EMAIL PROTECTED]> BV | <mailto:[EMAIL PROTECTED]> Sr. Technical Consultant, SBM, A Gates/Arrow Co. Vox 770-623-3430 11455 Lakefield Dr. Fax 770-623-3429 Duluth, GA 30097-1511 = -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of John Neiberger Sent: Tuesday, March 27, 2001 11:19 PM To: [EMAIL PROTECTED] Subject: OSPF overrides "no ip classless" If you recall our recent thread on this, I was noticing that when ospf would advertise a default route to another router, the receiving router would start to behave classlessly even if 'no ip classless' was in the configuration. This behavior was not seen with eigrp, rip v1, rip v2, igrp, or eigrp; only with ospf. This goes against everything I've read about the differences between 'ip classless' and 'no ip classless'. I initially came to the conclusion that it was a 'feature' of that particular IOS release. Well, I've done some testing with two different features sets of 11.2(25) on a 4000, and I just tested it again on a 2500 running 12.0(16). The same thing happened! Someone out there, puhleez explain to me why OSPF is overriding that command. Shouldn't we be able to leave 'no ip classless' configured if we feel like it? I'm not sure why I'd feel like it, I'm just wondering. Try this out. Connect two routers back to back, A to B. Run anything but OSPF between them at first, and set 'no ip classless' on router B. Configure A to originate a default route. When you see that the gateway of last resort is set on B, try to ping A. That should work just fine. Now try to ping some other unknown subnet of whatever address space you're using. For instance, if your A to B link is 10.1.1.0/24, try to ping 10.50.1.1. You should see five timeouts. If you turn on ip packet debugging, you'll see that the packets were unroutable. Now configure 'ip classless' on router B and try the ping again. You will receive destination unreachable messages from A instead of the timeouts. Debugging will report that they were forwarded to A, as expected. Now configure 'no ip classless' on B again. Remove that routing protocol and run OSPF. When you see the GOLR set on router B, try to ping an unknown subnet again. This time it will behave as if 'ip classless' were configured. Debugging will show that it WAS routable, even though 'no ip classless' will still be in the configuration. Why is this happening? I don't recall seeing this behavior documented. Someone please confirm my findings (and my sanity) or at least point out where my thinking is flawed. Thanks! John ___ Send a cool gift with your E-Card http://www.bluemountain.com/giftcenter/ _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: OSPF overrides "no ip classless"
Now that I think about it, I believe I did try 10.0.0.0/8 and it still behaved classfully, even running OSPF. I'll try it again to make sure, though. I'm only 30 and my memory is already failing me. John >>> "Bob Vance" <[EMAIL PROTECTED]> 3/28/01 8:34:49 AM >>> John, did you ever try distributing route for 8.0.0.0 instead of 0.0.0.0 to see whether it was true for all routes or just the clammy "normal", "default" default route :) ? - Tks| <mailto:[EMAIL PROTECTED]> BV | <mailto:[EMAIL PROTECTED]> Sr. Technical Consultant, SBM, A Gates/Arrow Co. Vox 770-623-3430 11455 Lakefield Dr. Fax 770-623-3429 Duluth, GA 30097-1511 = -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of John Neiberger Sent: Tuesday, March 27, 2001 11:19 PM To: [EMAIL PROTECTED] Subject: OSPF overrides "no ip classless" If you recall our recent thread on this, I was noticing that when ospf would advertise a default route to another router, the receiving router would start to behave classlessly even if 'no ip classless' was in the configuration. This behavior was not seen with eigrp, rip v1, rip v2, igrp, or eigrp; only with ospf. This goes against everything I've read about the differences between 'ip classless' and 'no ip classless'. I initially came to the conclusion that it was a 'feature' of that particular IOS release. Well, I've done some testing with two different features sets of 11.2(25) on a 4000, and I just tested it again on a 2500 running 12.0(16). The same thing happened! Someone out there, puhleez explain to me why OSPF is overriding that command. Shouldn't we be able to leave 'no ip classless' configured if we feel like it? I'm not sure why I'd feel like it, I'm just wondering. Try this out. Connect two routers back to back, A to B. Run anything but OSPF between them at first, and set 'no ip classless' on router B. Configure A to originate a default route. When you see that the gateway of last resort is set on B, try to ping A. That should work just fine. Now try to ping some other unknown subnet of whatever address space you're using. For instance, if your A to B link is 10.1.1.0/24, try to ping 10.50.1.1. You should see five timeouts. If you turn on ip packet debugging, you'll see that the packets were unroutable. Now configure 'ip classless' on router B and try the ping again. You will receive destination unreachable messages from A instead of the timeouts. Debugging will report that they were forwarded to A, as expected. Now configure 'no ip classless' on B again. Remove that routing protocol and run OSPF. When you see the GOLR set on router B, try to ping an unknown subnet again. This time it will behave as if 'ip classless' were configured. Debugging will show that it WAS routable, even though 'no ip classless' will still be in the configuration. Why is this happening? I don't recall seeing this behavior documented. Someone please confirm my findings (and my sanity) or at least point out where my thinking is flawed. Thanks! John ___ Send a cool gift with your E-Card http://www.bluemountain.com/giftcenter/ _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: OSPF overrides "no ip classless"
And 8.0.0.0 is in that magic "in-between" place of being a supernet but not the "normal" default route. - Tks | <mailto:[EMAIL PROTECTED]> BV | <mailto:[EMAIL PROTECTED]> Sr. Technical Consultant, SBM, A Gates/Arrow Co. Vox 770-623-3430 11455 Lakefield Dr. Fax 770-623-3429 Duluth, GA 30097-1511 = -Original Message- From: John Neiberger [mailto:[EMAIL PROTECTED]] Sent: Wednesday, March 28, 2001 5:06 PM To: [EMAIL PROTECTED] Cc: [EMAIL PROTECTED] Subject: RE: OSPF overrides "no ip classless" Now that I think about it, I believe I did try 10.0.0.0/8 and it still behaved classfully, even running OSPF. I'll try it again to make sure, though. I'm only 30 and my memory is already failing me. John >>> "Bob Vance" <[EMAIL PROTECTED]> 3/28/01 8:34:49 AM >>> John, did you ever try distributing route for 8.0.0.0 instead of 0.0.0.0 to see whether it was true for all routes or just the clammy "normal", "default" default route :) ? - Tks| <mailto:[EMAIL PROTECTED]> BV | <mailto:[EMAIL PROTECTED]> Sr. Technical Consultant, SBM, A Gates/Arrow Co. Vox 770-623-3430 11455 Lakefield Dr. Fax 770-623-3429 Duluth, GA 30097-1511 = -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of John Neiberger Sent: Tuesday, March 27, 2001 11:19 PM To: [EMAIL PROTECTED] Subject: OSPF overrides "no ip classless" If you recall our recent thread on this, I was noticing that when ospf would advertise a default route to another router, the receiving router would start to behave classlessly even if 'no ip classless' was in the configuration. This behavior was not seen with eigrp, rip v1, rip v2, igrp, or eigrp; only with ospf. This goes against everything I've read about the differences between 'ip classless' and 'no ip classless'. I initially came to the conclusion that it was a 'feature' of that particular IOS release. Well, I've done some testing with two different features sets of 11.2(25) on a 4000, and I just tested it again on a 2500 running 12.0(16). The same thing happened! Someone out there, puhleez explain to me why OSPF is overriding that command. Shouldn't we be able to leave 'no ip classless' configured if we feel like it? I'm not sure why I'd feel like it, I'm just wondering. Try this out. Connect two routers back to back, A to B. Run anything but OSPF between them at first, and set 'no ip classless' on router B. Configure A to originate a default route. When you see that the gateway of last resort is set on B, try to ping A. That should work just fine. Now try to ping some other unknown subnet of whatever address space you're using. For instance, if your A to B link is 10.1.1.0/24, try to ping 10.50.1.1. You should see five timeouts. If you turn on ip packet debugging, you'll see that the packets were unroutable. Now configure 'ip classless' on router B and try the ping again. You will receive destination unreachable messages from A instead of the timeouts. Debugging will report that they were forwarded to A, as expected. Now configure 'no ip classless' on B again. Remove that routing protocol and run OSPF. When you see the GOLR set on router B, try to ping an unknown subnet again. This time it will behave as if 'ip classless' were configured. Debugging will show that it WAS routable, even though 'no ip classless' will still be in the configuration. Why is this happening? I don't recall seeing this behavior documented. Someone please confirm my findings (and my sanity) or at least point out where my thinking is flawed. Thanks! John ___ Send a cool gift with your E-Card http://www.bluemountain.com/giftcenter/ _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: OSPF overrides "no ip classless"
>Now that I think about it, I believe I did try 10.0.0.0/8 and it still >behaved classfully, even running OSPF. I'll try it again to make sure, >though. I'm only 30 and my memory is already failing me. > >John I'll bet your memory isn't from a Cisco-approved supplier. See what happens? > "Bob Vance" <[EMAIL PROTECTED]> 3/28/01 8:34:49 AM >>> >John, did you ever try distributing route for 8.0.0.0 instead of >0.0.0.0 >to see whether it was true for all routes or just the clammy "normal", >"default" default route :) ? _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: OSPF overrides "no ip classless"
I think you're right! All DRAM and no flashor is that the other way around? Maybe I'm all DRAM and no NVRAM, that's more like it. > >Now that I think about it, I believe I did try 10.0.0.0/8 and it still > >behaved classfully, even running OSPF. I'll try it again to make sure, > >though. I'm only 30 and my memory is already failing me. > > > >John > > I'll bet your memory isn't from a Cisco-approved supplier. See what happens? > > > > "Bob Vance" <[EMAIL PROTECTED]> 3/28/01 8:34:49 AM >>> > >John, did you ever try distributing route for 8.0.0.0 instead of > >0.0.0.0 > >to see whether it was true for all routes or just the clammy "normal", > >"default" default route :) ? > > _ > FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] ___ Send a cool gift with your E-Card http://www.bluemountain.com/giftcenter/ _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
UPDATE: OSPF overriding 'no ip classless'
Okay, here are my latest findings. Bob and others wanted me to try various supernet routes to see how the routers reacted. Well, I did, and the router with 'no ip classless' is definitely behaving classlessly when OSPF is running. First, a recap. I have router A connected to router B and am running OSPF. Router A is originating a default route, and Router B has 'no ip classless' configured. The prefix for the link is 10.1.1.0/24. By all official explanations of 'no ip classless', in this scenario if I tried to ping an unknown subnet of 10.0.0.0/8, it would fail and debugging would show that the packets were unroutable. This is true when I used RIP v1, RIP v2, IGRP, and EIGRP. However, when I use OSPF it's a whole 'nuther story! It shouldn't matter how the routes are installed, but for some reason, Router B behaves as if 'ip classless' were configured if I run OSPF. Tonight, I first tried the original experiment and originated 0.0.0.0/0. Router B behaved classlessly and would route packets for ANY destination to Router A. Next, I tried redistributing the static route for 10.0.0.0/8. Packets for any subnet of 10.0.0.0/8 would be routed, all other destinations would fail. Again, classless behavior. Thirdly, I redistributed a route for 8.0.0.0/5 just for grins. Packets destined for anything in that range were routed (8.0.0.0/8 throught 11.0.0.0/8) but all other unknown subnets failed. Ah!! I've tried this on two different routers and three different IOS versions and I get the same results. Where is it written that when OSPF is running that the router will now behave classlessly in spite of 'no ip classless' being in the configuration? I guess I have no problem with this, I just wish they would document it somewhere. If someone would like to try these tests to verify the results I'd appreciate it. I'd love to get some verification so I know I'm not just losing my mind. Thanks! John ___ Send a cool gift with your E-Card http://www.bluemountain.com/giftcenter/ _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
The Finale: OSPF and IP Classless
If you thought this behavior was odd before, this will really bake your noodle. I did some more experiments as we discussed in the thread earlier today. Here's another short recap to catch everyone up. I have two routers, A and B, running OSPF. The link between them is 10.1.1.0/24, and A is originating a default into B. Router B has 'no ip classless' configured. This means that by Cisco's explanations, if I were to ping any unknown subnet of 10.0.0.0/8 it would fail and debugging would show that it was unroutable. However, that wasn't happening. If I used OSPF to originate a 0.0.0.0/0 default route, it would be installed as GOLR and router B would behave classlessly. I tried this using 0.0.0.0/0, 10.0.0.0/8, and 8.0.0.0/5. In all cases, when using OSPF to originate the route, router B would behave classlessly. This behavior would not occur when I used RIP v1 or v2, IGRP, or EIGRP. (If I understood IS-IS, I'd try that too.) Tonight I changed tactics and tried some new things. First, I ran two routing protocols, OSPF and RIP, but I let RIP advertise the default 0.0.0.0/0 to B. As expected, B behaved classfully and would not use the supernet route. This shows us that it's not merely the presence of OSPF on a router that can cause it to override 'no ip classless'. Next, I configured a manual static default 0.0.0.0/0 route on B while Router A was also advertising the same route. Of course the OSPF route would not be installed into the table because of the higher AD, but I wanted to verify Router B's behavior. In this case, it was classfull. Next, I set the AD of the static route to 120, higher than the 110 AD of the OSPF route. This means that the new GOLR, even thought it looks *exactly* the same in the routing table, was installed by OSPF. Guess what? Yep, classless behavior! Now for the really interesting part (if you've read this far and are still awake!) I set a static 0.0.0.0/0 route on Router B but then also advertised 10.1.0.0/16 from router A. Now Router B behaved classlessly but only for subnets of 10.1.0.0/16! If I tried to ping 10.2.1.1, for instance, it was unroutable, but any subnet of 10.1.0.0/16--even the unknown ones--would be routed based on the OSPF-installed supernet route. I then added 10.2.0.0/16 to the advertisement and saw what I expected: packets destined for either of those two subnets would be routed, all others failed. This means that the router behaves classlessly if there is a supernet route that was installed by OSPF...but only up to that point! In the situation I just mentioned, remember that there was also a static default route that was being ignored! So, the new rule is this: a router with 'no ip classless' configured will not forward traffic to unknown subnets of known major networks UNLESS THERE IS A VALID SUPERNET ROUTE INSTALLED BY OSPF. (sorry for the caps. ) Yikes, can this thread die now? :-) I know, I keep it going, but I wanted to really chase this down. I think I chased it down, kicked it, hit it with a stick, and now it's gone belly up not unlike the Norwegian Blue. As for me, I think I'm through with my 'no ip classless' experiments. Now maybe I can finally get to those NAT labs I've been trying to get to for a week! Regards, John ___ Send a cool gift with your E-Card http://www.bluemountain.com/giftcenter/ _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: no ip classless [7:7100]
If you were running RIP V1 on your network, correct design would dictate that all the local networks "must" appear in the routing table of your routers. If one of your users accesses a network not in the table, the router would send an icmp "network unreachable" with no IP classless and an icmp "timeout" error (after a long wait) with ip classless. This behavior prevents some routing loops, prevents traffic to nonexistant devices and is good design. Doug Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=7136&t=7100 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: no ip classless [7:7100]
Cisco routers by default are still classfull, even though the internet has long since gone classless. For a router to effective understand CIDR routes that don't fall on classfull boundrys it is necessary to turn off the default by executing the command ip classless If for some reason you live in a time warp, and your network is fully classfull, and you just got a used router from someone who was using it on a classless network, and you wanted to convert it back to being classfull you would execute the command no ip classless. Why Classless? Lets say you have a large network, and you happen to own a class A network. Lets say the 5.0.0.0 network. Lets say that one of the interfaces on your router connects to another router which connects to your larger network. Let say that on your end the interface address is 5.0.0.1 /30 and on the other end the address is 5.0.0.2 /30. Lets say you have a default route pointing out the serial interface that has the 5.0.0.1 interface. If you then tried to reach something else in the 5.0.0.0 network, say 5.1.2.3, the packet would go to your router. (remember our router is configured for classfull, the default). Then your router would say to itself "hey I have an interface in the 5 network, that means that all of 5.0.0.0 /8 must be connected to me, but I don't see the specific network I'm trying to reach (5.1.2.3) sop I guess it doesn't exist so I'll throw the packet away" That's what happens if your router is set to classful SO to recap Classfull cisco default BAD Classless need ip classless command GOOD hope this helps Tom At 12:31 PM 06/04/2001 -0400, [EMAIL PROTECTED] wrote: >In what situation would you use the command "no ip classless"? > >Cisco's site says >ip classless --- This command allows the software to forward packets that are >destined for unrecognized subnets of directly connected networks. The packets >are forwarded to the best supernet route. > >no ip classless --- When this feature is disabled, the software discards the >packets when a router receives packets for a subnet that numerically falls >within its subnetwork addressing scheme, if there is no such subnet number in >the routing table and there is no network default route. > >When would you use this in the real world? Tom Pruneau Trainer Network Operations GENUITY 3 Van de Graff Drive Burlington Ma. 01803 24 Hr. Network Operations Center 800-436-8489 If you need to get a hold of me my hours are 8AM-4PM ET Mon-Fri --- This email is composed of 82% post consumer recycled data bits --- "Once in a while you get shown the light in the strangest of places if you look at it right" Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=7139&t=7100 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: no ip classless [7:7100]
Tom; I think a discussion on this will be interesting. My perseption is that a classful/classless router has nothing to do with VLSM or CIDR. The only issue is how it handles the default route on networks that are attached to the router with at least one interface. Classless - attached net, subnet not in table, forward to DG. Classful - attached net, subnet not in table, drop and generate ICMP to host. Doug Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=7155&t=7100 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: no ip classless [7:7100]
Search the archives for 2-3 iterations of the discussion culminating with Chuck doing some heavy lab work. Peter *** REPLY SEPARATOR *** On 6/4/2001 at 5:15 PM Doug Lockwood wrote: >Tom; > >I think a discussion on this will be interesting. >My perseption is that a classful/classless router >has nothing to do with VLSM or CIDR. > >The only issue is how it handles the default route >on networks that are attached to the router with at least one interface. > >Classless - attached net, subnet not in table, forward to DG. >Classful - attached net, subnet not in table, drop and generate ICMP to >host. > >Doug Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=7164&t=7100 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: IP classless command [7:30056]
The best way to explain IP classless is to explain how a router works with "no ip classless". Suppose you have a router with a static route configured to 10.1.1.0/24 out some interface and you also have a default gateway configured. Again, ip classless is disabled, "no ip classless". A packet comes into the router destined for 10.1.1.2, the router looks at the routing table, sees the static route and forwards as expected. A packet comes into the router destined for 11.x.x.x, the router looks at the routing table, sees the default gateway and forwards as expected. A packet comes into the router destined for 10.10.10.1, you would expect the router to forward the packet via the default gateway. However, because the router is operting in "classful mode", the router drops the packet rather then using the default gateway. This is because the router is in the same classful network as the 10.1.1.0/24 network used for the static route. If the "ip classless" command was used, the dropped packet would actually be forwarded via the default gateway. There really is no reason not to use "ip classless" on all router configurations. Mike ""Hunt Lee"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Can anyone please explain to me what is "ip classless" used for? I looked > it up on the Caslow book, and it states that by enabling IP classless, it > allows one to override the contiguous subnet rule and allow the router to > look for the longest match beyond the listed subnets. > > But I still don't understand what it means? Can anyone give me some > examples? > > Thanks in advance. > > Best Regards, > Hunt Lee > IP Solution Analyst > Cable & Wireless Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=30058&t=30056 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: IP classless command [7:30056]
12/24/2001 5:35pm Monday Well said - Original Message - From: ""Mike"" Newsgroups: groupstudy.cisco Sent: Monday, December 24, 2001 5:35 PM Subject: Re: IP classless command [7:30056] > The best way to explain IP classless is to explain how a router works with > "no ip classless". Suppose you have a router with a static route configured > to 10.1.1.0/24 out some interface and you also have a default gateway > configured. Again, ip classless is disabled, "no ip classless". > > A packet comes into the router destined for 10.1.1.2, the router looks at > the routing table, sees the static route and forwards as expected. > > A packet comes into the router destined for 11.x.x.x, the router looks at > the routing table, sees the default gateway and forwards as expected. > > A packet comes into the router destined for 10.10.10.1, you would expect the > router to forward the packet via the default gateway. However, because the > router is operting in "classful mode", the router drops the packet rather > then using the default gateway. This is because the router is in the same > classful network as the 10.1.1.0/24 network used for the static route. > > If the "ip classless" command was used, the dropped packet would actually be > forwarded via the default gateway. There really is no reason not to use "ip > classless" on all router configurations. > > Mike > > > > ""Hunt Lee"" wrote in message > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > Can anyone please explain to me what is "ip classless" used for? I looked > > it up on the Caslow book, and it states that by enabling IP classless, it > > allows one to override the contiguous subnet rule and allow the router to > > look for the longest match beyond the listed subnets. > > > > But I still don't understand what it means? Can anyone give me some > > examples? > > > > Thanks in advance. > > > > Best Regards, > > Hunt Lee > > IP Solution Analyst > > Cable & Wireless Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=30063&t=30056 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: IP classless command [7:30056]
IP CLASSLESS is a little hard to understand. Even Cisco is very vague on this. Once a TAC engineer just told me that the command just makes routing better. Here is what I believe happens. If you don't have the "IP CLASSLESS" command defined in a Cisco router then the router will not forward any packets towards a default route for any subnets of a classfull network that the router thinks are local. For instance. Rtr A local net 10.1.0.0/24. 192.168.1.0 interconnects routers a and b RTR B (sends default network only to RTR A and RTR C) 192.168.2.0 interconnects routers b and C RTR C local net 10.2.0.0/24 Note how 10.0.0.0 is split by the 192.168.1.0 and 192.168.2.0 networks. In the above example if RTR A gets a packet destined for 10.2.0.1, but it does not have the "IP CLASSLESS" command defined then RTR A will drop the packets. If you include the IP CLASSLESS command then the packets will be forwarded to the default router b. I hope this helps Mike Paulson Network Architect Infrastructure Design Systems LLP Hunt Lee wrote: > Can anyone please explain to me what is "ip classless" used for? I looked > it up on the Caslow book, and it states that by enabling IP classless, it > allows one to override the contiguous subnet rule and allow the router to > look for the longest match beyond the listed subnets. > > But I still don't understand what it means? Can anyone give me some > examples? > > Thanks in advance. > > Best Regards, > Hunt Lee > IP Solution Analyst > Cable & Wireless [GroupStudy.com removed an attachment of type text/x-vcard which had a name of michael.paulson.vcf] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=30087&t=30056 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: IP classless command [7:30056]
Hello Mike. thanks so much for your detailed explanation. However, I'm still confused about how the ip classless works. I understand that "classful" rules (if no ip classless is configured), with the 10.1.1.0/24 static route, it would forward anything from 10.1.1.1 to 10.1.1.254, but why would it worked for 11.x.x.x? Also, with the "ip classless", will it just forward anything like 10.x.x.x? Thanks again. Hunt ""Mike"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > The best way to explain IP classless is to explain how a router works with > "no ip classless". Suppose you have a router with a static route configured > to 10.1.1.0/24 out some interface and you also have a default gateway > configured. Again, ip classless is disabled, "no ip classless". > > A packet comes into the router destined for 10.1.1.2, the router looks at > the routing table, sees the static route and forwards as expected. > > A packet comes into the router destined for 11.x.x.x, the router looks at > the routing table, sees the default gateway and forwards as expected. > > A packet comes into the router destined for 10.10.10.1, you would expect the > router to forward the packet via the default gateway. However, because the > router is operting in "classful mode", the router drops the packet rather > then using the default gateway. This is because the router is in the same > classful network as the 10.1.1.0/24 network used for the static route. > > If the "ip classless" command was used, the dropped packet would actually be > forwarded via the default gateway. There really is no reason not to use "ip > classless" on all router configurations. > > Mike > > > > ""Hunt Lee"" wrote in message > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > Can anyone please explain to me what is "ip classless" used for? I looked > > it up on the Caslow book, and it states that by enabling IP classless, it > > allows one to override the contiguous subnet rule and allow the router to > > look for the longest match beyond the listed subnets. > > > > But I still don't understand what it means? Can anyone give me some > > examples? > > > > Thanks in advance. > > > > Best Regards, > > Hunt Lee > > IP Solution Analyst > > Cable & Wireless Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=30089&t=30056 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: IP classless command [7:30056]
Hunt, With "no ip classless" configured, the router assumes classful behavior. If it has any route at all to a network it assumes that it has routing to all of that major network (this is why RIP has such problems with discontiginous networks). If it receives a packet destined for a major network for which it has routing but for a subnet that it does not have a route to it presumes that there is no route available to the subnet and black holes it. If a classful router receives a packet for a major network that it does not have a route to, it sensibly forwards it to the default route. This type of behavior only makes sense from the point of view of a classful routing protocol (RIP, IGRP, etc) where there is an underlying presumption of knowledge of an entire major network if the router has any routes to that major network. "No ip classless" can cause some very weird behavior and should be configured in modern networks only very cautiously. Dave -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Hunt Lee Sent: Tuesday, December 25, 2001 5:45 PM To: [EMAIL PROTECTED] Subject: Re: IP classless command [7:30056] Hello Mike. thanks so much for your detailed explanation. However, I'm still confused about how the ip classless works. I understand that "classful" rules (if no ip classless is configured), with the 10.1.1.0/24 static route, it would forward anything from 10.1.1.1 to 10.1.1.254, but why would it worked for 11.x.x.x? Also, with the "ip classless", will it just forward anything like 10.x.x.x? Thanks again. Hunt ""Mike"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > The best way to explain IP classless is to explain how a router works with > "no ip classless". Suppose you have a router with a static route configured > to 10.1.1.0/24 out some interface and you also have a default gateway > configured. Again, ip classless is disabled, "no ip classless". > > A packet comes into the router destined for 10.1.1.2, the router looks at > the routing table, sees the static route and forwards as expected. > > A packet comes into the router destined for 11.x.x.x, the router looks at > the routing table, sees the default gateway and forwards as expected. > > A packet comes into the router destined for 10.10.10.1, you would expect the > router to forward the packet via the default gateway. However, because the > router is operting in "classful mode", the router drops the packet rather > then using the default gateway. This is because the router is in the same > classful network as the 10.1.1.0/24 network used for the static route. > > If the "ip classless" command was used, the dropped packet would actually be > forwarded via the default gateway. There really is no reason not to use "ip > classless" on all router configurations. > > Mike > > > > ""Hunt Lee"" wrote in message > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > Can anyone please explain to me what is "ip classless" used for? I looked > > it up on the Caslow book, and it states that by enabling IP classless, it > > allows one to override the contiguous subnet rule and allow the router to > > look for the longest match beyond the listed subnets. > > > > But I still don't understand what it means? Can anyone give me some > > examples? > > > > Thanks in advance. > > > > Best Regards, > > Hunt Lee > > IP Solution Analyst > > Cable & Wireless Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=30090&t=30056 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: IP classless command [7:30056]
For a simple explanation if IP classless, see: http://www.networkking.net/out/ipclassless.htm Bernard > -Original Message- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] > Sent: Tuesday, December 25, 2001 12:41 PM > To: [EMAIL PROTECTED] > Subject: Re: IP classless command [7:30056] > > IP CLASSLESS is a little hard to understand. Even Cisco is very vague on > this. Once a > TAC engineer just told me that the command just makes routing better. > Here > is what I > believe happens. > > If you don't have the "IP CLASSLESS" command defined in a Cisco router > then > the router > will not forward any packets towards a default route for any subnets of a > classfull > network that the router thinks are local. For instance. > > Rtr A local net 10.1.0.0/24. > 192.168.1.0 interconnects routers a and b > RTR B (sends default network only to RTR A and RTR C) > 192.168.2.0 interconnects routers b and C > RTR C local net 10.2.0.0/24 > Note how 10.0.0.0 is split by the 192.168.1.0 and 192.168.2.0 networks. > > In the above example if RTR A gets a packet destined for 10.2.0.1, but it > does not have > the "IP CLASSLESS" command defined then RTR A will drop the packets. > > If you include the IP CLASSLESS command then the packets will be forwarded > to the > default router b. > > I hope this helps > Mike Paulson > Network Architect > Infrastructure Design Systems LLP > > > Hunt Lee wrote: > > > Can anyone please explain to me what is "ip classless" used for? I > looked > > it up on the Caslow book, and it states that by enabling IP classless, > it > > allows one to override the contiguous subnet rule and allow the router > to > > look for the longest match beyond the listed subnets. > > > > But I still don't understand what it means? Can anyone give me some > > examples? > > > > Thanks in advance. > > > > Best Regards, > > Hunt Lee > > IP Solution Analyst > > Cable & Wireless > > [GroupStudy.com removed an attachment of type text/x-vcard which had a > name > of michael.paulson.vcf] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=30093&t=30056 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: IP classless command [7:30056]
Brilliant! Pierre-Alex -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Bernard Omrani Sent: Tuesday, December 25, 2001 7:21 PM To: [EMAIL PROTECTED] Subject: RE: IP classless command [7:30056] For a simple explanation if IP classless, see: http://www.networkking.net/out/ipclassless.htm Bernard > -Original Message- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] > Sent: Tuesday, December 25, 2001 12:41 PM > To: [EMAIL PROTECTED] > Subject: Re: IP classless command [7:30056] > > IP CLASSLESS is a little hard to understand. Even Cisco is very vague on > this. Once a > TAC engineer just told me that the command just makes routing better. > Here > is what I > believe happens. > > If you don't have the "IP CLASSLESS" command defined in a Cisco router > then > the router > will not forward any packets towards a default route for any subnets of a > classfull > network that the router thinks are local. For instance. > > Rtr A local net 10.1.0.0/24. > 192.168.1.0 interconnects routers a and b > RTR B (sends default network only to RTR A and RTR C) > 192.168.2.0 interconnects routers b and C > RTR C local net 10.2.0.0/24 > Note how 10.0.0.0 is split by the 192.168.1.0 and 192.168.2.0 networks. > > In the above example if RTR A gets a packet destined for 10.2.0.1, but it > does not have > the "IP CLASSLESS" command defined then RTR A will drop the packets. > > If you include the IP CLASSLESS command then the packets will be forwarded > to the > default router b. > > I hope this helps > Mike Paulson > Network Architect > Infrastructure Design Systems LLP > > > Hunt Lee wrote: > > > Can anyone please explain to me what is "ip classless" used for? I > looked > > it up on the Caslow book, and it states that by enabling IP classless, > it > > allows one to override the contiguous subnet rule and allow the router > to > > look for the longest match beyond the listed subnets. > > > > But I still don't understand what it means? Can anyone give me some > > examples? > > > > Thanks in advance. > > > > Best Regards, > > Hunt Lee > > IP Solution Analyst > > Cable & Wireless > > [GroupStudy.com removed an attachment of type text/x-vcard which had a > name > of michael.paulson.vcf] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=30097&t=30056 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: IP classless command [7:30056]
The history is like this: In the beginning it used to be that a classful IP address block (such as 170.15.0.0 /16 or 197.100.2.0 /24) was assigned to a particular organization for its exclusive use. If that organization chose to subnet that block, and the organization's routers did not have a route listed for a particular subnet of that block, then a packet for that block would be dropped (even if a gateway of last resort had been configured). The logic being that if your organization doesn't know where that subnet is then nobody does, and thus the packet is dropped. These days, ISPs have possession of various address blocks which they divvy up as needed to their customers. So its absolutely common for the various subnets of a particular classful address block to be split up amongst multiple organizations. So the ip classless command was used to get around this default behavior of the router. Recognizing the changed landscape of IP address allocation, ip classless became part of a router's default configuration starting with IOS version 11.3, permitting packets for any destination not explicitly listed in the router's routing table to utilize the router's configured gateway of last resort. Official information: http://www.cisco.com/univercd/cc/td/doc/product/software/ios120/12cgcr/np1_r /1rprt2/1ripadr.htm#1018036 Dan Garfield CCNP, CCDP, CCSI, MCSE, CNE, CTT, A+ 221 Oak Springs Drive San Anselmo, CA 94960 phone: (415) 453-5659 fax: (413) 691-6074 ""[EMAIL PROTECTED]"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Brilliant! > > Pierre-Alex > > -Original Message- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of > Bernard Omrani > Sent: Tuesday, December 25, 2001 7:21 PM > To: [EMAIL PROTECTED] > Subject: RE: IP classless command [7:30056] > > > For a simple explanation if IP classless, see: > > http://www.networkking.net/out/ipclassless.htm > > > Bernard > > > > -Original Message- > > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] > > Sent: Tuesday, December 25, 2001 12:41 PM > > To: [EMAIL PROTECTED] > > Subject: Re: IP classless command [7:30056] > > > > IP CLASSLESS is a little hard to understand. Even Cisco is very vague > on > > this. Once a > > TAC engineer just told me that the command just makes routing better. > > Here > > is what I > > believe happens. > > > > If you don't have the "IP CLASSLESS" command defined in a Cisco > router > > then > > the router > > will not forward any packets towards a default route for any subnets > of a > > classfull > > network that the router thinks are local. For instance. > > > > Rtr A local net 10.1.0.0/24. > > 192.168.1.0 interconnects routers a and b > > RTR B (sends default network only to RTR A and RTR C) > > 192.168.2.0 interconnects routers b and C > > RTR C local net 10.2.0.0/24 > > Note how 10.0.0.0 is split by the 192.168.1.0 and 192.168.2.0 > networks. > > > > In the above example if RTR A gets a packet destined for 10.2.0.1, but > it > > does not have > > the "IP CLASSLESS" command defined then RTR A will drop the packets. > > > > If you include the IP CLASSLESS command then the packets will be > forwarded > > to the > > default router b. > > > > I hope this helps > > Mike Paulson > > Network Architect > > Infrastructure Design Systems LLP > > > > > > Hunt Lee wrote: > > > > > Can anyone please explain to me what is "ip classless" used for? I > > looked > > > it up on the Caslow book, and it states that by enabling IP > classless, > > it > > > allows one to override the contiguous subnet rule and allow the > router > > to > > > look for the longest match beyond the listed subnets. > > > > > > But I still don't understand what it means? Can anyone give me some > > > examples? > > > > > > Thanks in advance. > > > > > > Best Regards, > > > Hunt Lee > > > IP Solution Analyst > > > Cable & Wireless > > > > [GroupStudy.com removed an attachment of type text/x-vcard which had a > > name > > of michael.paulson.vcf] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=30122&t=30056 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
IP Classless Revisited (this is just odd...)
Ok, just when you thought it was safe to go back in the water Or should I say, just when I thought I understood the behavior of 'ip classess' and 'no ip classless' Let me summarize my lab setup. RouterA-RouterB--RouterC Pretty simple. AtoB is 10.1.1.0/24, BtoA is 10.1.2.0/24. OSPF is running on both links. 'ip classless' is on A and C, but not B initially. On B I see these routes: 10.0.0.0/24 is subnetted, 2 subnets C 10.1.2.0 is directly connected, Serial1 C 10.1.1.0 is directly connected, Serial0 That's what I expect to see. Then I add a default route on B, 'ip route 0.0.0.0 0.0.0.0 10.1.1.2'. With no ip classless configured, any packets to unknown subnets of 10.0.0.0/8 should be dropped. I tested it and that is the case. With 'ip classless' configured, and unknown packets regardless of major network get routed to 10.1.1.2. Now here is what I don't understand. Let's turn off ip classless on B again, then go to Router C and add a default route to null0 and default-information originate to the ospf process. I now see this in router B: 10.0.0.0/24 is subnetted, 2 subnets C 10.1.2.0 is directly connected, Serial1 C 10.1.1.0 is directly connected, Serial0 O*E2 0.0.0.0/0 [110/1] via 10.1.2.2, 00:06:38, Serial1 There is indeed a default route. With no ip classless configured, I would expect the same behavior as before. If I were to ping 10.5.5.5 the packets should be unroutable, but they're not! They get routed to the default route whether or not ip classless is configured. Why is a default route learned through a routing protocol treated differently than a manually configured default route? I went through this entire process twice and I just don't understand the behavior. What am I missing? I know it's going to be something obvious, but I don't see it yet. Ok, I just now tried this: with the ospf external default route still in the routing table, I pinged 10.5.5.5 and it took the default route. Then I manually added a default static route and the destination became unroutable due to 'no ip classless' being configured. Removing the static default it becomes routable again. Weird. What's going on? Thanks, John ___ Send a cool gift with your E-Card http://www.bluemountain.com/giftcenter/ _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: More Info (OSPF and IP Classless)
Using different type area with differnet option redistribute default route, still the same result? Would like to hear the result? rgds; Vincent "John Neiberger" <[EMAIL PROTECTED]> ¼¶¼g©ó¶l¥ó [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Here is a link verifying that my understanding of 'no ip classless' is > correct! > > http://www.cisco.com/warp/public/105/21.html > > So, referring to my other threads, why is OSPF overriding classfull routing > table lookups? I'd rather not retype the whole thing, so if you'd like the > details of my experiments, refer to the other threads. I just wanted to > post this link to show that I wasn't entirely crazy! Maybe a little, but > not entirely. > > Regards, > John the Not-entirely Insane (formerly John the Cheerful, PKA John the > Monday Grump) > > > > > > ___ > Send a cool gift with your E-Card > http://www.bluemountain.com/giftcenter/ > > > _ > FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: More Info (OSPF and IP Classless)
"ip classless" or "no ip classless" only affect the way the router lookup the ip route table. It does not related to how you define the ospf area or how you redistribute the route (inc the default route). ""wind"" <[EMAIL PROTECTED]> wrote in message 99s3lo$8v1$[EMAIL PROTECTED]">news:99s3lo$8v1$[EMAIL PROTECTED]... > Using different type area with differnet option redistribute default route, > still the same result? > > Would like to hear the result? > > rgds; > Vincent > > "John Neiberger" <[EMAIL PROTECTED]> ¼¶¼g©ó¶l¥ó > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > Here is a link verifying that my understanding of 'no ip classless' is > > correct! > > > > http://www.cisco.com/warp/public/105/21.html > > > > So, referring to my other threads, why is OSPF overriding classfull > routing > > table lookups? I'd rather not retype the whole thing, so if you'd like > the > > details of my experiments, refer to the other threads. I just wanted to > > post this link to show that I wasn't entirely crazy! Maybe a little, but > > not entirely. > > > > Regards, > > John the Not-entirely Insane (formerly John the Cheerful, PKA John the > > Monday Grump) > > > > > > > > > > > > ___ > > Send a cool gift with your E-Card > > http://www.bluemountain.com/giftcenter/ > > > > > > _ > > FAQ, list archives, and subscription info: > http://www.groupstudy.com/list/cisco.html > > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > > > > _ > FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: More Info (OSPF and IP Classless)
Just want to see the result by using different type of area. By using ospf routing protocol with no ip classless, the route distribute from the other router behave ip classless. PS. Did you read the other thread ""Katson PN Yeung"" <[EMAIL PROTECTED]> ¼¶¼g©ó¶l¥ó 99s52g$bp9$[EMAIL PROTECTED]">news:99s52g$bp9$[EMAIL PROTECTED]... > "ip classless" or "no ip classless" only affect the way the router lookup > the ip route table. It does not related to how you define the ospf area or > how you redistribute the route (inc the default route). > > > ""wind"" <[EMAIL PROTECTED]> wrote in message > 99s3lo$8v1$[EMAIL PROTECTED]">news:99s3lo$8v1$[EMAIL PROTECTED]... > > Using different type area with differnet option redistribute default > route, > > still the same result? > > > > Would like to hear the result? > > > > rgds; > > Vincent > > > > "John Neiberger" <[EMAIL PROTECTED]> ¼¶¼g©ó¶l¥ó > > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > Here is a link verifying that my understanding of 'no ip classless' is > > > correct! > > > > > > http://www.cisco.com/warp/public/105/21.html > > > > > > So, referring to my other threads, why is OSPF overriding classfull > > routing > > > table lookups? I'd rather not retype the whole thing, so if you'd like > > the > > > details of my experiments, refer to the other threads. I just wanted to > > > post this link to show that I wasn't entirely crazy! Maybe a little, > but > > > not entirely. > > > > > > Regards, > > > John the Not-entirely Insane (formerly John the Cheerful, PKA John the > > > Monday Grump) > > > > > > > > > > > > > > > > > > ___ > > > Send a cool gift with your E-Card > > > http://www.bluemountain.com/giftcenter/ > > > > > > > > > _ > > > FAQ, list archives, and subscription info: > > http://www.groupstudy.com/list/cisco.html > > > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > > > > > > > > _ > > FAQ, list archives, and subscription info: > http://www.groupstudy.com/list/cisco.html > > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > > > > _ > FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: More Info (OSPF and IP Classless)
When I did my original testing, both routers were in area 0. When I get home tonight I'll try putting the default-advertising router into a different area just for grins. I'll also try changing the default advertisement to a type 1 external instead of type 2. I have no idea why that would have an effect here, but who knows... John > Just want to see the result by using different type of area. > > By using ospf routing protocol with no ip classless, the route distribute > from the other > router behave ip classless. > > PS. Did you read the other thread > > ""Katson PN Yeung"" <[EMAIL PROTECTED]> ¼¶¼g©ó¶l¥ó > 99s52g$bp9$[EMAIL PROTECTED]">news:99s52g$bp9$[EMAIL PROTECTED]... > > "ip classless" or "no ip classless" only affect the way the router lookup > > the ip route table. It does not related to how you define the ospf area or > > how you redistribute the route (inc the default route). > > > > > > ""wind"" <[EMAIL PROTECTED]> wrote in message > > 99s3lo$8v1$[EMAIL PROTECTED]">news:99s3lo$8v1$[EMAIL PROTECTED]... > > > Using different type area with differnet option redistribute default > > route, > > > still the same result? > > > > > > Would like to hear the result? > > > > > > rgds; > > > Vincent > > > > > > "John Neiberger" <[EMAIL PROTECTED]> ¼¶¼g©ó¶l¥ó > > > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > > Here is a link verifying that my understanding of 'no ip classless' is > > > > correct! > > > > > > > > http://www.cisco.com/warp/public/105/21.html > > > > > > > > So, referring to my other threads, why is OSPF overriding classfull > > > routing > > > > table lookups? I'd rather not retype the whole thing, so if you'd > like > > > the > > > > details of my experiments, refer to the other threads. I just wanted > to > > > > post this link to show that I wasn't entirely crazy! Maybe a little, > > but > > > > not entirely. > > > > > > > > Regards, > > > > John the Not-entirely Insane (formerly John the Cheerful, PKA John the > > > > Monday Grump) > > > > > > > > > > > > > > > > > > > > > > > > ___ > > > > Send a cool gift with your E-Card > > > > http://www.bluemountain.com/giftcenter/ > > > > > > > > > > > > _ > > > > FAQ, list archives, and subscription info: > > > http://www.groupstudy.com/list/cisco.html > > > > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > > > > > > > > > > > > _ > > > FAQ, list archives, and subscription info: > > http://www.groupstudy.com/list/cisco.html > > > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > > > > > > > > _ > > FAQ, list archives, and subscription info: > http://www.groupstudy.com/list/cisco.html > > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > > > > _ > FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] ___ Send a cool gift with your E-Card http://www.bluemountain.com/giftcenter/ _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: UPDATE: OSPF overriding 'no ip classless'
Interesting :) And, of course, if it were a designed feature, it should be documented. Someone should call this in. - Tks | <mailto:[EMAIL PROTECTED]> BV | <mailto:[EMAIL PROTECTED]> Sr. Technical Consultant, SBM, A Gates/Arrow Co. Vox 770-623-3430 11455 Lakefield Dr. Fax 770-623-3429 Duluth, GA 30097-1511 = -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of John Neiberger Sent: Thursday, March 29, 2001 12:23 AM To: [EMAIL PROTECTED] Subject: UPDATE: OSPF overriding 'no ip classless' Okay, here are my latest findings. Bob and others wanted me to try various supernet routes to see how the routers reacted. Well, I did, and the router with 'no ip classless' is definitely behaving classlessly when OSPF is running. First, a recap. I have router A connected to router B and am running OSPF. Router A is originating a default route, and Router B has 'no ip classless' configured. The prefix for the link is 10.1.1.0/24. By all official explanations of 'no ip classless', in this scenario if I tried to ping an unknown subnet of 10.0.0.0/8, it would fail and debugging would show that the packets were unroutable. This is true when I used RIP v1, RIP v2, IGRP, and EIGRP. However, when I use OSPF it's a whole 'nuther story! It shouldn't matter how the routes are installed, but for some reason, Router B behaves as if 'ip classless' were configured if I run OSPF. Tonight, I first tried the original experiment and originated 0.0.0.0/0. Router B behaved classlessly and would route packets for ANY destination to Router A. Next, I tried redistributing the static route for 10.0.0.0/8. Packets for any subnet of 10.0.0.0/8 would be routed, all other destinations would fail. Again, classless behavior. Thirdly, I redistributed a route for 8.0.0.0/5 just for grins. Packets destined for anything in that range were routed (8.0.0.0/8 throught 11.0.0.0/8) but all other unknown subnets failed. Ah!! I've tried this on two different routers and three different IOS versions and I get the same results. Where is it written that when OSPF is running that the router will now behave classlessly in spite of 'no ip classless' being in the configuration? I guess I have no problem with this, I just wish they would document it somewhere. If someone would like to try these tests to verify the results I'd appreciate it. I'd love to get some verification so I know I'm not just losing my mind. Thanks! John ___ Send a cool gift with your E-Card http://www.bluemountain.com/giftcenter/ _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: The Finale: OSPF and IP Classless
Hi John, I would like to add another point to your observation. With 'no ip classless' , EIGRP also behaves the same way as OSPF when you have a supernet for the specific major net. > Now for the really interesting part (if you've read this far and are still > awake!) I set a static 0.0.0.0/0 route on Router B but then also advertised > 10.1.0.0/16 from router A. Now Router B behaved classlessly but only for > subnets of 10.1.0.0/16! If I tried to ping 10.2.1.1, for instance, it was > unroutable, but any subnet of 10.1.0.0/16--even the unknown ones--would be > routed based on the OSPF-installed supernet route. I then added 10.2.0.0/16 > to the advertisement and saw what I expected: packets destined for either > of those two subnets would be routed, all others failed. It works the same way if you repeat the above with EIGRP. But, the default route or GOLR is not considered under this situation if it is installed by EIGRP, whereas it is looked up when we use OSPF. Looks like 'ip classless' command is closely tied with the default route, rather than generically relating to a supernet. Regards, Srikanth. - Original Message - From: John Neiberger <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Friday, March 30, 2001 5:09 AM Subject: The Finale: OSPF and IP Classless > If you thought this behavior was odd before, this will really bake your > noodle. I did some more experiments as we discussed in the thread earlier > today. Here's another short recap to catch everyone up. > > I have two routers, A and B, running OSPF. The link between them is > 10.1.1.0/24, and A is originating a default into B. Router B has 'no ip > classless' configured. This means that by Cisco's explanations, if I were > to ping any unknown subnet of 10.0.0.0/8 it would fail and debugging would > show that it was unroutable. However, that wasn't happening. If I used > OSPF to originate a 0.0.0.0/0 default route, it would be installed as GOLR > and router B would behave classlessly. > > I tried this using 0.0.0.0/0, 10.0.0.0/8, and 8.0.0.0/5. In all cases, when > using OSPF to originate the route, router B would behave classlessly. This > behavior would not occur when I used RIP v1 or v2, IGRP, or EIGRP. (If I > understood IS-IS, I'd try that too.) > > Tonight I changed tactics and tried some new things. First, I ran two > routing protocols, OSPF and RIP, but I let RIP advertise the default > 0.0.0.0/0 to B. As expected, B behaved classfully and would not use the > supernet route. This shows us that it's not merely the presence of OSPF on > a router that can cause it to override 'no ip classless'. > > Next, I configured a manual static default 0.0.0.0/0 route on B while Router > A was also advertising the same route. Of course the OSPF route would not > be installed into the table because of the higher AD, but I wanted to verify > Router B's behavior. In this case, it was classfull. > > Next, I set the AD of the static route to 120, higher than the 110 AD of the > OSPF route. This means that the new GOLR, even thought it looks *exactly* > the same in the routing table, was installed by OSPF. Guess what? Yep, > classless behavior! > > Now for the really interesting part (if you've read this far and are still > awake!) I set a static 0.0.0.0/0 route on Router B but then also advertised > 10.1.0.0/16 from router A. Now Router B behaved classlessly but only for > subnets of 10.1.0.0/16! If I tried to ping 10.2.1.1, for instance, it was > unroutable, but any subnet of 10.1.0.0/16--even the unknown ones--would be > routed based on the OSPF-installed supernet route. I then added 10.2.0.0/16 > to the advertisement and saw what I expected: packets destined for either > of those two subnets would be routed, all others failed. > > This means that the router behaves classlessly if there is a supernet route > that was installed by OSPF...but only up to that point! In the situation I > just mentioned, remember that there was also a static default route that was > being ignored! > > So, the new rule is this: a router with 'no ip classless' configured will > not forward traffic to unknown subnets of known major networks UNLESS THERE > IS A VALID SUPERNET ROUTE INSTALLED BY OSPF. (sorry for the caps. ) > > Yikes, can this thread die now? :-) I know, I keep it going, but I wanted > to really chase this down. I think I chased it down, kicked it, hit it with > a stick, and now it's gone belly up not unlike the Norwegian Blue. As for > me, I think I'm through with my 'no ip classless' experiments. Now maybe I > can finally get to those NAT labs I've been trying to get to for a wee
Re: The Finale: OSPF and IP Classless
In my testing, I found exactly the opposite, which is why all of this is so odd. With 'no ip classless' configured and using EIGRP to originate a default from Router A into Router B, B would still behave classfully in its route lookups. It would *not* use a supernet route for destinations in unknown subnets of known major networks. (geez, what a mouthfull!). Specifically in my case, the link is 10.1.1.0/24. When router A would advertise a 0.0.0.0/0 route to router B and I tried to ping 10.5.5.5, for instance, it would fail, as expected. The router knows about 10.1.1.0/24 but it doesn't know anything about 10.5.5.5. In classfull operation, that is unroutable. Now if I remove EIGRP and use OSPF for this, router B starts to behave classlessly in its lookups even if 'no ip classless' is still configured! That is the true oddity here. I've seen no documentation that says OSPF overrides 'no ip classless' but that is, in fact, what I've proven to my satisfaction. I've tried just about every possible configuration I (and a few others) could think of and I can predict consistently how it's going to behave now. If anyone would like to see a VERY long detailed description of the experiments including configurations and command output, I could put it together. I'd rather you do it yourselves on your own equipment, though, to verify these results. Besides, that's a lot of work. Regards, John >>> "R.Srikanth" <[EMAIL PROTECTED]> 3/30/01 9:17:28 AM >>> Hi John, I would like to add another point to your observation. With 'no ip classless' , EIGRP also behaves the same way as OSPF when you have a supernet for the specific major net. > Now for the really interesting part (if you've read this far and are still > awake!) I set a static 0.0.0.0/0 route on Router B but then also advertised > 10.1.0.0/16 from router A. Now Router B behaved classlessly but only for > subnets of 10.1.0.0/16! If I tried to ping 10.2.1.1, for instance, it was > unroutable, but any subnet of 10.1.0.0/16--even the unknown ones--would be > routed based on the OSPF-installed supernet route. I then added 10.2.0.0/16 > to the advertisement and saw what I expected: packets destined for either > of those two subnets would be routed, all others failed. It works the same way if you repeat the above with EIGRP. But, the default route or GOLR is not considered under this situation if it is installed by EIGRP, whereas it is looked up when we use OSPF. Looks like 'ip classless' command is closely tied with the default route, rather than generically relating to a supernet. Regards, Srikanth. - Original Message ----- From: John Neiberger <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Friday, March 30, 2001 5:09 AM Subject: The Finale: OSPF and IP Classless > If you thought this behavior was odd before, this will really bake your > noodle. I did some more experiments as we discussed in the thread earlier > today. Here's another short recap to catch everyone up. > > I have two routers, A and B, running OSPF. The link between them is > 10.1.1.0/24, and A is originating a default into B. Router B has 'no ip > classless' configured. This means that by Cisco's explanations, if I were > to ping any unknown subnet of 10.0.0.0/8 it would fail and debugging would > show that it was unroutable. However, that wasn't happening. If I used > OSPF to originate a 0.0.0.0/0 default route, it would be installed as GOLR > and router B would behave classlessly. > > I tried this using 0.0.0.0/0, 10.0.0.0/8, and 8.0.0.0/5. In all cases, when > using OSPF to originate the route, router B would behave classlessly. This > behavior would not occur when I used RIP v1 or v2, IGRP, or EIGRP. (If I > understood IS-IS, I'd try that too.) > > Tonight I changed tactics and tried some new things. First, I ran two > routing protocols, OSPF and RIP, but I let RIP advertise the default > 0.0.0.0/0 to B. As expected, B behaved classfully and would not use the > supernet route. This shows us that it's not merely the presence of OSPF on > a router that can cause it to override 'no ip classless'. > > Next, I configured a manual static default 0.0.0.0/0 route on B while Router > A was also advertising the same route. Of course the OSPF route would not > be installed into the table because of the higher AD, but I wanted to verify > Router B's behavior. In this case, it was classfull. > > Next, I set the AD of the static route to 120, higher than the 110 AD of the > OSPF route. This means that the new GOLR, even thought it looks *exactly* > the same in the routing table, was installed by OSPF. Guess what? Yep, > classless behavior! > > Now for
ip classless and default route [7:53231]
according to many books, ip classless should be used to be able to use default route. but I just found my internet router, actually has no ip classless. which means I am using classful route lookup. And this is working fine,who can explain why note that ip address here is not real one. ! hostname xxx ! enable secret xxx ! ip subnet-zero no ip domain-lookup ip name-server x.x.x.x ! interface FastEthernet0/0 ip address 210.210.210.62 255.255.255.240 no ip directed-broadcast ! interface Serial0/0 bandwidth 64 ip unnumbered FastEthernet0/0 no ip directed-broadcast no ip mroute-cache no fair-queue ! no ip classless ip route 0.0.0.0 0.0.0.0 Serial0/0 Gateway of last resort is 0.0.0.0 to network 0.0.0.0 210.210.210.0/28 is subnetted, 1 subnets C 210.210.210.48 is directly connected, FastEthernet0/0 S* 0.0.0.0/0 is directly connected, Serial0/0 xxx# xxx#sh flash System flash directory: File Length Name/status 1 3612344 c2600-i-mz.120-3.T3 [3612408 bytes used, 4776200 available, 8388608 total] 8192K bytes of processor board System flash (Read/Write) Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=53231&t=53231 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
IP Classless (from Q&A Forum at Cisco)
I got this off teh Q&A forum, and thought the group would enjoy reading it... Question: What is the function of command ip classless in such a network OSPF is used as the routing protocol. Would it be possible to explain it by giving an example? Answer: The ip classless command makes the router consider IP classless, so that it will not consider IP addresses to be of class A, B, and so on. So, it enables IP addresses like 198.108.10.1 255.255.0.0. Also, when using classful protocols like IGRP or RIP, it makes a routing decision based on its classless nature. It is used only if you have the gateway of last resort set and it determines whether or not you forward traffic to the component of the major net that is not in your forwarding table. For example, your major network is 10.0.0.0 and subnetted with a prefix of 24 bit. Let's say that you have packets going to 10.10.10.0 and that entry is not in your forwarding table. If you have no ip classless the packet is dropped whether or not you have a gateway of last resort. If you have classless on, the default route is used. **NOTE: New CCNA/CCDA List has been formed. For more information go to http://www.groupstudy.com/list/Associates.html _ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: IP Classless Revisited (this is just odd...)
John, Interesting. I think this is due to OSPF, not redistribution problem. Can you try running RIP instead of OSPF ? Cheers, YY -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of John Neiberger Sent: Sunday, March 25, 2001 5:28 AM To: [EMAIL PROTECTED] Subject: IP Classless Revisited (this is just odd...) Ok, just when you thought it was safe to go back in the water Or should I say, just when I thought I understood the behavior of 'ip classess' and 'no ip classless' Let me summarize my lab setup. RouterA-RouterB--RouterC Pretty simple. AtoB is 10.1.1.0/24, BtoA is 10.1.2.0/24. OSPF is running on both links. 'ip classless' is on A and C, but not B initially. On B I see these routes: 10.0.0.0/24 is subnetted, 2 subnets C 10.1.2.0 is directly connected, Serial1 C 10.1.1.0 is directly connected, Serial0 That's what I expect to see. Then I add a default route on B, 'ip route 0.0.0.0 0.0.0.0 10.1.1.2'. With no ip classless configured, any packets to unknown subnets of 10.0.0.0/8 should be dropped. I tested it and that is the case. With 'ip classless' configured, and unknown packets regardless of major network get routed to 10.1.1.2. Now here is what I don't understand. Let's turn off ip classless on B again, then go to Router C and add a default route to null0 and default-information originate to the ospf process. I now see this in router B: 10.0.0.0/24 is subnetted, 2 subnets C 10.1.2.0 is directly connected, Serial1 C 10.1.1.0 is directly connected, Serial0 O*E2 0.0.0.0/0 [110/1] via 10.1.2.2, 00:06:38, Serial1 There is indeed a default route. With no ip classless configured, I would expect the same behavior as before. If I were to ping 10.5.5.5 the packets should be unroutable, but they're not! They get routed to the default route whether or not ip classless is configured. Why is a default route learned through a routing protocol treated differently than a manually configured default route? I went through this entire process twice and I just don't understand the behavior. What am I missing? I know it's going to be something obvious, but I don't see it yet. Ok, I just now tried this: with the ospf external default route still in the routing table, I pinged 10.5.5.5 and it took the default route. Then I manually added a default static route and the destination became unroutable due to 'no ip classless' being configured. Removing the static default it becomes routable again. Weird. What's going on? Thanks, John ___ Send a cool gift with your E-Card http://www.bluemountain.com/giftcenter/ _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: IP Classless Revisited (this is just odd...)
Sure, I'll try that but I don't see why it should matter. As I understand it, ip classless affects routing table lookups only and it doesn't care how those routes were installed into the table. Although, given this behavior, my assumption might be wrong. Thanks, John > John, > Interesting. I think this is due to OSPF, not redistribution problem. Can you try running RIP instead of OSPF ? > > Cheers, > YY > > > > -Original Message- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of > John Neiberger > Sent: Sunday, March 25, 2001 5:28 AM > To: [EMAIL PROTECTED] > Subject: IP Classless Revisited (this is just odd...) > > > Ok, just when you thought it was safe to go back in the water Or should > I say, just when I thought I understood the behavior of 'ip classess' and > 'no ip classless' Let me summarize my lab setup. > > RouterA-RouterB--RouterC > > Pretty simple. AtoB is 10.1.1.0/24, BtoA is 10.1.2.0/24. OSPF is running > on both links. 'ip classless' is on A and C, but not B initially. On B I > see these routes: > > 10.0.0.0/24 is subnetted, 2 subnets > C 10.1.2.0 is directly connected, Serial1 > C 10.1.1.0 is directly connected, Serial0 > > That's what I expect to see. Then I add a default route on B, 'ip route > 0.0.0.0 0.0.0.0 10.1.1.2'. With no ip classless configured, any packets to > unknown subnets of 10.0.0.0/8 should be dropped. I tested it and that is > the case. With 'ip classless' configured, and unknown packets regardless of > major network get routed to 10.1.1.2. > > Now here is what I don't understand. Let's turn off ip classless on B > again, then go to Router C and add a default route to null0 and > default-information originate to the ospf process. I now see this in router > B: > > 10.0.0.0/24 is subnetted, 2 subnets > C 10.1.2.0 is directly connected, Serial1 > C 10.1.1.0 is directly connected, Serial0 > O*E2 0.0.0.0/0 [110/1] via 10.1.2.2, 00:06:38, Serial1 > > There is indeed a default route. With no ip classless configured, I would > expect the same behavior as before. If I were to ping 10.5.5.5 the packets > should be unroutable, but they're not! They get routed to the default route > whether or not ip classless is configured. > > Why is a default route learned through a routing protocol treated > differently than a manually configured default route? I went through this > entire process twice and I just don't understand the behavior. > > What am I missing? I know it's going to be something obvious, but I don't > see it yet. > > Ok, I just now tried this: with the ospf external default route still in > the routing table, I pinged 10.5.5.5 and it took the default route. Then I > manually added a default static route and the destination became unroutable > due to 'no ip classless' being configured. Removing the static default it > becomes routable again. > > Weird. What's going on? > > Thanks, > John > > > > > > ___ > Send a cool gift with your E-Card > http://www.bluemountain.com/giftcenter/ > > > _ > FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] ___ Send a cool gift with your E-Card http://www.bluemountain.com/giftcenter/ _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: IP Classless Revisited (this is just odd...)
I'm not sure how that helps in this case. In both scenarios, whether using RIP or OSPF, the default route is being learned dynamically by the hub router and it is installed into the routing table. The problem is that with no ip classless configured, that router should never use the default route when trying to reach unknown subnets of 10.x.x.x. When running RIP, it behaves as expected. When running OSPF, it behaves as if ip classless were configured. Any other thoughts? Thanks John <http://www.cisco.com/univercd/cc/td/doc/product/software/ios113ed/113ed_cr/np1_c/1cindep.htm#37279 -Mike>> ___ Send a cool gift with your E-Card http://www.bluemountain.com/giftcenter/ _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: IP Classless Revisited (this is just odd...)
Could this have been an issue with route summarization, where the pass-through router (C) had summaries from both sides (couldn't make a decision). If you disable classless on one router, the route & summary will be assigned in one direction & the true path to the second router will be defined. Phil - Original Message - From: "John Neiberger" <[EMAIL PROTECTED]> To: "YY" <[EMAIL PROTECTED]> Cc: <[EMAIL PROTECTED]> Sent: Sunday, March 25, 2001 3:01 PM Subject: RE: IP Classless Revisited (this is just odd...) > Sure, I'll try that but I don't see why it should matter. As I understand > it, ip classless affects routing table lookups only and it doesn't care how > those routes were installed into the table. > > Although, given this behavior, my assumption might be wrong. > > Thanks, > John > > > John, > > Interesting. I think this is due to OSPF, not redistribution problem. > Can you try running RIP instead of OSPF ? > > > > Cheers, > > YY > > > > > > > > -Original Message- > > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of > > John Neiberger > > Sent: Sunday, March 25, 2001 5:28 AM > > To: [EMAIL PROTECTED] > > Subject: IP Classless Revisited (this is just odd...) > > > > > > Ok, just when you thought it was safe to go back in the water Or > should > > I say, just when I thought I understood the behavior of 'ip classess' and > > 'no ip classless' Let me summarize my lab setup. > > > > RouterA-RouterB--RouterC > > > > Pretty simple. AtoB is 10.1.1.0/24, BtoA is 10.1.2.0/24. OSPF is > running > > on both links. 'ip classless' is on A and C, but not B initially. On B > I > > see these routes: > > > > 10.0.0.0/24 is subnetted, 2 subnets > > C 10.1.2.0 is directly connected, Serial1 > > C 10.1.1.0 is directly connected, Serial0 > > > > That's what I expect to see. Then I add a default route on B, 'ip route > > 0.0.0.0 0.0.0.0 10.1.1.2'. With no ip classless configured, any packets > to > > unknown subnets of 10.0.0.0/8 should be dropped. I tested it and that is > > the case. With 'ip classless' configured, and unknown packets regardless > of > > major network get routed to 10.1.1.2. > > > > Now here is what I don't understand. Let's turn off ip classless on B > > again, then go to Router C and add a default route to null0 and > > default-information originate to the ospf process. I now see this in > router > > B: > > > > 10.0.0.0/24 is subnetted, 2 subnets > > C 10.1.2.0 is directly connected, Serial1 > > C 10.1.1.0 is directly connected, Serial0 > > O*E2 0.0.0.0/0 [110/1] via 10.1.2.2, 00:06:38, Serial1 > > > > There is indeed a default route. With no ip classless configured, I > would > > expect the same behavior as before. If I were to ping 10.5.5.5 the > packets > > should be unroutable, but they're not! They get routed to the default > route > > whether or not ip classless is configured. > > > > Why is a default route learned through a routing protocol treated > > differently than a manually configured default route? I went through > this > > entire process twice and I just don't understand the behavior. > > > > What am I missing? I know it's going to be something obvious, but I > don't > > see it yet. > > > > Ok, I just now tried this: with the ospf external default route still in > > the routing table, I pinged 10.5.5.5 and it took the default route. Then > I > > manually added a default static route and the destination became > unroutable > > due to 'no ip classless' being configured. Removing the static default > it > > becomes routable again. > > > > Weird. What's going on? > > > > Thanks, > > John > > > > > > > > > > > > ___ > > Send a cool gift with your E-Card > > http://www.bluemountain.com/giftcenter/ > > > > > > _ > > FAQ, list archives, and subscription info: > http://www.groupstudy.com/list/cisco.html > > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > > > > > ___ > Send a cool gift with your E-Card > http://www.bluemountain.com/giftcenter/ > > > _ > FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: IP Classless Revisited (this is just odd...)
Not that its at all helpful in this situation, but ip classless, much like bgp synchronization, fall into the category of commands that simply defy understanding when presented with test criteria. One must keep in mind that these are implementations of code that sometimes are not 100% reflective of what the designer intended. On the other hand, just when you think the code is flawed, you find out that you truly misunderstood the feature in the first place :) The end result is generally frustration or increased understanding, or sometimes both in that order. Pete *** REPLY SEPARATOR *** On 3/25/2001 at 10:38 AM John Neiberger wrote: >I'm not sure how that helps in this case. In both scenarios, whether >using >RIP or OSPF, the default route is being learned dynamically by the hub >router and it is installed into the routing table. The problem is that >with >no ip classless configured, that router should never use the default route >when trying to reach unknown subnets of 10.x.x.x. When running RIP, it >behaves as expected. When running OSPF, it behaves as if ip classless were >configured. > >Any other thoughts? > >Thanks >John > >< >John >Take a look at the Cisco link below, for a sanity >check.http://www.cisco.com/univercd/cc/td/doc/product/software/ios113ed/113ed_cr/np1_c/1cindep.htm#37279 > >-Mike>> > > > > > >___ >Send a cool gift with your E-Card >http://www.bluemountain.com/giftcenter/ > > >_ >FAQ, list archives, and subscription info: >http://www.groupstudy.com/list/cisco.html >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: IP Classless Revisited (this is just odd...)
Heh heh...yes, ip classless and bgp synchronization do fit into that category quite well! I am starting to think this is an IOS feature on this router. I tried this with RIP, EIGRP, and OSPF. 'no ip classless' behaved exactly as expected when running RIP and EIGRP. It was only when I used OSPF that it started to behave classlessly without my prior authorization. I've got a 2501 running a different IOS image. I think I'll try this experiment on that to see what happens. Thanks, John > Not that its at all helpful in this situation, but ip classless, much like bgp synchronization, fall into the category of commands that simply defy understanding when presented with test criteria. One must keep in mind that these are implementations of code that sometimes are not 100% reflective of what the designer intended. On the other hand, just when you think the code is flawed, you find out that you truly misunderstood the feature in the first place :) > > The end result is generally frustration or increased understanding, or sometimes both in that order. > > Pete > > > *** REPLY SEPARATOR *** > > On 3/25/2001 at 10:38 AM John Neiberger wrote: > > >I'm not sure how that helps in this case. In both scenarios, whether > >using > >RIP or OSPF, the default route is being learned dynamically by the hub > >router and it is installed into the routing table. The problem is that > >with > >no ip classless configured, that router should never use the default route > >when trying to reach unknown subnets of 10.x.x.x. When running RIP, it > >behaves as expected. When running OSPF, it behaves as if ip classless were > >configured. > > > >Any other thoughts? > > > >Thanks > >John > > > >< > > >John > >Take a look at the Cisco link below, for a sanity > >check.http://www.cisco.com/univercd/cc/td/doc/product/software/ios113ed/113ed_cr/np1_c/1cindep.htm#37279 > > > >-Mike>> > > > > > > > > > > > >___ > >Send a cool gift with your E-Card > >http://www.bluemountain.com/giftcenter/ > > > > > >_ > >FAQ, list archives, and subscription info: > >http://www.groupstudy.com/list/cisco.html > >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > > ___ Send a cool gift with your E-Card http://www.bluemountain.com/giftcenter/ _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: FW: UPDATE: OSPF overriding 'no ip classless'
Well, there are two different issues. You're talking about the way the routing protocols themselves behave: whether they pass subnet mask information or not. The issue here is routing table lookups, not how those routes are installed. With 'no ip classless' configured, even if there is a valid supernet route in the routing table--including a 0.0.0.0/0 default route--the router should not choose it. For some reason, at least on my routers, if OSPF is running it changes this behavior. This is pretty odd. To be consistent Cisco should cause the configuration to change to 'ip classless' when an OSPF process is configured. Hey, here's something I didn't try! Someone should do this during the day since I won't be able to do it until tonight. Run OSPF *and* another routing protocol, let's say RIP, but use RIP to advertise the default route, not OSPF. That would be an interesting test to see if the router is behaving classlessly only for OSPF-learned routes or if it really makes the router become completely classless. Okay, I need to get started on my coffee. John >>> "Stull, Cory" <[EMAIL PROTECTED]> 3/29/01 7:50:04 AM >>> John, I haven't followed this as closely as I should have before answering but I hope I am guessing correctly here... OSPF sends the subnet information along with it when it does its routing updates, the only way to have it behave classfully is to manually summarize. The reason the other protocols were working the way they were is because they either A) don't send subnet information in the updates or B) were autosummarizing at the classful network boundary like EIGRP does. Am I way off base here? I'm working on an OSPF type lab right now too so let me know. Cory -Original Message- From: Bob Vance [mailto:[EMAIL PROTECTED]] Sent: Thursday, March 29, 2001 8:22 AM To: CISCO_GroupStudy List (E-mail) Subject: RE: UPDATE: OSPF overriding 'no ip classless' Interesting :) And, of course, if it were a designed feature, it should be documented. Someone should call this in. - Tks| <mailto:[EMAIL PROTECTED]> BV | <mailto:[EMAIL PROTECTED]> Sr. Technical Consultant, SBM, A Gates/Arrow Co. Vox 770-623-3430 11455 Lakefield Dr. Fax 770-623-3429 Duluth, GA 30097-1511 = -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of John Neiberger Sent: Thursday, March 29, 2001 12:23 AM To: [EMAIL PROTECTED] Subject: UPDATE: OSPF overriding 'no ip classless' Okay, here are my latest findings. Bob and others wanted me to try various supernet routes to see how the routers reacted. Well, I did, and the router with 'no ip classless' is definitely behaving classlessly when OSPF is running. First, a recap. I have router A connected to router B and am running OSPF. Router A is originating a default route, and Router B has 'no ip classless' configured. The prefix for the link is 10.1.1.0/24. By all official explanations of 'no ip classless', in this scenario if I tried to ping an unknown subnet of 10.0.0.0/8, it would fail and debugging would show that the packets were unroutable. This is true when I used RIP v1, RIP v2, IGRP, and EIGRP. However, when I use OSPF it's a whole 'nuther story! It shouldn't matter how the routes are installed, but for some reason, Router B behaves as if 'ip classless' were configured if I run OSPF. Tonight, I first tried the original experiment and originated 0.0.0.0/0. Router B behaved classlessly and would route packets for ANY destination to Router A. Next, I tried redistributing the static route for 10.0.0.0/8. Packets for any subnet of 10.0.0.0/8 would be routed, all other destinations would fail. Again, classless behavior. Thirdly, I redistributed a route for 8.0.0.0/5 just for grins. Packets destined for anything in that range were routed (8.0.0.0/8 throught 11.0.0.0/8) but all other unknown subnets failed. Ah!! I've tried this on two different routers and three different IOS versions and I get the same results. Where is it written that when OSPF is running that the router will now behave classlessly in spite of 'no ip classless' being in the configuration? I guess I have no problem with this, I just wish they would document it somewhere. If someone would like to try these tests to verify the results I'd appreciate it. I'd love to get some verification so I know I'm not just losing my mind. Thanks! John ___ Send a cool gift with your E-Card http://www.bluemountain.com/giftcenter/ _ FAQ, list archives, and subscription info: http://www.groupstudy.com/li
RE: FW: UPDATE: OSPF overriding 'no ip classless'
Excellent !! This is like the Energizer Bunny! Hmmm. You already tested adding a static default route (with lower admin distance) and it changed the classless behavior, right? Then you deleted the static and classless returned. Just for completeness :) , it might be mildly interesting to add the static with a higher admin than OSPF -- it won't show up in the routing table and thus it shouldn't change the classless behavior like the lower admin one did -- or would it ;>) Also, allow OSPF also to advertise the default, along with RIP, and see that since the OSPF route is in the table, it still subverts to classless even though it knows that it also received a RIP route that it is currently ignoring. - Tks | <mailto:[EMAIL PROTECTED]> BV | <mailto:[EMAIL PROTECTED]> Sr. Technical Consultant, SBM, A Gates/Arrow Co. Vox 770-623-3430 11455 Lakefield Dr. Fax 770-623-3429 Duluth, GA 30097-1511 = -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of John Neiberger Sent: Thursday, March 29, 2001 10:16 AM To: [EMAIL PROTECTED] Cc: [EMAIL PROTECTED] Subject: Re: FW: UPDATE: OSPF overriding 'no ip classless' Well, there are two different issues. You're talking about the way the routing protocols themselves behave: whether they pass subnet mask information or not. The issue here is routing table lookups, not how those routes are installed. With 'no ip classless' configured, even if there is a valid supernet route in the routing table--including a 0.0.0.0/0 default route--the router should not choose it. For some reason, at least on my routers, if OSPF is running it changes this behavior. This is pretty odd. To be consistent Cisco should cause the configuration to change to 'ip classless' when an OSPF process is configured. Hey, here's something I didn't try! Someone should do this during the day since I won't be able to do it until tonight. Run OSPF *and* another routing protocol, let's say RIP, but use RIP to advertise the default route, not OSPF. That would be an interesting test to see if the router is behaving classlessly only for OSPF-learned routes or if it really makes the router become completely classless. Okay, I need to get started on my coffee. John >>> "Stull, Cory" <[EMAIL PROTECTED]> 3/29/01 7:50:04 AM >>> John, I haven't followed this as closely as I should have before answering but I hope I am guessing correctly here... OSPF sends the subnet information along with it when it does its routing updates, the only way to have it behave classfully is to manually summarize. The reason the other protocols were working the way they were is because they either A) don't send subnet information in the updates or B) were autosummarizing at the classful network boundary like EIGRP does. Am I way off base here? I'm working on an OSPF type lab right now too so let me know. Cory -Original Message- From: Bob Vance [mailto:[EMAIL PROTECTED]] Sent: Thursday, March 29, 2001 8:22 AM To: CISCO_GroupStudy List (E-mail) Subject: RE: UPDATE: OSPF overriding 'no ip classless' Interesting :) And, of course, if it were a designed feature, it should be documented. Someone should call this in. - Tks| <mailto:[EMAIL PROTECTED]> BV | <mailto:[EMAIL PROTECTED]> Sr. Technical Consultant, SBM, A Gates/Arrow Co. Vox 770-623-3430 11455 Lakefield Dr. Fax 770-623-3429 Duluth, GA 30097-1511 = -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of John Neiberger Sent: Thursday, March 29, 2001 12:23 AM To: [EMAIL PROTECTED] Subject: UPDATE: OSPF overriding 'no ip classless' Okay, here are my latest findings. Bob and others wanted me to try various supernet routes to see how the routers reacted. Well, I did, and the router with 'no ip classless' is definitely behaving classlessly when OSPF is running. First, a recap. I have router A connected to router B and am running OSPF. Router A is originating a default route, and Router B has 'no ip classless' configured. The prefix for the link is 10.1.1.0/24. By all official explanations of 'no ip classless', in this scenario if I tried to ping an unknown subnet of 10.0.0.0/8, it would fail and debugging would show that the packets were unroutable. This is true when I used RIP v1, RIP v2, IGRP, and EIGRP. However, when I use OSPF it's a whole 'nuther story! It shouldn't matter how the routes are installed, but for some reason, Router B behaves as if 'ip classless' were configured if I run OSPF. Toni
RE: FW: UPDATE: OSPF overriding 'no ip classless'
One thing I didn't try, which you might be alluding to, is allowing OSPF to advertise the default (which was causing classless behavior) but then also manually add a static default on router B. I have not tried that yet. I did try the manual static default route without OSPF advertising the default and the router behaved classfully. Then, as you suggest, I could change the distance on the manually added default to see what happens. So, there are two more things to try right there. You're right Bob, this just keeps going and going and going I just want to hear someone from Cisco say "Whoops, didn't we tell you about that? Sorry, forgot...we'll go document that feature now." Either that or I want to find out I've been missing something this whole time. Certainly I can't be the first person to notice this, especially since I've tried this with older IOS versions. >>> "Bob Vance" <[EMAIL PROTECTED]> 3/29/01 9:53:36 AM >>> Excellent !! This is like the Energizer Bunny! Hmmm. You already tested adding a static default route (with lower admin distance) and it changed the classless behavior, right? Then you deleted the static and classless returned. Just for completeness :) , it might be mildly interesting to add the static with a higher admin than OSPF -- it won't show up in the routing table and thus it shouldn't change the classless behavior like the lower admin one did -- or would it ;>) Also, allow OSPF also to advertise the default, along with RIP, and see that since the OSPF route is in the table, it still subverts to classless even though it knows that it also received a RIP route that it is currently ignoring. - Tks| <mailto:[EMAIL PROTECTED]> BV | <mailto:[EMAIL PROTECTED]> Sr. Technical Consultant, SBM, A Gates/Arrow Co. Vox 770-623-3430 11455 Lakefield Dr. Fax 770-623-3429 Duluth, GA 30097-1511 = -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of John Neiberger Sent: Thursday, March 29, 2001 10:16 AM To: [EMAIL PROTECTED] Cc: [EMAIL PROTECTED] Subject: Re: FW: UPDATE: OSPF overriding 'no ip classless' Well, there are two different issues. You're talking about the way the routing protocols themselves behave: whether they pass subnet mask information or not. The issue here is routing table lookups, not how those routes are installed. With 'no ip classless' configured, even if there is a valid supernet route in the routing table--including a 0.0.0.0/0 default route--the router should not choose it. For some reason, at least on my routers, if OSPF is running it changes this behavior. This is pretty odd. To be consistent Cisco should cause the configuration to change to 'ip classless' when an OSPF process is configured. Hey, here's something I didn't try! Someone should do this during the day since I won't be able to do it until tonight. Run OSPF *and* another routing protocol, let's say RIP, but use RIP to advertise the default route, not OSPF. That would be an interesting test to see if the router is behaving classlessly only for OSPF-learned routes or if it really makes the router become completely classless. Okay, I need to get started on my coffee. John >>> "Stull, Cory" <[EMAIL PROTECTED]> 3/29/01 7:50:04 AM >>> John, I haven't followed this as closely as I should have before answering but I hope I am guessing correctly here... OSPF sends the subnet information along with it when it does its routing updates, the only way to have it behave classfully is to manually summarize. The reason the other protocols were working the way they were is because they either A) don't send subnet information in the updates or B) were autosummarizing at the classful network boundary like EIGRP does. Am I way off base here? I'm working on an OSPF type lab right now too so let me know. Cory -Original Message- From: Bob Vance [mailto:[EMAIL PROTECTED]] Sent: Thursday, March 29, 2001 8:22 AM To: CISCO_GroupStudy List (E-mail) Subject: RE: UPDATE: OSPF overriding 'no ip classless' Interesting :) And, of course, if it were a designed feature, it should be documented. Someone should call this in. - Tks| <mailto:[EMAIL PROTECTED]> BV | <mailto:[EMAIL PROTECTED]> Sr. Technical Consultant, SBM, A Gates/Arrow Co. Vox 770-623-3430 11455 Lakefield Dr. Fax 770-623-3429 Duluth, GA 30097-1511 ========= -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of John Neiberger Sent: Thursday, March 29, 2001 12:23 A
ANSWER: OSPF overrides 'no ip classless' [7:1758]
I have received results from a TAC case about this familiar issue. For those coming late to the picnic, the issue was that the presence of OSPF or IS-IS overrides 'no ip classless' in the router configuration and would force the router to behave classlessly. The TAC engineer consulted with some Development Engineers and here is what they said: Yes, we do this if the default (or the supernet) route is supplied by OSPF or ISIS (I guess EIGRP should be there, but it is not) and the part of the code that requested the RT lookup didn't not specify to ignore the default route if there's no specific subnet (which is the case for the locally originated and transit packets). The assumption is that it is safe to use a default/supernet route installed by a classless protocol. So what ever you and me have seen in our testing is correct behaviour. So, our original guesses were correct. The router assumes that if we're running OSPF or IS-IS then we want classless routing even if we didn't specify 'ip classless' in the config. However, an important point is that this applies only if the supernet was installed by the classless protocol. If OSPF or IS-IS is running on a router but the supernet was installed by another process, then classful routing would still apply without the addition of 'ip classless' to the config. I've also discovered that if you add 'ip clueless' to the config, the following occurs: First, ip classless is overridden but only in cases where no ip classless was manually configured previously and was not the default setting, unless the router has not had any previous configuration and is running at least 12.1(5F)T12. This does not apply for any 12.0 images except 12.0(6)S but does apply to any 11.2 image after 11.2(26c)P; Second, the gateway of last resort might be chosen by the RT lookup process if the GOLR was set by a classless routing protocol with an administrative distance lower than that of any other classless or classful routing protocol on the router, except in the case of BGP or EGP in which case the administrative distance must be at least equal to that of the routing protocol which previously installed the GOLR, if already present; Thirdly, if the lowest-weighted routing protocol is OSPF and the GOLR is advertised to neighbor as an E2 route, then the neighbor router may choose to use that route unless another neighbor has advertised the same supernet route as an E1 route. In which case--but especially when utilizing IP over Avian Carriers (with QoS)--the RT lookup will choose the Type 1 External route unless EIGRP is running on this router as well. In that case, the GOLR will be set via EIGRP because Cisco prefers EIGRP to OSPF and we should all use that anyway because, don't ya know, OSPF is harder to configure and requires way too much thought to begin with. IS-IS is just out of the question. However, if a router learns a supernet route via OSPF and IS-IS *and* EIGRP then you will be severely punished. Flogging is generally suggested. As an alternative, only run EIGRP and leave "ip clueless" configured. Any other configuration will provide ambiguous results. HTH, John Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=1758&t=1758 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: ip classless and default route [7:53231]
You don't need the "ip classless" command because your default route points to an unnumbered serial interface. If instead it pointed to an IP address that was in the same class as your local Ethernet, then you would have a problem. Here's the classic example: e0 RouterA s0 -- s0 RouterB -->Internet routerA int e0 172.16.10.1 255.255.255.0 int s0 172.16.20.1 255.255.255.0 ip route 0.0.0.0 0.0.0.0 172.16.20.2 routerB int s0 172.16.20.2 255.255.255.0 That confuses Router A. Without "ip classless," it thinks 172.16.0.0/16 is local. But that causes it not to be able to forward traffic to 172.16.20.2, the router on the other end of the serial link that has access to the rest of the world. Try it in a lab, if you get a chance. You'll see that in this situation, you need "ip classless." Priscilla YI Zhou wrote: > > according to many books, ip classless should be used to be able > to use default route. > > but I just found my internet router, actually has no ip > classless. > > which means I am using classful route lookup. > > And this is working fine,who can explain why > > note that ip address here is not real one. > > ! > hostname xxx > ! > enable secret xxx > ! > ip subnet-zero > no ip domain-lookup > ip name-server x.x.x.x > > ! > interface FastEthernet0/0 > ip address 210.210.210.62 255.255.255.240 > no ip directed-broadcast > ! > interface Serial0/0 > bandwidth 64 > ip unnumbered FastEthernet0/0 > no ip directed-broadcast > no ip mroute-cache > no fair-queue > ! > no ip classless > ip route 0.0.0.0 0.0.0.0 Serial0/0 > > > Gateway of last resort is 0.0.0.0 to network 0.0.0.0 > > 210.210.210.0/28 is subnetted, 1 subnets > C 210.210.210.48 is directly connected, FastEthernet0/0 > S* 0.0.0.0/0 is directly connected, Serial0/0 > xxx# > > xxx#sh flash > > System flash directory: > File Length Name/status > 1 3612344 c2600-i-mz.120-3.T3 > [3612408 bytes used, 4776200 available, 8388608 total] > 8192K bytes of processor board System flash (Read/Write) Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=53235&t=53231 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: ip classless and default route [7:53231]
It will work fine for any destination other then 210.210.210.x/24 which is the classful network for your IP subnet. A better real-world internet example with no ip classless and internet connections would be, if you had a 64.x.x.x subnet on the serial and similar on LAN side. In this case, 64.0.0.0/8 is the classful range. There are many other customers that have a subnet in this classful range out there. With 'no ip classless' and a default route with nexthop of 64.x.x.x any traffic destined to a 64.x.x.x site would fail, but traffic to 210.x.x.x, 65.x.x.x, etc would work. Erick --- YI Zhou wrote: > according to many books, ip classless should be used > to be able to use > default route. > > but I just found my internet router, actually has no > ip classless. > > which means I am using classful route lookup. > > And this is working fine,who can explain why > > note that ip address here is not real one. > > ! > hostname xxx > ! > enable secret xxx > ! > ip subnet-zero > no ip domain-lookup > ip name-server x.x.x.x > > ! > interface FastEthernet0/0 > ip address 210.210.210.62 255.255.255.240 > no ip directed-broadcast > ! > interface Serial0/0 > bandwidth 64 > ip unnumbered FastEthernet0/0 > no ip directed-broadcast > no ip mroute-cache > no fair-queue > ! > no ip classless > ip route 0.0.0.0 0.0.0.0 Serial0/0 > > > Gateway of last resort is 0.0.0.0 to network 0.0.0.0 > > 210.210.210.0/28 is subnetted, 1 subnets > C 210.210.210.48 is directly connected, > FastEthernet0/0 > S* 0.0.0.0/0 is directly connected, Serial0/0 > xxx# > > xxx#sh flash > > System flash directory: > File Length Name/status > 1 3612344 c2600-i-mz.120-3.T3 > [3612408 bytes used, 4776200 available, 8388608 > total] > 8192K bytes of processor board System flash > (Read/Write) [EMAIL PROTECTED] __ Do you Yahoo!? Yahoo! News - Today's headlines http://news.yahoo.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=53238&t=53231 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: ip classless and default route [7:53231]
Hmm, Try removing your static 0.0.0.0 and you'll see why. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] Sent: Thursday, September 12, 2002 8:57 PM To: [EMAIL PROTECTED] Subject: ip classless and default route [7:53231] according to many books, ip classless should be used to be able to use default route. but I just found my internet router, actually has no ip classless. which means I am using classful route lookup. And this is working fine,who can explain why note that ip address here is not real one. ! hostname xxx ! enable secret xxx ! ip subnet-zero no ip domain-lookup ip name-server x.x.x.x ! interface FastEthernet0/0 ip address 210.210.210.62 255.255.255.240 no ip directed-broadcast ! interface Serial0/0 bandwidth 64 ip unnumbered FastEthernet0/0 no ip directed-broadcast no ip mroute-cache no fair-queue ! no ip classless ip route 0.0.0.0 0.0.0.0 Serial0/0 Gateway of last resort is 0.0.0.0 to network 0.0.0.0 210.210.210.0/28 is subnetted, 1 subnets C 210.210.210.48 is directly connected, FastEthernet0/0 S* 0.0.0.0/0 is directly connected, Serial0/0 xxx# xxx#sh flash System flash directory: File Length Name/status 1 3612344 c2600-i-mz.120-3.T3 [3612408 bytes used, 4776200 available, 8388608 total] 8192K bytes of processor board System flash (Read/Write) Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=53240&t=53231 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: IP Classless (from Q&A Forum at Cisco)
Akiddeledivydo -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of Cthulu, CCIE Candidate Sent: Wednesday, September 27, 2000 7:09 AM To: [EMAIL PROTECTED] Subject:IP Classless (from Q&A Forum at Cisco) I got this off teh Q&A forum, and thought the group would enjoy reading it... Question: What is the function of command ip classless in such a network OSPF is used as the routing protocol. Would it be possible to explain it by giving an example? Answer: The ip classless command makes the router consider IP classless, so that it will not consider IP addresses to be of class A, B, and so on. So, it enables IP addresses like 198.108.10.1 255.255.0.0. Also, when using classful protocols like IGRP or RIP, it makes a routing decision based on its classless nature. It is used only if you have the gateway of last resort set and it determines whether or not you forward traffic to the component of the major net that is not in your forwarding table. For example, your major network is 10.0.0.0 and subnetted with a prefix of 24 bit. Let's say that you have packets going to 10.10.10.0 and that entry is not in your forwarding table. If you have no ip classless the packet is dropped whether or not you have a gateway of last resort. If you have classless on, the default route is used. **NOTE: New CCNA/CCDA List has been formed. For more information go to http://www.groupstudy.com/list/Associates.html _ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] **NOTE: New CCNA/CCDA List has been formed. For more information go to http://www.groupstudy.com/list/Associates.html _ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: The Finale: OSPF and IP Classless (partial retraction)
Oops, I just re-read your post and see that you were talking about advertising a specific major net, not the 0.0.0.0/0 default. So, are you saying that if I use EIGRP and advertise 10.0.0.0/8 from router A to router B that I can then successfully route packets destined for 10.5.5.5, for instance? So, just as in my experiments, the router behaves classlessly up to a point. In this example, it would use the major network supernet route but still would not be able to use the 0.0.0.0/0 supernet, right? Good grief. I'm just going to leave 'ip classless' on all the time and not worry about it. Thanks, John >>> "R.Srikanth" <[EMAIL PROTECTED]> 3/30/01 9:17:28 AM >>> Hi John, I would like to add another point to your observation. With 'no ip classless' , EIGRP also behaves the same way as OSPF when you have a supernet for the specific major net. > Now for the really interesting part (if you've read this far and are still > awake!) I set a static 0.0.0.0/0 route on Router B but then also advertised > 10.1.0.0/16 from router A. Now Router B behaved classlessly but only for > subnets of 10.1.0.0/16! If I tried to ping 10.2.1.1, for instance, it was > unroutable, but any subnet of 10.1.0.0/16--even the unknown ones--would be > routed based on the OSPF-installed supernet route. I then added 10.2.0.0/16 > to the advertisement and saw what I expected: packets destined for either > of those two subnets would be routed, all others failed. It works the same way if you repeat the above with EIGRP. But, the default route or GOLR is not considered under this situation if it is installed by EIGRP, whereas it is looked up when we use OSPF. Looks like 'ip classless' command is closely tied with the default route, rather than generically relating to a supernet. Regards, Srikanth. - Original Message - From: John Neiberger <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Friday, March 30, 2001 5:09 AM Subject: The Finale: OSPF and IP Classless > If you thought this behavior was odd before, this will really bake your > noodle. I did some more experiments as we discussed in the thread earlier > today. Here's another short recap to catch everyone up. > > I have two routers, A and B, running OSPF. The link between them is > 10.1.1.0/24, and A is originating a default into B. Router B has 'no ip > classless' configured. This means that by Cisco's explanations, if I were > to ping any unknown subnet of 10.0.0.0/8 it would fail and debugging would > show that it was unroutable. However, that wasn't happening. If I used > OSPF to originate a 0.0.0.0/0 default route, it would be installed as GOLR > and router B would behave classlessly. > > I tried this using 0.0.0.0/0, 10.0.0.0/8, and 8.0.0.0/5. In all cases, when > using OSPF to originate the route, router B would behave classlessly. This > behavior would not occur when I used RIP v1 or v2, IGRP, or EIGRP. (If I > understood IS-IS, I'd try that too.) > > Tonight I changed tactics and tried some new things. First, I ran two > routing protocols, OSPF and RIP, but I let RIP advertise the default > 0.0.0.0/0 to B. As expected, B behaved classfully and would not use the > supernet route. This shows us that it's not merely the presence of OSPF on > a router that can cause it to override 'no ip classless'. > > Next, I configured a manual static default 0.0.0.0/0 route on B while Router > A was also advertising the same route. Of course the OSPF route would not > be installed into the table because of the higher AD, but I wanted to verify > Router B's behavior. In this case, it was classfull. > > Next, I set the AD of the static route to 120, higher than the 110 AD of the > OSPF route. This means that the new GOLR, even thought it looks *exactly* > the same in the routing table, was installed by OSPF. Guess what? Yep, > classless behavior! > > Now for the really interesting part (if you've read this far and are still > awake!) I set a static 0.0.0.0/0 route on Router B but then also advertised > 10.1.0.0/16 from router A. Now Router B behaved classlessly but only for > subnets of 10.1.0.0/16! If I tried to ping 10.2.1.1, for instance, it was > unroutable, but any subnet of 10.1.0.0/16--even the unknown ones--would be > routed based on the OSPF-installed supernet route. I then added 10.2.0.0/16 > to the advertisement and saw what I expected: packets destined for either > of those two subnets would be routed, all others failed. > > This means that the router behaves classlessly if there is a supernet route > that was installed by OSPF...but only up to that point! In the situation I > just mentioned, remember that there was also a static de
RE: The Finale: OSPF and IP Classless (partial retraction)
Actually, John my treatises :) on this subject a year ago showed this.
ip classless
*only* affects the lookups *outside* the classful aggregate. Any
supernet *within* the classful aggregate *will* be used, even with
no ip classless
set.
Thus, a learned route, 10.1.0.0/16 , will be used for address 10.1.1.1
, but not 10.2.2.2 .
(*if* I still understand what I wrote below ;>).
Here is part of my original work on the subject for those who are
feeling drowsy, but just can't nod off completely ;>)
Thanks to the lab of
Ding So
I was able to pound the last nail in the coffin of how
[no] ip classless
affects route lookups (the doco makes no mention of route installation,
so we would guess that it has no effect. Further investigation will be
required to confirm/debunk this).
I will do a little write up, here, that can be challenged by anyone with
a dash of temerity:
(Note that I've tried several times and I just can't seem to
find a clear, yet succinct way to describe this.
)
==
Under old, classful routing it was assumed that all local networks would
be subnets of one or a couple of classful networks and that all the
subnets of a particular classful network, say "X" (e.g., X=172.16.0.0),
would be "connected" to each other.
What this means is that, for each and every pair of subnets of classful
network "X", there would be an interconnecting path among 1 or more
routers, that could be traversed *entirely* on segments whose IP network
addresses are subnets of classful network "X".
If the above requirement does not obtain, i.e., if the network path
*must* include a subnet of a *different* classful network, say "Y", then
we call this situation
"a discontiguous network".
or "X has discontiguous subnets"
or "X has disconnected subnets"
.
Another assumption in this environment is that, if we (a router) know
about any particular subnet of "X", then we should know about *all*
subnets of "X" that actually exist; either by our having one or more
interfaces within a subnet of X, an admin giving us proper static
routes,
or by information received from a routing protocol.
With the above in mind, the router will not entertain a route to a
subnet of network "Y" that isn't a route to a network address *within*
network "Y" (it can be that actual network aggregate, itself; e.g., a
route to 172.16.0.0/16, in the above example) -- that would mean
discontiguity.
In particular, it will *not* consider the "default" route
0.0.0.0/0
for any address within classful Y, if it has information about at least
one subnet of Y.
In addition (and this is the one always left out of the textbooks), it
will not consider *any* *supernets* routes of Y. The 0.0.0.0/0 is just
a particular case of this rule (0.0.0.0/0 is always a supernet of
*every*
network address -- it contains *0* bits that do not match).
If you look at a
show ip route
you'll notice that the table is broken up into sections at *classful*
network boundaries, *even* if
ip classless
is set.
Note that supernet routes, including 0.0.0.0/0, are not listed within
any
classful section -- they are listed separately, on their own.
What the router does, with
no ip classless
set, is to first check to see if the target address in question falls
within one of these "known" sections -- i.e., in one of the "known"
classful networks. If so, he will use the *longest* match for the
target
address that he can find in that section.
(Note that this is a point also often left out of the text books.
Remember: a router will *always* try to do a longest-prefix match,
except for the constraint mentioned here, for 'no ip classless.
)
*But*, he will *not* look *outside* that section (classful network),
when
no ip classless
is set.
With the advent of the Internet and CIDR and "prefixes", the above logic
may not be good enough. When considering a given prefix and because of
the vagaries of the way addresses were handed out in the beginning, it
is very possible that "subnets" of that prefix (addresses with a longer
prefix, but yet still matching the original prefix in question) may
be disconnected. Of course, this is a situation that is trying to be
remedied, but it is still possible.
So, now, it is very desirable to try "supernet" routes, in particular
the ever-hopeful "default" route, 0.0.0.0/0.
(Actually, in this "prefix" environment, the concept of "supernet"
and "subnet" disappear. Every route is simply a summary or
aggregate route to a bunch of possible addresses.
)
This is what
ip classless
does. It allows the router look *outside* the classful &
RE: The Finale: OSPF and IP Classless (partial retraction)
Geez, you're right. I'm starting to miss the forest because I've looked at too many trees! Yes, even in my experiments, I now remember seeing that the router would pick a supernet route for a specific major network. Others pointed this out to me and I had completely forgotten that particular point. The moral of the story is: always use 'ip classless' and then quit worrying about it. >From here onward I will no longer refer to 'ip classless'.it is now 'ip clueless'. :-) >>> "Bob Vance" <[EMAIL PROTECTED]> 3/30/01 11:22:53 AM >>> Actually, John my treatises :) on this subject a year ago showed this. ip classless *only* affects the lookups *outside* the classful aggregate. Any supernet *within* the classful aggregate *will* be used, even with no ip classless set. Thus, a learned route, 10.1.0.0/16 , will be used for address 10.1.1.1 , but not 10.2.2.2 . (*if* I still understand what I wrote below ;>). Here is part of my original work on the subject for those who are feeling drowsy, but just can't nod off completely ;>) Thanks to the lab of Ding So I was able to pound the last nail in the coffin of how [no] ip classless affects route lookups (the doco makes no mention of route installation, so we would guess that it has no effect. Further investigation will be required to confirm/debunk this). I will do a little write up, here, that can be challenged by anyone with a dash of temerity: (Note that I've tried several times and I just can't seem to find a clear, yet succinct way to describe this. ) == Under old, classful routing it was assumed that all local networks would be subnets of one or a couple of classful networks and that all the subnets of a particular classful network, say "X" (e.g., X=172.16.0.0), would be "connected" to each other. What this means is that, for each and every pair of subnets of classful network "X", there would be an interconnecting path among 1 or more routers, that could be traversed *entirely* on segments whose IP network addresses are subnets of classful network "X". If the above requirement does not obtain, i.e., if the network path *must* include a subnet of a *different* classful network, say "Y", then we call this situation "a discontiguous network". or "X has discontiguous subnets" or "X has disconnected subnets" . Another assumption in this environment is that, if we (a router) know about any particular subnet of "X", then we should know about *all* subnets of "X" that actually exist; either by our having one or more interfaces within a subnet of X, an admin giving us proper static routes, or by information received from a routing protocol. With the above in mind, the router will not entertain a route to a subnet of network "Y" that isn't a route to a network address *within* network "Y" (it can be that actual network aggregate, itself; e.g., a route to 172.16.0.0/16, in the above example) -- that would mean discontiguity. In particular, it will *not* consider the "default" route 0.0.0.0/0 for any address within classful Y, if it has information about at least one subnet of Y. In addition (and this is the one always left out of the textbooks), it will not consider *any* *supernets* routes of Y. The 0.0.0.0/0 is just a particular case of this rule (0.0.0.0/0 is always a supernet of *every* network address -- it contains *0* bits that do not match). If you look at a show ip route you'll notice that the table is broken up into sections at *classful* network boundaries, *even* if ip classless is set. Note that supernet routes, including 0.0.0.0/0, are not listed within any classful section -- they are listed separately, on their own. What the router does, with no ip classless set, is to first check to see if the target address in question falls within one of these "known" sections -- i.e., in one of the "known" classful networks. If so, he will use the *longest* match for the target address that he can find in that section. (Note that this is a point also often left out of the text books. Remember: a router will *always* try to do a longest-prefix match, except for the constraint mentioned here, for 'no ip classless. ) *But*, he will *not* look *outside* that section (classful network), when no ip classless is set. With the advent of the Internet and CIDR and "prefixes", the above logic may not be good enough. When considering a given prefix and because of the vagaries of the way addresses were handed out in the beginning, it is very possible that "subnets" of that prefix (addresses with a longe
RE: The Finale: OSPF and IP Classless (partial retraction)
>it is now 'ip clueless'. :-) LOL - Tks | <mailto:[EMAIL PROTECTED]> BV | <mailto:[EMAIL PROTECTED]> Sr. Technical Consultant, SBM, A Gates/Arrow Co. Vox 770-623-3430 11455 Lakefield Dr. Fax 770-623-3429 Duluth, GA 30097-1511 = -Original Message- From: John Neiberger [mailto:[EMAIL PROTECTED]] Sent: Friday, March 30, 2001 1:40 PM To: [EMAIL PROTECTED] Cc: [EMAIL PROTECTED] Subject: RE: The Finale: OSPF and IP Classless (partial retraction) Geez, you're right. I'm starting to miss the forest because I've looked at too many trees! Yes, even in my experiments, I now remember seeing that the router would pick a supernet route for a specific major network. Others pointed this out to me and I had completely forgotten that particular point. The moral of the story is: always use 'ip classless' and then quit worrying about it. >From here onward I will no longer refer to 'ip classless'.it is now 'ip clueless'. :-) _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
