Re: Ip subnet Zero & Ip classess [7:35340]
Ok, try this Ip- classless: allows a router to look for routes classlessly (understands subnets) meaning it will do a longest bit match with routes in your routing table but if after checking for subnets it doesn't find one locally then it follows the default route. With out this command the router would still do a longest bit match but doesn't understand subnets, and would check for a subnet if it is not local to your router it would be dropped. Ip subnet-zero- This allows the use of the zero subnet and the ip addresses in that range. take for instance you have a 10.1.1.0/24 and you decided to break that up into 2 networks. the network would be 10.1.1.64/26 and 10.1.1.128/26 you have lost two networks network 10.1.1.0/26 (.1-.62, 63 is broadcast) and its ip addresses and 10.1.1.192/26 (.193-254, 255 is broadcast) and its ip addresses. PING wrote: >ip classless is used to tell the routing protocols which supports VLSM that >subnet should be sdvertised as part of the route. ip classfull on the other >hand >is used to restrict to use major class subnet mask. > >Nadeem >== > >Arnaldo Gomez wrote: > >>Can someone give a gerneral explanation on these two commands? >> >>ip subnet-zero >>ip-classless >> >>What do they do and why would you use them? >> >>Thanks. >> >>Arnaldo >> >-- > >Ishrat Nadeem Zahid >CCNP >Cisco Systems,Inc. >Chelmsford, MA 01824 Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=35370&t=35340 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Ip subnet Zero & Ip classess [7:35340]
ip classless is used to tell the routing protocols which supports VLSM that subnet should be sdvertised as part of the route. ip classfull on the other hand is used to restrict to use major class subnet mask. Nadeem == Arnaldo Gomez wrote: > Can someone give a gerneral explanation on these two commands? > > ip subnet-zero > ip-classless > > What do they do and why would you use them? > > Thanks. > > Arnaldo -- Ishrat Nadeem Zahid CCNP Cisco Systems,Inc. Chelmsford, MA 01824 Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=35348&t=35340 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Ip subnet Zero & Ip classess [7:35340]
subnet zero lets you do this: ip address 192.168.1.1 255.255.255.252 ip classless lets you do this ip address 192.168.1.1 255.255.0.0 and probably more importantly it will allow a router to forward a packet via a default route even though router is connected to a subnet of the major network your trying to reach, i.e. discontiguous. Dave Arnaldo Gomez wrote: > > Can someone give a gerneral explanation on these two commands? > > ip subnet-zero > ip-classless > > What do they do and why would you use them? > > Thanks. > > Arnaldo -- David Madland Sr. Network Engineer CCIE# 2016 Qwest Communications Int. Inc. [EMAIL PROTECTED] 612-664-3367 "Emotion should reflect reason not guide it" Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=35344&t=35340 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Ip subnet Zero & Ip classess [7:35340]
Well, From http://www.cisco.com/univercd/cc/td/doc/product/software/ios120/12cgcr/np1_r /1rprt2/1ripadr.htm#xtocid12 : ip classless At times the router might receive packets destined for a subnet of a network that has no network default route. To have the Cisco IOS software forward such packets to the best supernet route possible, use the ip classless global configuration command. To disable this feature, use the no form of this command. Regarding subnet zero, the IOS didn't used to let you assign an address that was part of subnet zero. It wasn't allowed because it could create an address that was the same as the subnet address. Here's a link from cisco with more lovely info about that and the all one's subnet: http://www.cisco.com/warp/public/105/40.html -Original Message- From: Arnaldo Gomez [mailto:[EMAIL PROTECTED]] Sent: Wednesday, February 13, 2002 1:45 PM To: [EMAIL PROTECTED] Subject: Ip subnet Zero & Ip classess [7:35340] Can someone give a gerneral explanation on these two commands? ip subnet-zero ip-classless What do they do and why would you use them? Thanks. Arnaldo Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=35343&t=35340 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Ip subnet Zero & Ip classess [7:35340]
This is definitely a topic where you should search the archives. There have been some excellent discussions in the past that have resulted in some great explanations of each of these commands. It would be better for you to read them than to have the original posters type them in all over again. :-) Regards, John >>> "Arnaldo Gomez" 2/13/02 2:44:37 PM >>> Can someone give a gerneral explanation on these two commands? ip subnet-zero ip-classless What do they do and why would you use them? Thanks. Arnaldo Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=35342&t=35340 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Ip subnet Zero & Ip classess [7:35340]
Can someone give a gerneral explanation on these two commands? ip subnet-zero ip-classless What do they do and why would you use them? Thanks. Arnaldo Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=35340&t=35340 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: ip subnet-zero
Could you please pass the url for the web-page? Thanks in advance. Brian Lodwick wrote: > > Group, > I feel like I have come to a nice understanding on this issue. Many thanks > to Howard Berkowitz, Radia Perlman's book, and I must apologize there was > another groupstudy member who referrenced a webpage that was really > helpfull, but I can't remember his name. > If anyone is interested this is what I have come to understand. > This as Howard had mentioned is only applicable in a classfull environment. > There are infact good reasons why the all 0's subnet was not used and why > the all 1's subnet was not used. These weren't hard and fast rules, but were > emphatically reccomended in a classfull environment. The reason being that > when routing information is distributed in a classfull environment the > prefixes aren't sent and defualt barriers are set for the masks. In the > instance where an all 0's subnet was used there would be no way to decipher > between say > 192.168.15.0/24 and 192.168.15.0/28 sent in a routing update. > The all 1's subnet is a similar issue accept in this instance it would not > be possible to send a routing update to indicate subnet multicasts. > This is quite an interesting concept and I appreciate everyones help > understanding this issue. > > >>>Brian > > >From: "Donald B Johnson Jr" <[EMAIL PROTECTED]> > >Reply-To: "Donald B Johnson Jr" <[EMAIL PROTECTED]> > >To: "Brian Lodwick" <[EMAIL PROTECTED]>, <[EMAIL PROTECTED]> > >Subject: Re: ip subnetting > >Date: Wed, 27 Dec 2000 10:02:42 -0800 > > > >you can break it down with vlsm and reclaim most of the space.Duck > >- Original Message - > >From: Brian Lodwick <[EMAIL PROTECTED]> > >To: <[EMAIL PROTECTED]> > >Sent: Wednesday, December 20, 2000 4:25 AM > >Subject: ip subnetting > > > > > > > Group, > > > In determining valid subnetworks it used to be true all were valid > >accept > > > the all 1's subnet and the all 0's subnet. In an environment where all > > > devices are compatible, I understand, that by using the configuration > > > command "ip subnet-zero" it enables the use of the all 0's subnet. The > > > question I ask then, wouldn't that leave the all 1's subnet still an > >invalid > > > subnet even when using the previous mentioned command? or is there > >something > > > else that allows the all 1's subnetwork? I have been asked this > >question, > > > and I don't feel I am correct. The new formula noted in the CCNA book > >notes > > > the new equation for determining the amount of valid subnetworks is 2^# > >of > > > subnet bits, and I figured it would be 2^#of subnet bits - 1 (for the > >all > > > 1's subnet). I don't pose this question without first a bit of research > >and > > > everything I have read indicates the "ip subnet-zero" command only > >enables > > > the use of the all 0's subnetwork. I however cannot find anything > >indicating > > > the use of the all 1's subnet is permitted. Any help is appreciated. > > > > > > >>>Brian > > > _ > > > Get your FREE download of MSN Explorer at http://explorer.msn.com > > > > > > _ > > > 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] > > _ > Get your FREE download of MSN Explorer at http://explorer.msn.com > > _ > FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] -- Shabbir S. Talib MCSE, CNE, CCNA _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
ip subnet-zero
Group, I feel like I have come to a nice understanding on this issue. Many thanks to Howard Berkowitz, Radia Perlman's book, and I must apologize there was another groupstudy member who referrenced a webpage that was really helpfull, but I can't remember his name. If anyone is interested this is what I have come to understand. This as Howard had mentioned is only applicable in a classfull environment. There are infact good reasons why the all 0's subnet was not used and why the all 1's subnet was not used. These weren't hard and fast rules, but were emphatically reccomended in a classfull environment. The reason being that when routing information is distributed in a classfull environment the prefixes aren't sent and defualt barriers are set for the masks. In the instance where an all 0's subnet was used there would be no way to decipher between say 192.168.15.0/24 and 192.168.15.0/28 sent in a routing update. The all 1's subnet is a similar issue accept in this instance it would not be possible to send a routing update to indicate subnet multicasts. This is quite an interesting concept and I appreciate everyones help understanding this issue. >>>Brian >From: "Donald B Johnson Jr" <[EMAIL PROTECTED]> >Reply-To: "Donald B Johnson Jr" <[EMAIL PROTECTED]> >To: "Brian Lodwick" <[EMAIL PROTECTED]>, <[EMAIL PROTECTED]> >Subject: Re: ip subnetting >Date: Wed, 27 Dec 2000 10:02:42 -0800 > >you can break it down with vlsm and reclaim most of the space.Duck >- Original Message - >From: Brian Lodwick <[EMAIL PROTECTED]> >To: <[EMAIL PROTECTED]> >Sent: Wednesday, December 20, 2000 4:25 AM >Subject: ip subnetting > > > > Group, > > In determining valid subnetworks it used to be true all were valid >accept > > the all 1's subnet and the all 0's subnet. In an environment where all > > devices are compatible, I understand, that by using the configuration > > command "ip subnet-zero" it enables the use of the all 0's subnet. The > > question I ask then, wouldn't that leave the all 1's subnet still an >invalid > > subnet even when using the previous mentioned command? or is there >something > > else that allows the all 1's subnetwork? I have been asked this >question, > > and I don't feel I am correct. The new formula noted in the CCNA book >notes > > the new equation for determining the amount of valid subnetworks is 2^# >of > > subnet bits, and I figured it would be 2^#of subnet bits - 1 (for the >all > > 1's subnet). I don't pose this question without first a bit of research >and > > everything I have read indicates the "ip subnet-zero" command only >enables > > the use of the all 0's subnetwork. I however cannot find anything >indicating > > the use of the all 1's subnet is permitted. Any help is appreciated. > > > > >>>Brian > > _ > > Get your FREE download of MSN Explorer at http://explorer.msn.com > > > > _ > > 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] _ Get your FREE download of MSN Explorer at http://explorer.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 SUBNET-ZERO
Check the IP address to see if it falls on a network boundary.. eg. 192.168.1.16 with 28 bit mask 192.168.1.32 with 28 bit mask 150.49.5.136 with 30 bit mask of course assuming ip subnet-zero command is used.. you will not get the "bad mask" error.. "Gert Jan" <[EMAIL PROTECTED]> on 19/07/2000 17:16:52 Please respond to "Gert Jan" <[EMAIL PROTECTED]> To: [EMAIL PROTECTED] cc: (bcc: Mark Vicuna/Sydney/CDM) Subject: IP SUBNET-ZERO Hi all, What is the best way to determine if an ip/subnet is an ip subnet-zero address? Thanks, Peter ___ 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 SUBNET-ZERO
Strongly discouraged as all ones ip-subnet. Otherwise, you'd refer to the classfull address. cvp ___ 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 SUBNET-ZERO
Hi all, What is the best way to determine if an ip/subnet is an ip subnet-zero address? Thanks, Peter ___ 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 subnet-zero command??
In IP rules it is not possible to use a zero-subnet. If you wanna overrule this, use it anyway (and why not :-) ) and place a interface anyway in it you must invoke the ip subnet-zero command. Try subnetting a IP subnet and without the ip subnet-zero command set an ip address on a interface in the zero subnet, you'll find out why you need it. :) Ruud -Oorspronkelijk bericht- Van: Palikhey, Niraj [mailto:[EMAIL PROTECTED]] Verzonden: woensdag 21 juni 2000 18:43 Aan: '[EMAIL PROTECTED]' Onderwerp: ip subnet-zero command?? Hi, Had a question on ip subnet-zero? It is on by default when you first configure a router? Why would I want it or better still, why would I not want it? Please advise. Thank you. Kind regards, Niraj ___ 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]
ip subnet-zero command??
Hi, Had a question on ip subnet-zero? It is on by default when you first configure a router? Why would I want it or better still, why would I not want it? Please advise. Thank you. Kind regards, Niraj ___ 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]
