Re: ip classless

[Francisco Muniz]

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.

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RE: ip classless

[Yee, Jason]

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


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RE: IP Classless

[Daniel Cotts]

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
> 
> 
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Re: IP Classless

[Shane Stockman]

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
>
>
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Re: IP Classless

[Frank B.]

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

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Re: IP Classless

[Sam LI]

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
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Re: IP Classless

[EA Louie]

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
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Re: IP Classless

[Priscilla Oppenheimer]

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
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Re: ip classless

[cv . perez]

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

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Re: ip classless ?

[Casey Fahey]

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
>
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RE: ip classless ?

[Sam Adams]

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

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Re: ip classless ?

[Adam Hickey]

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
>
> ___
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Re: ip classless ?

[whatshakin]

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
> >
> >___
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Re: ip classless ?

[Adam Hickey]

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
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> >
>
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RE: ip classless ?

[David Jones]

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]
>
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RE: ip classless ?

[dacarl4]

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 ?

[Casey Fahey]

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]
> >
>
>___
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Re: ip classless ?

[Ovate]

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 ?

[whatshakin]

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 ?

[Matt Gravlin]

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
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Re: ip classless ?

[GNOME]

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]
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RE: ip classless ?

[Chuck Larrieu]

-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]
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RE: ip classless ?

[Erick B.]

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. 



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RE: IP Classless [7:616]

[Bob Vance]

>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




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RE: IP classless/Default routes

[Emilia Lambros]

 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

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Re: IP classless/Default routes

[Kenny Sallee]

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
>
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Re: IP classless/Default routes

[Donald B Johnson Jr]

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
>
> ___
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RE: IP classless/Default routes

[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

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Re: IP classless/Default routes

[Adam Hickey]

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
>
> ___
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RE: IP classless/Default routes

[Chuck Larrieu]

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

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RE: IP classless/Default routes

[Fomes Iain]

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]
> 
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RE: IP classless/Default routes

[William Swedberg]

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
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> http://www.groupstudy.com
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> to [EMAIL PROTECTED]
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> 
> 
> 


=
William Swedberg CCNP CCDP

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RE: IP classless/Default routes

[Karen . Young]

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

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RE: IP classless/Default routes

[Cohen, Michael]

r the link is brought back up, issue a
shutdown-no shutdown command on the interface that points to the current
default gateway.

Router#conf
Configuring from terminal, memory, or network [terminal]?
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#int e0/1
Router(config-if)#shutdown
Router(config-if)#
00:24:35: %LINK-5-CHANGED: Interface Ethernet0/1, changed state to
administrativ
ely down
00:24:36: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0/1,
changed s
tate to down
Router(config-if)#no sh
Router(config-if)#
00:24:49: %LINK-3-UPDOWN: Interface Ethernet0/1, changed state to up
00:24:50: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0/1,
changed s
tate to up
Router(config-if)#^Z
Router#
00:24:55: %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 this will insert our original Gateway of last resort.
Sorry for the HTML but I wanted to use color to illustrate the key commands
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]
>
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RE: IP classless/Default routes

[Timmons, Robert]

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

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RE: ip classless, Not exactly correct

[Tom Pruneau]

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

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RE: IP Classless Revisited (More info)

[John Neiberger]

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
>  >  
>  >  
>  >  
>  >  
>  >  
>  >  ___
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>  
>  
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Re: IP Classless Revisited (More info)

[Vincent]

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 10.5.5.5 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
> >  >
> >  >
> >  >
> >  >
> >  >
> >  >  ___
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[EMAIL PROTECTED]
> >
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Re: IP Classless Revisited (More info)

[John Neiberger]

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 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

RE: IP Classless Revisited (More info)

[Bob Vance]

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)

[John Neiberger]

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

Re: IP classless command [7:30056]

[Mike]

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




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Re: IP classless command [7:30056]

[Mr. Richard L. Pickard]

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




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Re: IP classless command [7:30056]

[Michael Paulson]

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]




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Re: IP classless command [7:30056]

[Hunt Lee]

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




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RE: IP classless command [7:30056]

[Dave]

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




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RE: IP classless command [7:30056]

[Bernard Omrani]

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]




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RE: IP classless command [7:30056]

[[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]




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Re: IP classless command [7:30056]

[Dan Garfield]

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]




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RE: IP Classless Revisited (this is just odd...)

[YY]

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





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RE: IP Classless Revisited (this is just odd...)

[John Neiberger]

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
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RE: IP Classless Revisited (this is just odd...)

[John Neiberger]

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

>





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Re: IP Classless Revisited (this is just odd...)

[Circusnuts]

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
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> >
> >
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>
>
>
>
>
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RE: IP Classless Revisited (this is just odd...)

[Peter Van Oene]

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/
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>
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RE: IP Classless Revisited (this is just odd...)

[John Neiberger]

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
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>  >
>  >
>  >_
>  >FAQ, list archives, and subscription info:
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>  >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
>  
>  
>





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RE: ip classless and default route [7:53231]

[Priscilla Oppenheimer]

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)




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Re: ip classless and default route [7:53231]

[Erick B.]

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)
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RE: ip classless and default route [7:53231]

[cebuano]

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)




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RE: IP Classless (from Q&A Forum at Cisco)

[Chuck Larrieu]

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.




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