From: Charles Ryan (chuckster_31@xxxxxxxxx)
Date: Tue Jun 12 2001 - 23:49:11 GMT-3
Jason,
In order to get your two loopbacks to be announced as /24's, they would need
to be part of the same major class network as your wan connections or
point-to-point links, not to mention, have the same network mask (if I'm not
mistaken). Look at the diagram below:
10.0.1.0/24 --lo0
-----R1----------------T1-----------------R2----
---lo0----x.x.x.x
10.0.2.0/24 --lo1 10.0.3.1/24 10.0.3.2/24
R1 and R2 are connected via a T1, and their ip addresses are 10.0.3.1/24 and
10.0.3.2/24 respectively. Since the loopback interfaces are part of the same
major network as the wan interface (ie. they are part of the 10.0.0.0
network, and each are /24), then the subnets on the loopbacks should be
announced as /24's. Now, on the other hand, if the wan connection is a
different major network (ie. 11.0.0.0), then the router will announce the
loopbacks at the major network boundary (10.0.0.0/8).
Someone please correct me if I'm wrong, or feel free to add more
clarification.
-Chuck Ryan
----- Original Message -----
From: "Jason Gardiner" <gardiner@sprint.net>
To: <ccielab@groupstudy.com>
Sent: Tuesday, June 12, 2001 10:16 PM
Subject: RIP/IGRP Clarification
> All,
>
> Several books from which I study explain RIP and IGRP FLSMs in a manner
> similar to this quote:
>
> "When subnetting is performed in a RIP or IGRP environment, all subnet
> masks for a given classful address must be the same. They are "fixed
> length subnet mask" (FLSM) environments. Also, for RIP and IGRP, all
> subnets of a given classful network must be the same."
>
> To me, this sounds like you can break up a network like 10.0.0.0 into /24s
> and have them announced across a RIP or IGRP network. Each subnet has the
> same mask.
>
> I've tried it and run a debug. The only block announced is a /8, but the
> routing table shows
>
> 10.0.0.0/24 is subnetted, 2 subnets
> 10.0.0.0 is directly connected, Loopback 0
> 10.0.1.0 is directly connected, Loopback 1
>
>
> It appears that the protocol still announces based on the 3 bit classful
> boundary and ignores the subnet information.
>
> Am I missing something, or is the information in the quote wrong?
>
>
>
> Thanks,
>
> Jason Gardiner
> Engineering Services
> Sprint E|Solutions
>
> "The only thing to prevent what's past is to put a stop to it before it
happens."
> - Sir Boyle Roche
> **Please read:http://www.groupstudy.com/list/posting.html
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