From: Paul Borghese (pborghese@xxxxxxxxxxxxxx)
Date: Wed Jun 13 2001 - 09:31:13 GMT-3
In RIP V1 there is an assumption of a constant subnet mask. Therefore when
RIP is advertised, you only advertise the routes, and do not include the
subnet mask. If you are a router receiving the advertisements, you look at
your own interfaces to find the correct subnet. If you do not have that
network on any of your interfaces you assume the classfull boundary.
If the router has 10.0.0.0 and 10.0.1.0 configured, both as a /24, you
should see both routes announce. But you will not see the subnet included.
Paul Borghese
----- 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
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