[c-nsp] Filtering incoming advertisements in RIP

Bernhard Schmidt berni at birkenwald.de
Tue Jan 23 11:19:11 EST 2007


Hi everyone,

we are running a campus network with several 6500 Sup720-A boxes on
12.2(18)SXF7 mostly. We have a few connected entities (student dorms
with laser links mostly) which have a backup connection through a tunnel
(over DSL) to us.

Due to the hardware being available on the student dorm side (mostly old
hardware routers) RIPv2 was the choice of dynamic routing protocol to be
used on the primary link. The switchover to the backup path is then done
with static routes with a lower admin distance.

Unfortunately, in this case we have a severe problem filtering incoming
RIP advertisements. The network statements in the router rip context are
classful (ewww), so when I want to enable RIP on the /30 transfer
network within 10/8, I have 30 other interfaces also within 10/8
suddenly speaking RIP. Great.

So my next try was the obvious one

| router rip
|  distribute-list prefix DORM in Vlan916
|  distribute-list prefix DENY-ALL in

again, this obvious solution failed as the latter command seems to
override the first one. At least, as soon as I add the second line,
incoming RIP updates are ignored.

Any other ideas? There are no usable RIP specific commands on the
interface level, and I obviously don't want to list all interfaces on
that router with a distribute-list line each.

Regards,
Bernhard


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