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Complex Rip update filter


I have following network scheme

I have 7 routers names R1 to R7 connected to R10000.

R10000 is also connected to R100 and R200, and R300

All routers are using RIP as routing protocol. I don't want any routes of R1 on R2 and vice-versa . (Same thing between R1,R2,R3,R4,R6,R7)

Routers Rx ( x=1 to 7) need only to learn routes from R100,R200 and R300.

In my case I have contigues network in Rx and R300.

Per example, on R1, I have network and in R300 , I have,

How can I filter RIP update to Rx ?

What is the simple way to filter rip update in my case ?

Distribute-list with an access-list or prefix-list is harder, because of R300 (R300 contains more than 2000 routes)

2 Replies 2


Is the addressing just an example as you will be potentialy overlapping address space due to the supernet. This may lead to a discontigous networks etc.

Distribute lists with access-lists is probably simpler with some good masking if you are attempting to filter particular networks.

If its all updates from specific neighbors you could utilise passive-interfaces to prevent sending updates, or distance 255 on the receiving router for the specific neighbor if not all sources for that network are be filtered.

Hope this helps.


In your case, i guess the topology is a star topology with R1 through R7 connected point to point to R10000 and also R100, 200 and 300 connected p-p to R10000.

So The main point of route exchange is R10000.

On each outgoing interface of R10000 to the Rx routers, apply distribute list on the RIP process.

router rip

distribute-list 10 out s0

distribute-list 20 out s1




access-list 10 deny x.x.x.x

access-list 10 deny y.y.y.y



access-list 10 permit any

access-list 20 deny y.y.y.y

access-list 20 deny .z.z.z.z



access-list 20 permit any

Each accesslist 10, 20 is for respective routers R1, R2 etc....

On access-list 10 for R1 deny all other networks from R2 through R7 and the last Permit statement would match routes from R100, 200 and 300.

The above method might help you only , if the number of routes, advertised by each Rx is few in number, otherwise your access-list would be too big to be configured.

Also I would advise you to enable RIP version 2, and use some sort of summarization, to reduce the number of routing table entries you have.

Sankar Nair
UC Solutions Architect
Pacific Northwest | CDW
CCIE Collaboration #17135 Emeritus
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