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Community Member

Filtering out routing updates

I have 3 routers sitting on the same lan sharing the same subnet. Router A and B participate in HSRP and connect to the company network with visibility of the full IP network but Router C is attached to an external network. I do not want routes from Router A and B to propogate to Router C but I do want visibility of subnet physically connected to Router C.

What is the best soluton?

3 REPLIES

Re: Filtering out routing updates

WHich routing protocol are you using.

You can use a outbound filter on A and Bs interface which will filter the desired routes. Permit only what is wanted.

access-list 10 permit

router

distribute-list 10 out

If you use OSPF then, filtering using a outbound filter wont work. So what you need to do is configure inbound distribute list at C and filter necessary routes that are coming from A and B. This is because, distribute list filters work on routing tables and not on LSAs. OSPF sents routing entries as LSAs unlike, other routing protocols.

Community Member

Re: Filtering out routing updates

i'm not sure but cant you set that int as passive that way updates will not be sent out of that interface

Re: Filtering out routing updates

This would work fine for protocols such as RIP/IGRP. But for those protocols like EIGRP and OSPF this wont work, as it would remove the neighbor relationship also. He has not specified which routing protocol he is using.

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