EIGRP filters

murray.bown · ‎12-10-2007

Hi Guys

I have a situation where I need to prevent EIGRP routing updates being received by my local network routers from an other router that I have no control over, however I still want to receive updates of all the external routes from this other router. My network is on 172.19.0.0/16 which is variably subnetted into 21 subnets and 5 masks.

Thanks for looking

Murray

mohammedmahmoud · ‎12-10-2007

Hi Murray,

I think we need more details about the case, but as a general answer, you can simply use distribute-list to filter the desired incoming updates from a certain neighbor:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios124/124cr/hirp_r/rte_pih.htm#wp1122418

Router(config)#router eigrp 10

Router(config-router)#distribute-list ?

<1-199> IP access list number

<1300-2699> IP expanded access list number

WORD Access-list name

gateway Filtering incoming updates based on gateway

prefix Filter prefixes in routing updates

route-map Filter prefixes based on the route-map

HTH,

Mohammed Mahmoud.

murray.bown · ‎12-10-2007

Hi Mohammed

Firstly congratulations on your CCIE, just read about it on the forum, good work.

So I have tried to lab this out on another router and have managed to work out the distribute-list to filter out unwanted networks. In my situation I have two routers, one being my core router and another device that acts as a backup network running EIGRP on AS 2000 so I need these two devices to exchange routing updates so my question is how would I filter out updates for only the foreign router, does this make sense?

mohammedmahmoud · ‎12-10-2007

Hi Murray,

Thank you very much.

I can't imagine your full scenario, especially this part "and another device that acts as a backup network running EIGRP on AS 2000" and this part "I need these two devices to exchange routing updates so my question is how would I filter out updates for only the foreign router", if you may please elaborate more, mainly how are they connected and how is the foreign router connected to them.

With the distribute-list you can control which specific routes (prefix) to be filtered from which specific routers (gateway).

Router(config-router)#distribute-list prefix <> gateway <> in

HTH,

Mohammed Mahmoud.

murray.bown · ‎12-10-2007

OK they say a picture speaks volumes so see the attached jpg. :-)