RIP (or any other IGP) route filtering using Extended ACL

August 3, 2008 at 3:53 pm | Posted in Routing | Leave a comment

This example is to prevent the route 150.1.7.0/24 learnt via router 155.1.0.1 off interface Serial0.

access-list 199 deny  ip host 155.1.0.1 host 150.1.7.0
access-list 199 permit ip any any

router rip
version 2
network 150.1.0.0
network 155.1.0.0
distribute-list 199 in Serial0
no auto-summary

I usually make mistake with creating extended ACL for this purpose. I do
tend to put learnt route as source address of ACL, before the gateway
(destination address). The right ACL should be created in the
reverse order, as above.

NOTE that:

Extended ACL when called as a distribute-list in IGP have a different meaning than in redistribution or as in BGP.

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