OSPF Route Filtering
In this article, we are going to learn how to configure OSPF route filtering. We will learn how to do that within an area first then between areas. Network topology We will use the following topology. Everything is done in GNS3. I am using the IOS image C3725-ADVENTERPRISEK9-M version 12.4(15)T5 on all the routers. Figure1: network topology In order to reproduce this topology, I added the base configuration of each router in the bottom of the article. Routers R1, and R2 are in OSPF area 0 . R5 is in area 3. R3 and R4 are ABR s and have LSA s from both areas. Figure 2: distinguishing the area border routers in the network topology Intra-area OSPF route filtering using prefix lists and distribute lists Intra-area route filtering means that we will manipulate OSPF routes within an area. This technique prevents a router from installing a particular network prefix into the routing table. Remember that an OSPF router maintains the link state database distinct from the routing table. So all l...