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Can I use the distribute-list in/out command with OSPF to filter routes?

April 26, 2017Command filter ospf routes

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Can I use the distribute-list in/out command with OSPF to filter routes?

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A. The distribute-list commands are supported in OSPF but work differently than distance-vector routing protocols such as Routing Information Protocol (RIP) and Enhanced Interior Gateway Routing Protocol (EIGRP). OSPF routes cannot be filtered from entering the OSPF database. The distribute-list in command only filters routes from entering the routing table; it does not prevent link-state packets from being propagated. Therefore, this command does not help conserve router memory, and it does not prohibit a router from propagating filtered routes to other routers. Caution: Use of the distribute-list in command in OSPF may lead to routing loops in the network if not implemented carefully. The command distribute-list out works only on the routes being redistributed by the Autonomous System Boundary Routers (ASBRs) into OSPF. It can be applied to external type 2 and external type 1 routes, but not to intra-area and interarea routes.