Route filtering prefix lists

- [Instructor] Route filtering is also a strength of EIGRP.…It gives an administrator the ability…to filter routes inbound or outbound…on any router in the network.…This may not seem like a major feat,…but this flexibility is something that OSPF sorely lacks.…Filtering is accomplished via distribute lists.…These lists will reference an ACL,…prefix list, or a route map.…Filtering via ACL is done with either…a numbered or named standard access list.…

A permit clause allows prefixes,…while a deny clause will filter prefixes.…Using this familiar diagram,…I'll have Router 2 filter 192.168.1.0/28 over to Router 1.…This can be done from Router 2 out to Router 1,…or inbound on Router 1.…But in this case, I'll apply filtering on Router 2 outbound.…First, I'll verify the topology table on Router 1.…show ip eigrp top all.…

Make note of the entries for the prefix in question.…Next on Router 2, I'll create a named list.…ip access-list,…we'll make it standard.…And we'll call it filter-to-1.…I'll then block the prefix in question.…