INE WB Vol1 - 5.22. EIGRP Filtering with Extended Access-Lists

Like RIP, extended access-lists when called as a distribute-list in IGP have a
different meaning than in redistribution or as in BGP. With BGP and
redistribution the “source” field in the ACL represents the network address, and
the “destination” field represents the subnet mask. In IGP distribute-list
application the “source” field in the ACL matches the update source of the route,
and the “destination” field represents the network address. This implementation
allows us to control which networks we are receiving, but more importantly who
we are receiving them from. Before the filter is applied, R5 routes as follows.