Route redistribute, filtering notes

On a router, redistribute protocol A in to protocol B

Following routes will be distributed into protocol B:
1. all interfaces which running protocol A (exclude ISIS/ODR)
2. all routes learned from protocol A

In case of mutual redistribution at multiple redistribution points, be careful when distribute from a preferred (AD) protocol into a less preferred protocol (e.g from OSPF into RIP)

Because link state protocols do not advertise routes from their routing table as do distance vector protocols, there are no updates to filter. Because of this behavior, route filters are mostly used at redistribution points into link state domains, such as an OSPF ASBR, where they can regulate which routes enter or leave the domain. Within the link state domain, route filters have limited utility.

From Routing TCP.IP