I enjoyed Petr's article regarding explicit next hop. It reminded me of a scenario where a redistributed route, going into OSPF conditionally worked, depending on which reachable next hop was used. Here is the topology for the scenario: Here is the relevant (and working :)) information for R1.
OSPF FA Overview This post is dedicated to one “esoteric” OSPF external route filtering method based on hiding OSPF Forwarding Address. Recall the meaning of OSPF FA. This is a special field used on OSPF type 5 and 7 LSAs to convey the information of the “external route source”. The purpose of FA is to optimize forwarding in situations where the external route source is connected to a shared segment. Here is an example: