The EOS implementation of OSPF uses an alternate Area Border Router (ABR) behavior as specified in the IETF draft document. This is implemented as an optimization over the standard OSPF so that the packets would not be dropped when a router loses Active backbone connection which could otherwise be successfully forwarded.

In an OSPFv2 Area Border Router (ABR), area filters may be used to prevent specific prefixes from being announced by an area as Type 3 Summary LSAs or routes to AS boundary routers as Type-4 ASBR summary LSAs.

In an OSPFv3 Area Border Router (ABR), area filters may be used to prevent specific prefixes from being announced by an