In OSPF, routers from down to full state,what's kind of networks(broadcast multicast unicast) used per state to exchange information? I always heard 224.0.0.5 and 224.0.0.6 these two address, and was told those two multicast address is the most difference with RIPV1(Because rip1 use broadcast), so does that mean in OSPF routers always use these two multicast address to exchange information? If that, But why still seen broadcast and unicast in OSPF? I got confused!
Routing – Broadcast,multicast and unicast in OSPF
ospfrouting
Best Answer
Multicast address 224.0.0.5 is used for neighbor discovery (Hello messages). Then database exchange is made on a peer to peer basis (with ip address of routers).
The kind of OSPF networks is mostly used to indicate how each neighbor will communicate with other neighbors. For example, in broadcast mode, A router is designated to be the the hub for database exchanges with other neighbors (DR). And a backup router (BDR) is also designated in case of failure of the DR.