Cisco CCNA 200-301 Practice Question

When a neighbor remains in the INIT state, the local router is receiving OSPF hello packets from its peer, but the peer is not acknowledging the local router by listing its router ID in its own hellos. One of the most frequent reasons for this one-way communication is that authentication is enabled on only one side or the passwords differ. The router that expects authentication silently drops the non-authenticated hellos it receives, so the peer never learns about them and never lists the local router in its hello packets, leaving the session in INIT.

By contrast, mismatched hello/dead timers, MTU problems, or network-type mismatches normally prevent either side from accepting the other's hellos at all, so no neighbor ID is entered and the session stays in the DOWN state or never appears in the table.