Neighbor Requirements

The area number must match

Interfaces must be in the same subnet

OSPF process must not be shutdown

OSPF Router IDs must be unique

Hello and Dead timers must match

The authentication setting must match

IP MRU setting must match

Can become OSPF neighbors, but OSPF doesn't operate properly.

The OSPF Network Type must match

Can become OSPF neighbors, but OSPF doesn't operate properly.