Two routers on the same Ethernet VLAN show OSPF neighbor state stuck at 2-way. Router A's interface uses the default broadcast network type; Router B's interface is configured with 'ip ospf network point-to-point'. What is the most likely cause?

The OSPF neighbor state is stuck at 2-way because of an OSPF network type mismatch. Router A's interface is using the default broadcast network type, which expects a Designated Router (DR) and Backup Designated Router (BDR) election. Router B's interface is configured as point-to-point, which does not elect a DR/BDR. These differing expectations prevent the routers from fully establishing adjacency. An Area ID mismatch would prevent any neighbor relationship from forming. Authentication type mismatch would also prevent adjacency from forming beyond the ExStart state, typically. Differing dead interval timers would prevent adjacency from forming at all, not just getting stuck at 2-way.