By adjusting the hello/dead timers you can make non-compatible OSPF network types appear as neighbors via the “show ip ospf neighbor” but they won’t become “adjacent” with each other. OSPF network types that use a DR (broadcast and non-broadcast) can neighbor with each other and function properly. Likewise OSPF network types (point-to-point and point-to-multipoint) that do not use a DR can neighbor with each other and function properly. But if you mix DR types with non-DR types they will not function properly (i.e. not fully adjacent). You should see in the OSPF database “Adv Router is not-reachable” messages when you’ve mixed DR and non-DR types.
Hereis what will work:
Broadcast to Broadcast
Non-Broadcastto Non-Broadcast
Point-to-Point to Point-to-Point
Point-to-Multipointto Point-to-Multipoint
Broadcast to Non-Broadcast (adjust hello/dead timers)
Point-to-Pointto Point-to-Multipoint (adjust hello/dead timers)
