OSPF Network Types
Understanding OSPF Network types is bit tricky unless you don’t start from the concepts.
We have totally 5 different network types in Cisco Networks:
RFC Specific:
1. Non-Broadcast
2. Point to multipoint
Cisco Specific:
3. Point to Multipoint non-broadcast
4. Point to point
5. Broadcast
Non-Broadcast:
· Default Network type on Cisco routers.
· Routers cannot discover neighbors automatically, thus manual neighbors must be configured. (it is enough if you just configure on the Hub)
· Hellos are sent as Unicast.
· DR/BDR elections happen.
· Hub must be elected as DR as it has full connectivity to the spokes. And spokes cannot get elected as DR/BDR.
· Need to set the priority to 0 on the Spoke’s interface.
· Hello and Dead timers are 30/120
Point to Multipoint:
· Automatic neighbor discovery happens.
· Hellos are sent as Multicast
· No DR/BDR elections
· Hello and dead timers are 30/120.
Point to Multipoint Non-Broadcast:
· Routers cannot discover neighbors automatically, thus manual neighbors must be configured. (it is enough if you just configure on the Hub)
· Hellos are sent as Unicast.
· No DR/BDR elections.
· Hello and Dead timers are 30/120.
Point to point:
· Default on point to point sub-interfaces
· Neighbors are discovered automatically.
· Hellos are sent as Multicast.
· No DR/BDR elections
· Hello and Dead timers are 10/40
Broadcast:
· Neighbors are discovered automatically.
· Hellos are sent as multicast
· DR/BDR elections happen.
· Hello and Dead timers are 10/40
I will configure all these network types in a frame-relay network and post in my subsequent posts.
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