There are a couple of things that you need to be aware of:
- Automatic neighbor discovery so no need to configure OSPF neighbors yourself.
- No DR/BDR election since OSPF sees the network as a collection of point-to-point links.
- Only a single IP subnet is used in the topology above.
- Make sure your frame-relay network is configured with the broadcast keyword.
Let’s take a look at the configuration:
Hub(config)#interface serial 0/0 Hub(config-if)#ip address 192.168.123.1 255.255.255.0 Hub(config-if)#encapsulation frame-relay Hub(config-if)#ip ospf network point-to-multipoint Hub(config-if)#exit Hub(config)#router ospf 1 Hub(config-router)#network 192.168.123.0 0.0.0.255 area 0
This is the hub configuration. I changed the network type to point-to-multipoint and advertised the 192.168.123.0 /24 network in OSPF. Let’s look at the spoke router configuration: