In a previous lesson, I showed you how to configure the OSPF point-to-multipoint network type. This time we’ll look at the OSPF point-to-multipoint non-broadcast network type. It’s the same thing, but we’ll have to specify OSPF neighbors ourselves. Here is the topology that we’ll use:
There are a couple of things that you need to be aware of:
- No Automatic neighbor discovery, so you 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.
Here’s the configuration for the Hub router:
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 non-broadcast Hub(config-if)#exit Hub(config)#router ospf 1 Hub(config-router)#network 192.168.123.0 0.0.0.255 area 0 Hub(config-router)#neighbor 192.168.123.2 Hub(config-router)#neighbor 192.168.123.3
This is the hub configuration. I changed the network type to point-to-multipoint non-broadcast, advertised the 192.168.123.0 /24 network in OSPF, and, most important…specified the OSPF neighbors myself. Let’s look at the spoke router configuration: