Configuring OSPF for NBMA Networks

You can configure OSPF nonbroadcast multiaccess (NBMA) networks. You can configure your OSPF network type as NBMA, regardless of the default medium. This configuration is useful when, for example, you have routers in your network that do not support multicast addressing.

You must use the neighbor command to specify the router’s OSPF neighbors.

To configure OSPF for an NBMA network:

1. Configure an interface network type as NBMA for OSPF.

   host1(config-subif)#ip ospf network non-broadcast

2. Exit Interface Configuration mode. Enter Global Configuration mode.

   host1(config-subif)#exit

3. Configure an OSPF routing process, and enter Router Configuration mode.

   host1(config)#router ospf 5

4. Specify an OSPF neighbor, and optionally assign a priority number or poll interval to the neighbor.

   host1(config-router)#neighbor 10.12.14.1 priority 5 poll-interval 180

5. Repeat Step 4 for each neighbor in the OSPF network.

If you want to configure the network type for a specific interface or OSPF area, rather than for all OSPF interfaces, you can use the address network command rather than the ip ospf network command.

address network

• Use to configure the network type on a specific OSPF interface or for a specific OSPF area to a type other than the default for the medium.
• You must first issue the address area command before issuing the address network command.
• Example

  host1(config-router)#address 10.12.10.2 network broadcast

• Use the no version to restore the default value for the medium.
• See address network

ip ospf network

• Use to configure the network type on all OSPF interfaces on the OSPF network to a type other than the default for the medium.
• Example

  host1(config-if)#ip ospf network broadcast

• Use the no version to restore the default value for the medium.
• See ip ospf network

neighbor

• Use to configure OSPF neighbors on the NBMA network.
• Specify priority and poll interval only for routers that are eligible to become the designated router or backup designated router—that is, a router with a nonzero router priority value. The default priority value is 0, and the default polling interval is 120 seconds.
• Example

  host1(config-router)#neighbor 10.12.11.5 priority 100
  

• Use the no version to remove the neighbor or restore the default values 0 and 120.
• See neighbor

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