Configuration

The OSPF process ID is locally significant. Routers with different process IDs can become OSPF neighbors.

The OSPF network command requires you to specify the area.

The network command tells OSPF to:

• look for any interfaces with an IP address contained in the range specified in the network command.

• activate OSPF on the interface in the specified area.

• try to become OSPF neighbors with other OSPF-activated neighbor routers.

Passive-interface

R1(config-router)# passive-interface g2/0

The passive-interface command tells the router to stop sending OSPF 'hello' messages out of the interface.

However, the router will continue to send LSAs informing its neighbors about the subnet configured on the interface.

You should always use this command on interfaces that don't have any OSPF neighbors.

Advertise Default Routes

R1(config-router)# default-information originate

Show

Router ID order of priority:

1. Manual configuration.

2. The highest IP address on a loopback interface.

3. The highest IP address on a physical interface.

An autonomous system boundary router (ASBR) is an OSPF router that connects the OSPF network to an external network.

R1 is connected to the internet. By using the default-information originate command, R1 becomes an ASBR.