Which command can be used to configure OSPF on a router?

The command to configure OSPF on a router is "router ospf [process-id]." This command is fundamental in enabling the Open Shortest Path First (OSPF) routing protocol on a Cisco router.

When you enter this command in the global configuration mode, you initiate the OSPF routing process, where 'process-id' serves as a unique identifier for that specific OSPF instance. This allows the router to manage multiple OSPF routing instances simultaneously if needed. The process ID is locally significant and does not have to match the process IDs of other routers within the same OSPF area or autonomous system.

Using this command, network administrators can then proceed to configure the OSPF parameters, including network statements, area assignments, and other related settings essential for the OSPF operation. This makes it a crucial step in establishing OSPF on a router and ensuring proper routing within an IP network.