What command is used to configure OSPF on a router?

The command used to configure OSPF on a router is "router ospf [process-id]." When this command is entered in the global configuration mode of a Cisco router, it initiates the process of configuring OSPF (Open Shortest Path First) for a particular routing process identified by the process ID specified in the command. This process ID can be any number from 1 to 65535 and serves as a unique identifier for the OSPF process running on that router.

Once the command is executed, the router enters OSPF configuration mode, where additional commands can be applied to define network statements, set OSPF router parameters, configure OSPF authentication, and modify other OSPF characteristics. This command is essential for enabling OSPF functionality on a router and is the foundation for OSPF configuration in a Cisco networking environment.