What OSPF command is used to configure the router ID?

The command used to configure the router ID in OSPF is "router-id [id]". This command is entered in the OSPF router configuration mode and is essential for identifying the OSPF router within an OSPF network.

The router ID is a 32-bit value typically represented in the same format as an IPv4 address. It serves as a unique identifier for each router participating in the OSPF process, which is crucial for maintaining OSPF neighbor relationships and network topology information. By setting the router ID explicitly, network administrators can ensure consistent identification, especially in scenarios where the router could have multiple interfaces with IP addresses.

The other options presented are not valid commands for configuring the router ID in OSPF. For example, "ospf router-id [id]" and "interface router-id [id]" are not recognized syntactical structures in the Cisco IOS for configuring OSPF parameters. Additionally, "set router-id [id]" is not an appropriate command within the OSPF configuration context. Thus, the specified option is the correct choice for accurately configuring the router ID.