Cisco Certified Network Associate (CCNA) Practice Exam

Which command applies OSPF configuration to the loopback interface in a network?

1. (config-if)#ip ospf PROCESS_NUMBER area AREA_NUMBER

2. (config)#interface lo0

3. (config)#router ospf PROCESS_NUMBER

4. (config-if)#ip ospf enable

The correct answer is: (config)#interface lo0

The correct command to apply OSPF configuration specifically to the loopback interface in a network is the command that references the interface directly, allowing you to enter interface configuration mode for the loopback interface. By entering the command to access the loopback interface, you prepare to define parameters like IP addressing and link OSPF configurations to that interface. This is crucial because OSPF considers the loopback interface as a potentially stable endpoint for routing purposes, optimizing overall routing design and stability. The command that involves OSPF process number and area configuration specifies how OSPF operates on an interface level but must be preceded by identifying the interface itself. While configuring OSPF on a specific interface is important, you first need to ensure you are addressing the correct interface where that OSPF configuration will apply. Accessing the loopback interface precedes applying any OSPF-related commands, aligning with standard practices for configuring OSPF effectively in a network environment.