Cisco Certified Network Associate (CCNA) Practice Exam

What is used to create a loopback interface on an OSPF router?

1. interface loopback0

2. interface loopback1

3. interface loopback

4. interface ospfloop

The correct answer is: interface loopback0

Creating a loopback interface on an OSPF router involves using a specific command syntax that designates the loopback interface. The command "interface loopback0" is commonly used to create a loopback interface in Cisco IOS. The "0" indicates the specific identifier for this particular loopback interface, which allows for multiple loopback interfaces to be created on the same router by incrementing the interface number (e.g., loopback1, loopback2, etc.). Loopback interfaces are virtual interfaces that are always up and can be used for various testing and routing functions without relying on physical hardware. They play a crucial role in OSPF as they provide a stable endpoint that remains consistent regardless of changes in physical network conditions, ensuring reliable routing updates and neighbor relationships. Other options presented do not align with standard Cisco IOS syntax for loopback interface creation. Using "interface loopback" does not specify an interface number and, therefore, is incomplete. "interface loopback1" is technically a valid command but would refer to a different loopback interface rather than the traditional loopback0. "interface ospfloop" is not a recognized command in Cisco IOS for creating loopback interfaces. Therefore, the correct and standard command for creating a loop