What is a Loopback interface and how to configure it
Loopback interfaces a common network topologi used by many vendors, not just cisco. After you’ve read this article you should be able to describe basics about Loopback interfaces and configure a loopback interface on a cisco router.
How to configure a Loopback interface on cisco router
The loopback interface is a virtual/logical interface on a router that will always stay up even if some hardware interface goes down it can still be accesable from another interface on the router, which makes it ideal in situations where routers need redundant ways to connect with each other, fx when configureing BGP Neighbors.
But there is a lot more scenarious where loopback interfaces are ideal like, mangament acces, redundant VPN connections.
How to configure a Loopback interface on cisco router
Step 1: Login to global configuration mode
# Type enable to enter Privileged EXEC mode
enable
# Type Configure Terminal to enter global configuration mode
configure terminalStep 2: Create loopback interface
A loopback interface on a cisco router is identified by a loopback ID which must be a unique number. Replace <0-???> with the desired number you want to use for your loopback interface.
Router(config)# interface loopback <0-???>Step 2: Assign an ip address to the interface
Treat the loopback interface allmost like a normal interface, configure it with an ip address aswell other options you might want.
Router(config-if)# ip address <ip-address> <subnet-mask>