Importance of Loopback Interface

[kpatoli]

What is the importance of loopback interface?

And under what circumstances it is necessary or rather must to have loopback interface configured?

[rsissons]

The advantage of coding a loopback interface is that it enables you to have an IP address on the router which is always up rather than being dependant on the physical interface being up.

This is important when running something like OSPF which requires an IP address on the router as the router id. It is not required to use loopback addresses but it is STRONGLY recommended!

[rpoorman]

Hi..

Back to this loopback conversation. I have a 7204VXR that we set up and would like to employ the loopback interface, however I am not sure how to IP it. If I use an IP that is on the same network as the primary Ethernet interface it won't bind. So do I set the loopback as the primary IP for the entire router then do unnumbered on the ethernet as well? There is little documentation or examples and many of them show the ethernet and loopback with different addresses. We are running multiple T1's and are getting ready to deploy an ATM DS-3. We want to be able to have unnumbered on all the serial ports..

Thanks,

Ray