loopback interface

[CiscoGuy79]

Can someone gave a dumbed down version of a loopback interface and what it is used for?

I read up on it on cisco but it really didn't give me much

" You can specify a software-only interface called a loopback interface to emulate an interface. It is supported on all platforms. A loopback interface is a virtual interface that is always up and allows BGP and RSRB sessions to stay up even if the outbound interface is down.

You can use the loopback interface as the termination address for BGP sessions, for RSRB connections, or to establish a Telnet session from the device's console to its auxiliary port when all other interfaces are down. You can also use a loopback interface to configure IPX-PPP on asynchronous interfaces. To do so, you must associate an asynchronous interface with a loopback interface configured to run IPX. In applications where other routers or access servers attempt to reach this loopback interface, you should configure a routing protocol to distribute the subnet assigned to the loopback address."

That is what cisco said????

thanks,
nathan

 

[vipergg]

A loopback is used because it is always up and thus will create a stable environment when useing routing protocols like bgp or ospf. If you didn't have a loopback and you had mutliple routes out of the router and the router id was an interface that went down then you are sol , if you use a loopback that is always up it will find alternative routes out of the router .

 

[CiscoGuy79]

Thank you very much, so instead of having the RID be an interface that can go down and lose ospf you use a loopback interface.

hey thanks man that's exactly what i was looking for

nathan