Loopback interfaces

[lobo66]

hello all

could someone give me a good explination of why we use loopback interfaces and what they are for, also in what situation would a loopback int be used.

thx...

 

[KSM]

1. It is virtual interface, NOT physical like ethernet or serial.
2. It is always UP by default.
3. It is useful for SNMP management purpose and telneting to device.

 

[tcvander]

In addition to the above, Cisco will use the loopback address as the Router ID in OSPF Todd VanDerwerken, CCNA, CCDA
Technical Consultant

http://www.ciscolinks.net

"If at first you don't succeed...then sky diving isn't for you!"

 

[rcasta]

And I use is for BGP balancing purposes, since I have 4 T1 with my ISP, we set bgp peering by means of a loopback, so the router will fwd packets thru the 4 T1s since it knows peer address by all these links.

cheers

 

[firedragon]

loopbacks are also a good interface to ping and telnet to, becouse it is always up. so you always find a way to the router, if there is one.

 

[netlife]

Hi lobo,

The loopback interfaces are simply software interfaces.
The interfaces are configured for some cases in addition to
the reason explained by our friends.
For example, If ur router is running OSPF,then in that
case if u required to reboot ur router then during bootup it will search for atleast one active interface if it doesnt find that it will give error & wont be up.In this case active interface will play important role as it will be up during bootup as well.

Hope this will help u.

Cheers,

Netlife.