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Interface loopback

aljugan

Hellow friends
Hope all of you will be fine..i have 1 question about interface loopback ..what is this and what is use of it and how can we configure it .
Thanks a lot

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Comments

NetworkVeteran

aljugan wrote: »

i have 1 question about interface loopback ..what is this and what is use of it and how can we configure it .

That's three questions!

1. It's a logical interface rather than a physical one.
2. It's always up so long as the router is, and thus a good address to use as a router ID or TCP endpoint.
3. You type "config" and then "int loopback #" to configure the interface.

blueberries

Like NetworkVeteran said, its a logical interface. It has too many uses to write about here, but it will be very important when you study OSPF and BGP.

If you want to try one out and verify it, simply do this:

(config): int loopback0
(config-if): ip address 1.1.1.1 255.255.255.255
*end

#: ping 1.1.1.1
....
#:sh ip int loopback0

aljugan

Thanks both of you for kind reply

Vask3n

When using GNS3 or Packet Tracer I will usually give my router a loopback address for telnetting purposes. I could get the same result by going into the config, going into an interface, setting the IP address, and doing a no shut, but it's a bit faster through loopback cause you don't have to perform a no shut (like NetworkVeteran said, it's always up)