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Loopback interface for security and testing

Posted on 2004-10-05
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Last Modified: 2008-03-06
I have perm router that I want to setup interface loopback0 command on.  If my internal is on 10.0.0.0/24 and my real ip's are 63.x.x.x can i setup my loopback interface to 172.16.x.x ?

What are the benefits ?
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Question by:cogit
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Expert Comment

by:PennGwyn
ID: 12232083
Yes, you can.

The main benefit is that you can swap around what networks/addresses are connected at this router, and still have a consistent address which identifies the device.

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by:cogit
ID: 12232212
Its a 1720 with one S0 and 1 E0
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JFrederick29 earned 2000 total points
ID: 12236418
The benefit is that the loopback interface never goes down.  The true benefit of a loopback address comes into play when running routing protocols like OSPF for specifying the OSPF router ID.  It's also crucial when you are running iBGP and have mutliple paths between iBGP peers.  Loopback interfaces can also be setup in a LAB environment to simulate connected networks that don't actually exist.

You can assign the loopback interface whichever address you like, remember to treat it like any other destination network, if you want to reach the loopback address from another router, you will need to setup static routes or redistribute it into your routing protocol.  If you don't have a specific need to use a loopback interface, don't bother setting one up.
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