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BGP Loopback Interfaces

Unanswered Question
Nov 16th, 2006
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If you use a loopback interface to peer Cisco routers using IBGP does your IGP have to advertise that loopback interface.


Any help will be rated.... i'm trying to learn BGP.


Thanks



Gavin

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mheusinger Thu, 11/16/2006 - 08:22
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Hi,


yes this is needed. BGP uses TCP (port 179) to setup a BGP session. If the IP address of the neighbor is not known from the routers IP routing table then the session never starts.

An IP of a Loopback interface will not be known by any other device without announcement through an IGP. The only alternative would be static routing between the loopbacks.


So for iBGP to start make sure your Loopback IPs are announced through your IGP.


Hope this helps! Please rate all posts.


Regards, Martin

gavinmckee Thu, 11/16/2006 - 08:25
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thanks Martin, I'm just beginning to learn this wonderful protocol :)


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