Query in BGP

Unanswered Question
Jun 14th, 2010
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Can be use same BGP AS number on different router but on same LAN.

Scenario: R1--65535 ---->    ISP 1 (AS)              

               R2--  ?     ----->    ISP2  (AS)

R1 and R2 Lan ip is in same LAN.

I want to advertise my same Lan in both ISP.....IS it possible?

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Chetan Kumar Ress Mon, 06/14/2010 - 08:26
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You question is not clear , Can you Describe this one clearly. Or else if below soluiton will help & match the senario then its ok.

Single AS can use on multiple router and it will create an IBGP neighbore.

To achive this you have to configure BGP neighbore using Loopback & those loopback should reach each other via IGP.

Below is the sample config

R2 (config) # int loopback 0

R2 (config-if) # ip add x.x.x.x x.x.x.x

R2 (config) # router bgp xxx

R2 (config-router) # neighbor x.x.x.x remote-as xxx

R2 (config-router) # neighbor x.x.x.x ebgp-Multihop x

R2 (config-router) # neighbor x.x.x.x update-source loopback 0


Chetan kumar

vishwancc Mon, 06/14/2010 - 10:42
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Hi Arjun ,

since your  question is not very clear my answer might not be the one you are looking for but anyways..

I guess u r saying that both the router are are in the same vlan and you want to use same AS number for both.

There is no problem you could use it.

But in your diagram you showed 2 different ISP , so my suggestion will be to have a public AS since you want your network to have visibility in the internet cloud.




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