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BGP advertisment Question

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Sep 7th, 2006
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Lets say I have a Network range 192.168.1.0 /24. I have Two routers the Outside Edge Router#1 which would be 192.168.1.254/30 that connect to another router #2 192.168.1.253 /30. Is it possible to advertise 192.168.1.0 /24 in router #2 to my ISP using BGP. In order for Router #2 to talk to the ISP it needs to pass through router #1.

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sundar.palaniappan Thu, 09/07/2006 - 11:55
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Hi,


Yes, you can if you have a BGP peer between Router_2 and the ISP. BGP neighbor relationship can be multihop and it shouldn't be a problem.


HTH


Sundar

royalblues Fri, 09/08/2006 - 06:22
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All you need is layer 3 connectivity between your BGP peers.

IF the BGP peer in not connected directly, use the Multihop command to identify how many hops away your neighbor is


router bgp 64521

neighbor x.x.x.x remote-as

neighbor x.x.x.x ebgp-multihop 3


regards

Narayan

pduleski Fri, 09/08/2006 - 09:42
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Multi-hop isnt the problem, its the advertisment. We have two networks, 192.168.1.0/24 and 10.1.1.0/24: Router 1 does not run BGP, Router 2 does. The ISP recieved BGP advertisements from router 2 for 10.1.1.0/24, but not for 192.168.1.0/24. I am wondering if this is because to get to the BGP neighbor at the ISP, Router 2 needs to send the advertisement through an interface in the 192.168.1.0 network.


sundar.palaniappan Fri, 09/08/2006 - 09:57
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That shouldn't be a problem.


You need to have a route for 192.168.1.0/24 in your routing table for BGP to advertise this network. Your link between the Router 1 and Router 2 is 192.168.1.252/30. If you want to advertise this network then you need a config like this one.


router bgp xxx

network 192.168.1.252 mask 255.255.255.252


Hope this helps!


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