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BGP Redistribute a more specific route

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Jun 14th, 2006
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Hi I have a scenario where WANA has a BGP process running to redistribute specific routes to a remote router WANB. WANA also has an EIGRP process that is learning intranet routes majority of which are summarised, as an example 192.168.0.0/16. WANB only needs to know about 192.168.1.0/24 rather than the whole 192.168.0.0/16 and to try and maintain some security I would like to only redistribute the /24 if possible. I've heard that this is not possible since WANA is only aware of the /16 - is there anyway around this?


Thanks.

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Richard Burts Wed, 06/14/2006 - 05:23
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Shaun


If WANA is going to advertise 192.168.1.0/24 via BGP to a peer router, then that prefix (address and mask) must appear in the local routing table. If WANA does not have that prefix in the local routing table then BGP can not advertise the route. If that route does not appear in the table normally (because WANA is learning a summarized set of routes) then you must put that prefix into the routing table. The most common way to do this would be a static route:

ip route 192.168.1.0 255.255.255.0

and then put a network statement into BGP for that prefix. You would not redistribute that static into your interior routing protocol. The route will be in the routing table, BGP will advertise it to the peer, and if any packets for that network are received at WANA it will forward toward the destination.


HTH


Rick

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