Stop BGP==>RIB Updates?

Answered Question
May 11th, 2009
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I am building a router as a route server ONLY, i.e. it peers with all of our other BGP routers (outside the network, colo's mostly). But it will only ever send BGP updates for things like RTBH. (And we're not ready for that yet, anyway).


I have a 2811 I have configured for this purpose. And this works, but it keeps the 2811 very busy. What I've noticed is that BGP has about half the CPU time and 'IP RIB Update' has most of the rest.


Does anyone know of a way to stop the router from even TRYING to update the route table? I only need this route info in BGP, it won't ever be used for 'routing.'


TIA.


Paul

Correct Answer by Harold Ritter about 7 years 10 months ago

Paul,


You could set the AD to 255 under the BGP process so that routes would be received, selected as best paths and advertised to BGP neighbors if need be but they would never be installed in the RIB because AD 255 tells IOS not to install the route in the RIB.


Regards

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Laurent Aubert Mon, 05/11/2009 - 17:17
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Hi Paul,


Your 2811 should peer only with your RR to limit the number of peering.


Also you can deny all the received BGP updates as you don't need them at all. The purpose is just to send an update usually from a route pointing to null 0.


HTH


Laurent.

cpubob Tue, 05/12/2009 - 06:46
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Since you want the routes in BGP but not in the routing table, you should just make them invalid as they are recieved. The easiest way I can think to do this is to set the next-hop to some unreachable address. Something like this:


route-map invalidate permit 10

set ip next-hop 1.1.1.1

!

router bgp xxxx

neighbor y.y.y.y route-map invalidate in

!


HTH,


-Rob

Correct Answer
Harold Ritter Tue, 05/12/2009 - 13:49
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Paul,


You could set the AD to 255 under the BGP process so that routes would be received, selected as best paths and advertised to BGP neighbors if need be but they would never be installed in the RIB because AD 255 tells IOS not to install the route in the RIB.


Regards

PAUL TRIVINO Wed, 05/13/2009 - 08:20
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My "Default Administrative Distance" chart shows 255 as "Unknown," guess I'll have to update that. Thanks, worked a treat.


Paul

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