Solved: Stop BGP==>RIB Updates?

PAUL TRIVINO · ‎05-11-2009

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

Harold Ritter · ‎05-12-2009

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

Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México

View solution in original post

Laurent Aubert · ‎05-11-2009

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 · ‎05-12-2009

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

Harold Ritter · ‎05-12-2009

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

Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México

PAUL TRIVINO · ‎05-13-2009

My "Default Administrative Distance" chart shows 255 as "Unknown," guess I'll have to update that. Thanks, worked a treat.

Paul