Beginner's BGP route map question

CriscoSystems · ‎08-21-2008

I imagine this is a beginner's-calibre; bonk-me-over-the-head-with-a-saucepan-for-asking kind of question, but here it is anyway:

When I was troubleshooting my other BGP issue that y'all were so helpful with, I tried configuring a route-map to set the weight to 100 for incoming routes. I created a route-map named "Toby" (Toby is my nephew!) like this here:

Sethtek-G#conf term

Enter configuration commands, one per line. End with CNTL/Z.

Sethtek-G(config)#route-map Toby

Sethtek-G(config-route-map)#match next-hop 1

Sethtek-G(config-route-map)#set weight 100

Sethtek-G(config-route-map)#exit

Sethtek-G(config)#access-list 1 permit host 172.16.0.2

Sethtek-G(config)#router bgp 190

Sethtek-G(config-router)#neighbor 172.16.0.2 route-map Toby

% Incomplete command.

Sethtek-G(config-router)#neighbor 172.16.0.2 route-map Toby in

% "Toby" used as BGP inbound route-map, nexthop match not supported

Sethtek-G(config-router)#

Dumb question: Why is nexthop match not supported for INBOUND routes? Aren't those the only routes for which the next-hop attribute is even interesting?

Harold Ritter · ‎08-21-2008

Seth,

As the messages indicated, you can use the match next next-hop statement on an inbound bgp route-map. You don't really need the match statement as you probably want to set the weight for all updates coming from that neighbor.

You could also just do:

neighbor 172.16.0.2 weight 100

Regards,

Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
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CriscoSystems · ‎08-25-2008

Well no, the message indicated that you CAIN'T use the next-hop for an inbound route map, and I don't understand why.

In a multiaccess IBGP network, plenty of routes with different next-hops could be coming in from a single neighbor. And "probably" doesn't cut it, because if you want to adjust the weights on a per-route basis (isn't that the whole point of the weight attribute anyway), I don't see why you shouldn't be able to.