[c-nsp] BGP Route Selection

David Coulson david at davidcoulson.net
Wed Sep 10 09:59:12 EDT 2008


You could fix it with a route-map and as-path.

ip as-path access-list 98 permit ^3356$

route-map as-3356-inbound permit 5
 match as-path 98
 set local-preference 200

Then in the router bgp section, add this:

neighbour 4.53.194.5 route-map as-3356-inbound in

This will solve the problem for the specific route, however it may not 
do what you intend with all of the routes on your network.

David


Gregory Boehnlein wrote:
> Cisco RSP4+ (R5000) processor with 262144K/2072K bytes of memory. Slave in
> slot 3 is running Cisco IOS Software, RSP Software (RSP-IK91SV-M), Version
> 12.2(25)S12, RELEASE SOFTWARE (fc1)
>
> Hello,
> 	I'm bringing up a new BGP peer and am working at tweaking our BGP
> routing configuration. In doing so, I'm noticing something weird about a
> particular path, and since I'm rather tired at the moment, wanted to have a
> fresh set of eyes take a look at it. Can someone explain to me the reason
> why Path #3 is being chosen over the lower AS-Path #1 and #2 routing
> choices?
>
> core1#show ip bgp 4.68.95.11
> BGP routing table entry for 4.0.0.0/9, version 6
> Paths: (4 available, best #3, table Default-IP-Routing-Table)
> Multipath: eBGP
>   Not advertised to any peer
>   3356, (aggregated by 3356 4.69.130.12)
>     4.53.194.5 from 4.53.194.5 (4.69.181.195)
>       Origin IGP, metric 1000, localpref 100, valid, external,
> atomic-aggregate
>       Community: 3356:0 3356:3 3356:100 3356:123 3356:575 3356:2006
>   3356, (aggregated by 3356 4.69.130.12), (received-only)
>     4.53.194.5 from 4.53.194.5 (4.69.181.195)
>       Origin IGP, metric 0, localpref 100, valid, external, atomic-aggregate
>       Community: 3356:0 3356:3 3356:100 3356:123 3356:575 3356:2006
>   2828 3356, (aggregated by 3356 4.69.130.12)
>     67.106.93.233 (metric 20) from 207.166.219.2 (207.166.219.2)
>       Origin IGP, metric 1000, localpref 150, valid, internal,
> atomic-aggregate, best
>   2828 3356, (aggregated by 3356 4.69.130.12), (received-only)
>     67.106.93.233 (metric 20) from 207.166.219.2 (207.166.219.2)
>       Origin IGP, metric 3, localpref 150, valid, internal, atomic-aggregate
>
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