[nsp] BGP question

[Jeff Chan]

On Thursday, September 11, 2003, 10:28:06 PM, Kevin Kevin wrote:
> I'm still a newbie at bgp, so please bear with me.
> I have two links to the internet. 
> A lot of routes from both providers have equal AS paths.
> If one bgp session gets reset all that traffic (the equal AS path
> routes) goes out to provider2 and does'nt reset back to provider1,
> providing that the bgp session to provider1 was the first one to come
> up. I don't have any metrics, weights or localpref on any routes.
> Is there any way to have those equal path routes default to provider1
> rather than provider2 if provider1's link and bgp session are up?
> Right now in order to reset those routes back to provider1 I have to do
> a hard "clear ip bgp provider2" reset. 

Hi Kevin,
I'd recommend stamping explicit metrics and localprefs on all the
incoming routes via a route map statement, even if the particular
values stamped are identical and happen to be the same as the
default ones.  If the values are all identical and the path
lengths are the same, then the routing should automatically
balance out when the other line comes back up.

Probably what's happening is that your router is inheriting
some of these values from your peers resulting in a precedence
that is not immediately obvious.  (However they should be
apparent if you look at the routing tables with a "show ip bgp".)
If any of the values are different, the values are probably
coming in from one of your peers.  That can happen when you don't
have a route map to reset them all to some nominal values.

Hope this helps,

Jeff C.
-- 
Jeff Chan
mailto:cisco-nsp at jeffchan.com
http://www.supranet.net/