[nsp] eBGP routes not balancing

Streiner, Justin streiner at stargate.net
Mon Nov 17 22:24:01 EST 2003

On Mon, 17 Nov 2003, Jeff Chan wrote:

> After enabling "bgp bestpath compare-routerid" and resetting the
> sessions, most of the traffic went to the peer with the lower
> numerical address (ID), which again is unbalanced.  So I've
> disabled compare-routerid and will probably reset all the
> sessions late at night with "clear ip bgp all" in the hopes
> that the ages of the routes will then be close enough, since
> they're all cleared and re-learned at the same time, to
> result in traffic that is closer to balanced.

Unless you use a route-optimization tool (RouteScience, netVMG, others) as
other posters have mentioned, achieving 'perfect' balance with BGP will be
an uphill battle.  The above tools can be quite expensive.  It will also
be a continuous, manual, and imperfect process.  Tweak your BGP policies,
see what effect it has on your traffic.  Tweak again, watch again.  Wash,
rinse, repeat.

> Both providers are large, our pipes to them and routing tables
> learned similar sized, so balanced traffic should be a
> reasonable goal.  Any other suggestions are welcomed.  Aside
> from external route servers, how is anyone else dealing with
> this?  Balancing fully multi-homed traffic must be an issue
> for lots of folks....    Why can't IOS just do the right thing?
> :P

Many people put the resources (router, horsepower, transit bandwidth, etc)
where the traffic wants to go, and possibly only shape their transit
traffic in very broad strokes.  Large networks often make use of communities
and MEDs to assist in this process.


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