Re: Load Balancing Multiple DS3s (outgoing) on a 7500

[Nick Feamster <feamster () lcs mit edu>]

On Sat, Mar 13, 2004 at 04:19:40PM -0800, Will Yardley wrote:
> On Fri, Mar 12, 2004 at 11:37:25PM -0500, Joe Abley wrote:
> > On 12 Mar 2004, at 23:24, joe mcguckin wrote:
> >
> > > I suspect that each FE goes to a different AS...
> >
> > In that case, sample/count outbound traffic volumes by 
> > (prefix/AS/AS_PATH/something), sort the resulting list, and develop an 
> > import policy based on the top N entries which shares the traffic by 
> > tweaking some other attribute to avoid the last-resort tie-break.
>
> The tool "ehnt" is pretty useful for generating a "top" style list of
> ASes in order of the amount of traffic you're sending their way.
>
> By the way, w/r/t to the tiebreaker stuff, note that (on Cisco devices)
> if you don't have "bgp bestpath compare-routerid" set, the route that
> was received first will be preferred. This minimizes route-flap, but can
> cause weird shifts in your traffic patterns when one bgp session or
> another goes down (credit goes to Mark Nagel for figuring out this one
> for me).
Also, check out:

http://www.nanog.org/mtg-0206/feamster.html

for some general guidelines, pitfalls, etc.  (The paper linked from the
presentation recently appeared in ACM Sigcomm CCR.)

-Nick