[nsp] eBGP routes not balancing

[Gert Doering]

hi,

On Mon, Nov 17, 2003 at 02:59:02PM -0800, Steve Francis wrote:
> One way I've made the load balancing more equal in such situations is to 
> apply a route map to one of the peers, that says if the route learned is 
> for an IP in the range 0.0.0.0 through 128.255.255.255, it has a 
> local_pref of 90; everything else from that peer has a local_pref of 110.
> 
> The local_pref of the other peer will have the default of 100.

Doing that means your BGP setup could as well be replaced by two
half-default routes

  ip route 0.0.0.0 128.0.0.0 <isp1>
  ip route 128.0.0.0 128.0.0.0 <isp2>

as setting local-pref will override everything else, including (and most
important) path length...

So if ISP 1 is presenting you a veeeeeeeerrry long path to, say,
4.0.0.0/8, and ISP 2 has really top connectivity to that network, your
policy will still force out everything via ISP 1.

A more reasonable approach would be to achieve the same goal using MED
(and "bgp always-compare-med").  That way, the manual balancing will only
affect networks that you see over equal-length paths.

gert
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Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de