[c-nsp] Load balancing outbound traffic with BGP

[oles at ovh.net]

On Tue, Feb 26, 2008 at 10:07:56PM +0100, Matyas Koszik wrote:
> 
> 
> You may want to try
> 
> bgp bestpath as-path multipath-relax

not available on 6509/sup720BXL

Router(config-router)#bgp bestpath ?
  compare-routerid  Compare router-id for identical EBGP paths
  cost-community    cost community
  med               MED attribute

> to achieve load-sharing accross the providers, with different (but equal
> length) as-paths. (Works for me like a charm in a situation similar to
> yours.)
> 
> 
> 
> 
> On Tue, 26 Feb 2008, Jeff Chan wrote:
> 
> > Hi All,
> > Given multiple, roughly equal upstreams (Sprint, ATT, Level3)
> > providing full BGP tables to a small ISP, what's the best way to
> > balance the outbound traffic?  The problem is that all else being
> > equal (path length, local pref, etc.) BGP decides to take the one with
> > the lowest peering IP address.  Given that the upstreams have
> > many/most of the same customers and peers, the peer with the lowest IP
> > address seems to win too often, meaning it does too much outbound
> > compared to the others.
> >
> > I asked the same question some time ago and the common practice answer
> > seemed to be prefer traffic for some other large networks (UUNet,
> > Qwest, AOL, etc.) over the peers with higher IP address.  Is this
> > still the case?  Seems kind of an ugly hack, but it works.
> >
> > Are there any other approaches?  How about jumbling up or staggering
> > the local preferences:
> >
> > ISP S:
> >
> > customers: localpref 120
> > peers:     localpref 110
> > others:    localpref 100
> >
> > ISP A:
> >
> > customers: localpref 110
> > peers:     localpref 100
> > others:    localpref  90
> >
> > ISP L:
> >
> > customers: localpref 100
> > peers:     localpref  90
> > others:    localpref  80
> >
> > Where S has the highest IP address, A next highest, L lowest.  Haven't
> > tried this; just a thought to try to compensate for the IP address
> > decision.
> >
> > Cheers,
> >
> > Jeff C.
> >
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> >
> 
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