From: Nelson Salvatorelli (nsalvato@xxxxxxxxx)
Date: Mon Mar 25 2002 - 06:47:55 GMT-3
Hi Ying,
You have to also adjust the metrics from the IGP so you can have two
routes from the IGP with the same metric in R1.
Also making sure you have the same metrics for BGP and configuring 'bgp
bestpath ingnore as-path' and also 'maximum-paths 2'
For example, modify the cost of the link R1-R2 accordingly that would be
equivalent to the sum of R2-R3-R1. Remember that one of the tie-breakers
in the BGP decision algorithm is the IGP metric.
Wrt BGP and multiple paths, you're right, BGP if configured as default
will always select from his table one path and promote it to the Routing
Table. If all things are equal, then the tie-breaker is the route with
higher next-hop router id... But, but, but, if you configure
'maximum-paths 2' for eBGP, having all things equal, even your IGP
metric, BGP will select two routes from it's table and promote them to
the Routing Table.... Therefore it will load balance.
If you can, try it and let me know. I will try it as well when I have
time!
Cheers,
-nelson
> -----Original Message-----
> From: ying chang [mailto:ying_c@hotmail.com]
> Sent: 25 March 2002 02:11
> To: Nelson Salvatorelli; ccielab@groupstudy.com
> Subject: RE: bgp load balancing
>
>
> Hi Nelson,
>
> Not only do we have to adjust the metrics, the administrative
> distance also
> needs to be adjusted as well so we can have two equal paths.
>
> "maximum-paths 2" is needed, but after thinking it over, I
> don't think "bgp
> bestpath as-path ignore" will help. Even if we ignore the
> as-path, the bgp
> selection process will have other tie-breakers to select the
> best path, so
> there will be only one path after the selection process,
> instead of the two
> paths that we would like. Please correct me if I'm wrong. I'm
> not sure if
> static route is the only choice for this question, but that's
> what I can
> come up with and that works for now.
>
> Thanks,
> Chang
>
> >From: "Nelson Salvatorelli" <nsalvato@cisco.com>
> >To: "ying chang" <ying_c@hotmail.com>, <ccielab@groupstudy.com>
> >Subject: RE: bgp load balancing
> >Date: Mon, 25 Mar 2002 01:27:27 -0000
> >
> >Hi,
> >
> >Not only you have to configure 'bgp bestpath as-path ignore'
> but also
> >'maximum-paths 2'. The latter if used in iBGP, will only be
> available
> >from 12.2S. 12.2S is not out yet. In your case should work
> since it is
> >eBGP... And multipath support is available for eBGP since 11.3 If I
> >remember correctly.
> >
> >It's worth a try in the lab... I guess if you adjust the metrics
> >accordingly (to make them all equal) and ignore the AS_PATH
> attr, then
> >it should work nicely...
> >
> >Good question!
> >Cheers,
> >
> >-nelson
> >
> >
> > > -----Original Message-----
> > > From: ying chang [mailto:ying_c@hotmail.com]
> > > Sent: 25 March 2002 00:52
> > > To: ccielab@groupstudy.com
> > > Subject: Re: bgp load balancing
> > >
> > >
> > > Hi,
> > >
> > > Well, "bgp bestpath as-path ignore" is not available on
> my routers
> > > (IOS 12.1.11, 12.1.12, 12.0.20) even Cisco's CDROM said it was
> > > introduced in
> > > 12.0. So, is it still possible to use the direct link along
> > > with a transit
> > > AS to do load balancing?
> > >
> > > Thanks,
> > > Chang
> > >
> > >
> > > >From: "ying chang" <ying_c@hotmail.com>
> > > >Reply-To: "ying chang" <ying_c@hotmail.com>
> > > >To: ccielab@groupstudy.com
> > > >Subject: bgp load balancing
> > > >Date: Sun, 24 Mar 2002 19:23:14 -0500
> > > >
> > > >Hi,
> > > >
> > > >Can we load balancing R1 and R2 traffic using both R1-R2 and
> > > >R1-R3-R2 links? My thought is if we ignore as-path then R1-R3-R2
> > > >path should
> > > be as good as
> > > >R1-R2 path, but I'm not 100% sure.
> > > >
> > > > R1 (AS1, net 1.0.0.0)
> > > > / \
> > > > / \
> > > > / \
> > > > R2-----R3 (AS3, net 3.0.0.0)
> > > > (AS2, net 2.0.0.0)
> > > >
> > > >Thanks,
> > > >Chang
> > > >
> > > >
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