[c-nsp] BGP load balancing (outbound)

[Randy McAnally]

I can find very little info on 'bgp bestpath as-path multipath-relax'

Is this per-packet, or per-flow load balancing?

How much memory usage would it increase assuming 2-3 full tables in memory
already (around 400Mb usage, 1Gb RAM)?  Looks like you've got 2 defaults only.

--
Randy

---------- Original Message -----------
From: Andrew Tolstykh <andrew at atfam.com>
To: amps <djamps at gmail.com>
Cc: cisco-nsp at puck.nether.net
Sent: Tue, 18 May 2010 16:29:52 +1000
Subject: Re: [c-nsp] BGP load balancing (outbound)

> ECMP load balancing works with the hidden "bgp bestpath as-path 
> multipath-relax" command applied (thanks Anton!)
> 
> router bgp XXX
> maximum-paths 2
> bgp bestpath as-path multipath-relax
> 
> sh ip route bgp
> B*    0.0.0.0/0 [20/0] via 13.13.13.3, 00:05:59
>                 [20/0] via 12.12.12.2, 00:05:59
> 
> sho ip cef 0.0.0.0 0.0.0.0
> 0.0.0.0/0
>   nexthop 12.12.12.2 FastEthernet1/0
>   nexthop 13.13.13.3 FastEthernet1/1
> 
> If you are after the per-AS load-sharing configuration, then you 
> should probably flip route-map TRANSIT-1-INT permit 10 and 20 statements.
> Also don't forget to add blank "route-map TRANSIT-2-IN permit 20" statement.
> 
> route-map TRANSIT-1-IN permit 10
> match as-path 105
> set local-preference 210
> route-map TRANSIT-1-IN permit 20
> 
> route-map TRANSIT-2-IN permit 10
> match as-path 106
> set local-preference 210
> route-map TRANSIT-2-IN permit 20
> 
> HTH,
> Andrew
> 
> On 18/05/2010, at 2:42 AM, amps wrote:
> 
> > Let's say I wanted to send traffic to even AS's out peer 1 and odd AS's
out peer 2.
> > 
> > Am I crazy?  (Seems better than using metrics based solely on static IP
ranges...)
> > 
> > Would this work?
> > 
> > route-map TRANSIT-1-IN permit 10
> >  set as-path prepend last-as 1
> > !
> > route-map TRANSIT-1-IN permit 20
> >  match as-path 105
> >  set local-preference 210
> > !
> > 
> > route-map TRANSIT-2-OUT permit 10
> >  set as-path prepend xxxxx
> > !
> > 
> > route-map TRANSIT-2-IN permit 10
> >  match as-path 106
> >  set local-preference 210
> > !
> > 
> > route-map TRANSIT-2-OUT permit 10
> > !
> > 
> > ip as-path access-list 105 permit [02468]$
> > 
> > ip as-path access-list 106 permit [13579]$
> > 
> > 
> > On Mon, May 17, 2010 at 10:59 AM, Anton Kapela <tkapela at gmail.com> wrote:
> > On Mon, May 17, 2010 at 10:42 AM, Andrew Tolstykh <andrew at atfam.com> wrote:
> > > Just a shot in the dark, but I don't see load balancing enabled in your
configuration snippet:
> > >
> > > router bgp xxxxx
> > 
> > This question comes up semi-often, perhaps there ought to be a FAQ? (I
> > may have missed it).
> > 
> > For different-upstream AS's, ecmp will not normally occur. You'll need
> > to adjust the bgp bestpath determination functions, else the different
> > next-AS's will prevent ECMP forwarding from being pushed to the FIB.
> > 
> > http://puck.nether.net/pipermail/cisco-nsp/2005-November/025993.html
> > 
> > -Tk
> >
> 
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------- End of Original Message -------