[quagga-dev 7906] Re: [PATCH] bgpd: Implement multipath insertion into RIB

paul at jakma.org paul at jakma.org
Wed Apr 7 12:34:16 BST 2010

On Thu, 25 Mar 2010, Boian Bonev wrote:

> I have started implementing multipath support in bgpd. I have used 
> the cisco model and maximum-paths command in router context.
> The logic does not change announces to neighbours. It selects more
> than one path for insertion into the RIB.
> Testing with 4 full sessions and 'bgp bestpath as-path ignore' didn't
> show issues:
> ip r | grep -v nexthop | wc -l
> 318356
> ip r | grep nexthop | wc -l
> 1254548
> Maybe this code is not ready for inclusion without a review - your
> comments are welcome

To have this accepted you'd need to ensure that any re-advertisements 
of the route at least include all the ASNs in the AS-Path.

Basically, you'd need to generate an aggregate.

Note that other vendors do not enable multi-path by default, and my 
vague understanding is that multi-path enhancements which do not 
aggregate have a bad reputation in the general operator community 
precisely because they are open to routing loop problems.

Paul Jakma	paul at jakma.org	Key ID: 64A2FF6A
I used to get high on life but lately I've built up a resistance.

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