Re: [nsp] OSPF load balancing

From: Jon 'tex' Boone (tex@delamancha.org)
Date: Mon Dec 10 2001 - 13:09:19 EST


Nick <nick@arc.net.my> writes:

>+------------------+
>| Upstream |
>| Provider |
>+------------------+
> / \
> / \
> BR1 BR2
> \ /
> \ /
> \ /
> AR1
>
> BR1, BR2 and AR1 are internally running OSPF. BR1 and BR2 are running eBGP
> with the same upstream provider router. Assuming equal costs path for the
> AR1-BR1-UPSTREAM and AR1-BR2-UPSTREAM paths, will the two paths load balance
> or will only one path be preferred over the other? e.g. the path to the
> router with the highest router ID is preferred and the second path only used
> when the first path fails.

Nick,

    Is it the case that AR1 is running BGP? Or are you doing some form
  of redistribution into OSPF?

    If you are depending on iBGP to communicate the paths from the
  upstream, then you need to enable BGP multi-path (2).

    From the form of your question, I am assuming that you are
  redistributing into OSPF (which is not a great idea, although it may
  be necessary). In that case, we need to know if they are E1 or E2
  type routes. In any case, assuming that the appropriate costs are
  equal, AR1 will load-balance across paths.

-jon

-- 
------------------
Jon Allen Boone
tex@delamancha.org
CCIE #8338



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