Re: [nsp] OSPF load-balance

From: Rick Burts (burts@mentortech.com)
Date: Thu Sep 07 2000 - 00:48:08 EDT


Paul

OSPF will load balance only when it believes that the links do have equal
cost. You can achieve load balancing over un-equal links by misleading
OSPF (lie to it). You could achieve this by creative altering of the
bandwidth or (better approach) by setting the OSPF cost on the links to
be the same.

Although you can achieve load balancing over un-equal links, this is
usually not a good thing to do. Since you have supplied incorrect
information to OSPF, some of its routing decisions will not be optimum,
and you might not be so happey with the total results.

I would suggest a different alternative. If you are attempting to
achieve utilization of different speed links, I would suggest that
you look at the possibility of policy routing. Let OSPF send most
of your traffic on the "best" link and use policy routing to identify
certain types of traffic and have that traffic sent over the slower
link. Since you are identifying the traffic types, you should be
able to achieve the kind of utilization that you may be seeking.

Rick

On Wed, 6 Sep 2000 paulp@mozcom.com wrote:

> Hi,
> I would like to have your suggestions on the following issue.
> OSPF can load balance between links with equal cost, but is there a way to
> effectively load balance two unequal cost links w/o oversubscribing
> higher cost link?
>
> Cheers,
>
> Paul P. Pongco
> Mosaic Communications, Inc.
>

Rick Burts, CCSI CCIE 4615 burts@mentortech.com
Mentor Technologies 410-280-8840 ex 3015
275 West Street 410-280-8859 fax
Plaza 70
Annapolis, Md 21401

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