Load Balancing based on circuit Utilization?

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Jan 20th, 2009
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Hello all,

I searched the threads but did not see anything on this.

---anyway this is my question. ---

I want to be able to do per detination load balancing based on link utilization. Say if a link becomes 80% saturated. Then a mechnism will kick in based on a thresold and I can route additional traffic over a diffrent link


I have a backbone of a bunch of 7200 vxr's. with DS3's running between them. we are running ospf and mpls.



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Giuseppe Larosa Tue, 01/20/2009 - 11:11
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Hello John,

in DDR the dialer load-threshold and the backup command have parameters for doing something like that.

However, in your case I suppose you don't pay DS3 links based on usage.

So you can use up to 4 parallel paths by default with OSPF and you can increase it up to 8 in modern IOS versions.

router ospf 10

maximum-paths 8

also because a backup link is kept down so no routing protocol information can be used.

If you are using MPLS you can consider to use MPLS TE to move some traffic quotas over MPLS TE tunnels so that you can use also the links that are not on the shortest path.

Hope to help


jglobermudez Tue, 01/20/2009 - 11:42
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Thanks for the reply. But I am not looking to load balance all of the time, only when needed.

I am looking for a technology that uses a triggering / threshold mechanism. the reason is all traffic is Delay sensitive VOIP traffic. Does cisco have any technology that ca do this?

Also I attached a crude Viseo of a network.

let say in the viseo I am sending most traffic over link A, How can I start send over link b , on when link a reaches 80% utilization. I do not want to load balance over link b at all times. because of time delays.

thanks for your time,


Joseph W. Doherty Tue, 01/20/2009 - 16:34
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A Cisco technology that might support what you desire is OER/PfR. However, at the moment it doesn't support OSPF; just BGP or static routing.

jglobermudez Thu, 01/22/2009 - 22:11
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can you point me to configs on hiw to set this up in an enterprise no ebgp



Joseph W. Doherty Fri, 01/23/2009 - 04:21
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You might start here: http://www.cisco.com/en/US/products/ps8787/products_ios_protocol_option_home.html

Detail command information can be found within the IOS reference manuals and configuration guides.

Additional infomation can be found search the Cisco site using terms "OER" or "PFR".


BTW: Believe you'll need to be runing 12.3T or later and might require one of the advanced IOS feature sets.


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