EIGRP Load Balance

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Feb 24th, 2009
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I have two layer 3 devices that are connected to a switch via trunk. Both devices are configured with EIGRP routing. Device 1 as a metro e connection to the corporate and the device 2 are connected to the MPLS cloud. I would like to set EIGRP to make device 1 the primary route. If device 1 failed, all traffic will be follow to device 2. How can I make this work? Your help is greatly appreciated.


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Mohamed Sobair Tue, 02/24/2009 - 09:24
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If both paths have equal cost to the destination, then Eigrp will loadbalnce across equal paths (By default 4 paths).

If they have different Cost, then you will need the (Variance) command under the eigrp process.



allen.malanda_2 Wed, 02/25/2009 - 07:04
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They have different cost. How will I configure variance between the two devices?


Richard Burts Tue, 02/24/2009 - 09:29
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You do not tell us whether both devices are learning the same prefixes (same network/subnets with the same mask) and this is important in setting one as primary.

Assuming that both devices are learning the same prefixes I would suggest that you configure an offset list on the backup device to add an amount to the metric that it learns over the MPLS. By adding to the metric learned it will make those routes less favorable and the router on the Metro E will become the primary.



ajay.manam Wed, 02/25/2009 - 07:20
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hi allen,

why cant we run hsrp between these two L3 devices , so that one acts as primary , another acts as standby ,

am i wrong ?

thanks and regards

......ajay krishna...........

allen.malanda_2 Wed, 02/25/2009 - 07:37
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The two devices are a L3 switch and a router. We manage the L3 switch and router is managed by Verizon business. The metro e (10meg) is connected to the L3 switch. This is our primary route. The router is connected to the MPLS cloud, and it should operate as backup route. With our design hsrp is not a good option. We really want EIGRP to take care this routing automatically. If the metro circuit is running slow, we want the traffic to follow through the MPLS router.


parvillar Wed, 02/25/2009 - 10:52
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I think what the first task you have to do is see the eigrp topology table in your L3 device. If both routes to the destination are present then calculate FD (succesor)/FD (feasible succesor) and you obtain the minumun variance to configure.

In other way, if only have a route in the topology table to the destination (central officce) it means that the AD of the backup path no match the condition AD



ajay.manam Wed, 02/25/2009 - 21:05
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absolutely you are correect

regards ...............

ajay krishna

naveen_b81 Wed, 02/25/2009 - 23:51
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If you are running EIGRP on the L3 switch, router and the remote devices, your requirement should be already met as the Metro Ethernet (assuming FA) will be preferred over the MPLS (assuming Serial). If not, you can assign high bandwidth to the Metro Ethernet interface and low bandwidth to the link, thus making Metro Ethernet the primary route.

YOu requirement of switchover when the metro circuit running slow (assuming high bandwidth utilization), can be achieved in 2 ways

1. Adding the load on the link to the metric of eigrp (NOT RECOMMENDED).

2. Using Variance command so that the traffic by default load balances between metro and MPLS based on the available bandwidth on both of them.

allen.malanda_2 Thu, 02/26/2009 - 08:55
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That's exactly what I want to accomplish. What are the variance commands for EIGRP?



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