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Load balancing in EIGRP network


we have to reach a site in UK through India

this is the network topplogy in short

A-----connected through 512 kbps delay 24000 -------B


Router "A" is connected to Router "C" through a 512 kbps, delay 24000 link and Router "B" is connected to Router "C" through a 2 Mbps, delay 30000 link.

The delay has been manually configured on the serial ports.

By using the rule

[(1000000/min bandwidth) + delay]*256, we have calculated that "variance 2" command on the Router A will load balance, are we right and moreover does anyone have any method other than the command like increasing the B/W or so to achieve load balance.


Community Member

Re: Load balancing in EIGRP network

Well, you can achieve load balancing by changing the default values of delay, Bandwidth.

But it is bit tricky.

Both the routers Router C and Router B should aadvertise equal metrics (AD-adverised Distance)to Router A.

Moreover Router A should learn FD(feasible distance) via both the links equal.

This will only give loadbalance from traffic going from ROUTER A to ROUTER C.

Where as again problem araises for traffic coming from ROUTER C to ROUTER A.

Otherway round what you can do is,

If router A, C both supports Policy based routing,

Cofigure some hosts to use link A-B, and other A-C

and vice-versa from Router C

Community Member

Re: Load balancing in EIGRP network


Thank you for your response,

does my calculation for the "variance 2" command make any sense????



Re: Load balancing in EIGRP network

You can tell what the variance should be by looking in the EIGRP topology table--both routes should be there. If you look at the metric associated with each possible path, you can simply divide the lowest metric into the highest metric, and round up to the nearest whole number.

If you are going to calculate the metrics yourself, you have to remember the order in which the calculations occur, and rememebr that EIGRP doesn't use floating point when calculating metrics, to get the metric calculation right. If you calculate the metrics for each link, and find that the lower cost link is exaclty half the cost of the higher cost link, you will still have to use a variance of 3, since the lower cost link has to be _less than_ the variance multiplied by the higher cost link to be used for unequal cost load sharing.

7680005 & 11143936 seem to be the two metrics involved here, and you'd need to set the variance to 3, I think.


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