Eigrp Variance

Unanswered Question
Oct 20th, 2008

Hi Guys,

Just running through some EIGRP and while doing variance my attaention was pointed to this

R5#sh ip ro

Routing entry for

Known via "eigrp 100", distance 90, metric 10639872, type internal

Redistributing via eigrp 100

Last update from on Serial0/2/0, 00:03:38 ago

Routing Descriptor Blocks:, from, 00:03:38 ago, via Serial0/2/0

Route metric is 40640000, traffic share count is 21

Total delay is 25000 microseconds, minimum bandwidth is 64 Kbit

Reliability 255/255, minimum MTU 1500 bytes

Loading 1/255, Hops 1

*, from, 00:03:38 ago, via Serial0/1/0

Route metric is 10639872, traffic share count is 80

Total delay is 25000 microseconds, minimum bandwidth is 256 Kbit

Reliability 255/255, minimum MTU 1500 bytes

Loading 1/255, Hops 1

What does the 'traffic share count is' denote???

So i have sucessfully implemented the variance command. But what doe sthis output mean?



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Overall Rating: 4 (1 ratings)
Istvan_Rabai Tue, 10/21/2008 - 02:28

Hi Stephen,

On serial 0/2/0 your traffic share count is 21.

On serial 0/1/0 your traffic share count is 80.

Their ratio expresses the ratio of unequal load-balancing.

Unequal load balancing takes into account the metrics of each route and distributes traffic between the routes in inverse proportion.

Routes with higher metric will serve less traffic, routes with lower metric will serve more traffic, according to their ratio of metrics.

Look at the ratio of metrics:

10639872/40640000 will give you a very similar result as 21/80.



stephen.stack Tue, 10/21/2008 - 02:52

Excellent... this is what is suspected. So am i to assume that if i adjust the bandwidth command, the metric will adjust and then a calculation is carried out which in turn adjusts these figure?

This is good information to know in the real world!



lffrwatson Tue, 10/28/2008 - 06:06

Variance tricks EIGRP to do unequal load balancing. It can also do equal load balancing with no problems. By tweaking the bandwidth command on the interface it will adjust the algorithm. The metric is bandwidth and delay and assuming the same cable type is used the delay should be pretty equal.


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