04-10-2008 12:06 AM - edited 03-05-2019 10:18 PM
How does variance help in EIGRP load balancing ? How do we decide on the variance value & where do we configure this ? why would we require "trafic share min" since it's equivalent to having no variance configured ?
04-10-2008 12:17 AM
Variance is used when you have more than one route to a destination but they are not equal cost eg.
Link 1 = 128Kbps
Link 2 - 256Kbps
Under default settings EIGRP would only use Link 2. if you configure a variance eg.
router eigrp 1
variance 2
then EIGRP will now use both links and for every 2 packets sent on Link 2 it will send one on link 1.
The traffic-share min command if applied to the above example would ensure that EIGRP only used Link 2.
Jon
04-10-2008 12:28 AM
Thanks for your quick reply Jon!
So, this would help in load balancing right ?
How would work on a scenario with 3 paths between router A and B with metric / bandwidth of 1.4Mb, 2.48Mb & 4.09Mb? How do we implement Variance here ?
04-10-2008 12:45 AM
You would need a variance value of 3 to allow EIGRP to use all 3 links in it's forwarding.
Jon
04-10-2008 01:00 AM
what does the variance value depend on? On the number of links that participate in the load sharing / balancing?
04-10-2008 01:05 AM
No its worked out from the bandwidths, so from your example
1.4Mb, 2.48Mb & 4.09Mb
With a variance of 2 EIGRP would only use the 2.48Mb and 4.09Mb links - why
2.48 x 2 = 4.96 which is greater than 4.09
1.4 x 2 = 2.8 which is less then 4.09
so the 1.4Mb link would not be used but
3 x 1.4 = 4.2 which is greater than 4.09.
Jon
04-10-2008 01:24 AM
Thanks a lot Jon. I gotthe concept.
Discover and save your favorite ideas. Come back to expert answers, step-by-step guides, recent topics, and more.
New here? Get started with these tips. How to use Community New member guide