Trainsignal, Chapter 2 Lecture 3 - Autosummarisation

Trainsignal, Chapter 2 Lecture 2 - The variance command

Okay, We have the network topology below:

The EIGRP routing table on R1 is below, we can see we have 2 sucessors for the ethernet segment (172.23.23.0) and the loopbacks of R2 (2.2.2.2) and R3 (3.3.3.3) we have only 1 successor 

But we do have a backup route to these two loopbacks (a Feasible Successor)

Why are they a  Feasible Successor ? because the metric is different, yet for the 172.23.23.0 network the metrics are the same so we can equal-cost load balance across the links.

SO lets look at the lab more closely:

NOTE: 
* By default the variance command is set to 1 (as 0 would be disabling equal-cost load balancing -which you cannot do as the range is from 1 - 128)

* Changing the variance command does not bring down the neighbourship, HOWEVER you will need to clear the route for that network as EIGRP only sends UPDATES when there is a TOPOLOGY CHANGE

* The variance command is global and is a ALL or NOTHING!