Calculate EIGRP Variance from Metrics of Installed Routes

It is possible to determine the minimum variance value used in an EIGRP load-balancing scenario from the feasible distance of all installed EIGRP routes to a particular destination.

Specifically, variance is greater than or equal to the metric of the feasible successor divided by the metric of the successor, rounded up.

Note, that the result is not necessarily the actual variance configured, but it is an indicator of the lowest possible variance that may have been configured on the device.

For example, take a look at the following routing table entries for EIGRP where variance has been configured:

R1#show ip route | begin 5.5.5.5
D 5.5.5.5 [90/412160] via 192.168.13.3, 00:00:42, Ethernet1/0
          [90/158720] via 192.168.12.2, 00:00:42, FastEthernet0/0

To determine the lowest possible variance that can result in this ECMP, we use the following formula:

412160 / 158720 = 2.59  rounded up --> 3

So the lowest possible variance value that can result in this ECMP is 3. The actual configured variance value may be higher, but it is definitely not lower.

https://networklessons.com/eigrp/eigrp-variance-command-example

https://networklessons.com/eigrp/eigrp-unequal-cost-load-balancing