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Here is what my router is reporting. I set the variance to 100 just to see what is going on. This is using classic configuration and the RD for the two alternate links is 537600. If I multiply the FS (537600 with 2 -variance 2- that should be more than enough for the other two paths to satify the FC and to take part in unequal load balancing) As you can see in the outputs is not happening Why?

R4#sh ip eigrp topology all-links | se 10.20.12.0
P 10.20.12.0/24, 1 successors, FD is 537600, serno 50
        via 10.20.14.1 (537600/25600), Serial2/2
        via 10.20.46.6 (1049600/537600), Serial2/3
        via 10.20.34.3 (1049600/537600), Serial2/1

R4#sh ip route 10.20.12.0
Routing entry for 10.20.12.0/24
  Known via "eigrp 100", distance 90, metric 537600, type internal
  Redistributing via eigrp 100
  Last update from 10.20.14.1 on Serial2/2, 00:04:07 ago
  Routing Descriptor Blocks:
  * 10.20.14.1, from 10.20.14.1, 00:04:07 ago, via Serial2/2
      Route metric is 537600, traffic share count is 1
      Total delay is 21000 microseconds, minimum bandwidth is 1544 Kbit
      Reliability 255/255, minimum MTU 1500 bytes
      Loading 1/255, Hops 1
R4#sh run | s eigrp
router eigrp 100
 metric weights 0 0 0 1 0 0
 variance 120
 network 10.0.0.0
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The variance command doesn't change the feasibility condition; it changes the minimum metric allowed. Any paths must still meet the feasibility condition before they are considered for balancing with the variance command. Your reported distance through Serial2/2 is 25600, and only one of your paths meets the feasibility condition. The metrics for paths through Serial2/3 and Serial2/1 are greater than the FD, so they are not feasible successors.

In other words, a path must have a feasible successor in order for EIGRP to consider sending traffic over that path. See the portion I have highlighted in the document below.

How Does Unequal Cost Path Load Balancing (Variance) Work in IGRP and EIGRP?

Network Diagram

enter image description here

Variance

This section provides an example. In the network diagram, there are three ways to get to Network X:

  • E-B-A with a metric of 30
  • E-C-A with a metric of 20
  • E-D-A with a metric of 45

Router E chooses the path E-C-A with a metric of 20 because 20 is better than 30 and 45. In order to instruct EIGRP to select the path E-B-A as well, configure variance with a multiplier of 2:

router eigrp 1
network x.x.x.x
variance 2

This configuration increases the minimum metric to 40 (2 * 20 = 40). EIGRP includes all routes that have a metric of less than or equal to 40 and satisfy the feasibility condition. In the configuration in this section, EIGRP now uses two paths to get to Network X, E-C-A and E-B-A, because both paths have a metric of under 40. EIGRP does not use path E-D-A because that path has a metric of 45, which is not less than the value of the minimum metric of 40, because of the variance configuration. Also, the reported distance of neighbor D is 25, which is greater than the feasible distance (FD) of 20 through C. This means that, even if variance is set to 3, the E-D-A path is not selected for load balancing because Router D is not a feasible successor.

Note: For more information on variance, refer to Troubleshooting EIGRP Variance Command.

| improve this answer | |
  • Thanks a lot! I got it wrong, my impression was that it would also change the FC. Bottom line is that I have to change the metric directly if I want more paths in my case. – MiniMe Jul 1 '16 at 20:35

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