EIGRP Refining the behavior of load balancing with traffic-share

By using the variance command, EIGRP is able to perform unequal cost load balancing To further refine how this load balancing takes place, you can use the traffic-share EIGRP command with the following options:

  • traffic-share balanced - This is the default behavior. Traffic to a particular destination is distributed proportionally to all entries in the routing table based on their metrics.
  • traffic-share min - Traffic is sent only across the minimum-cost path, even if there are multiple paths in the routing table. If two or more paths have an equal minimum-cost, load balancing will only take place across those paths.
  • traffic-share min across-interfaces - This is the same as traffic-share min with the exception that if there are two or more paths of equal minimum-cost, then load balancing will only occur across them if they have different exit interfaces. This results in better load balancing.

Note that traffic-share min and traffic-share min across-interfaces seem to cancel out the benefit of the variance command, since the load-balancing behavior is the same as when the variance command is not used. However, the benefit of using traffic-share min with the variance command is that even though traffic is sent over the minimum-cost path only, all feasible routes get installed into the routing table, which decreases convergence times in the event of a failure or topology change.