Multicast load splitting across equal-cost paths

When you have multiple equal cost routing paths in a topology where you have multicast traffic, by default, all multicast routing techniques will choose the PIM neighbor with the highest IP address.

You can, however, configure multicast so that it dynamically takes advantage of multiple equal-cost paths using what is known as IP Multicast Load Splitting across Equal-Cost paths.

There are two methods to employ this:

  1. Enable ECMP multicast load splitting based on source address, source and group address, or based on source, group, and next-hop address. After the equal-cost paths are recognized, ECMP multicast load splitting operates on a per (S, G) basis, rather than a per-packet basis as in unicast traffic.
  2. Consolidate two or more equal-cost paths into a GRE tunnel and allow unicast routing to perform the load balancing.

When employing features such as HSRP, it is recommended that HSRP-Aware PIM be used to take advantage of the load balancing and redundant capabilities delivered by HSRP.