Brocade Multi-Service IronWare Multicast Configuration Guide (Supporting R05.6.00) - Manual (Page 33)

Multi-Service IronWare Multicast Configuration Guide 21
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IP multicast boundaries
1
Figure 3 shows a topology in which R1 through R11 have IP addresses in ascending order i.e. R1
having the lowest ip address and R11 having the highest. All the routers are PIM enabled routers.
The links emanating from each router are ECMP links. The existing behavior path utilization is
indicated in red. With the highest IP address neighbor chosen for the ECMP paths available, the
multicast cache entries get to utilize only the R1-R4-R11-SRC/RP path.
FIGURE 3 Path utilization without Multicast ECMP support
With the ECMP support turned on, the multicast entries will be distributed among the equal cost
next hops as indicated in green for better utilization of the available paths.
FIGURE 4 Path utilization with Multicast ECMP support
The load distribution is achieved by distributing the multicast cache entries (*,G or S,G) to the
available paths thus distributing the traffic. Two different methods are widely used to achieve this
distribution.
1. Hash based - Load splitting
2. Least used path based - Load balancing
Brocade devices support the Hash based method of load distribution for multicast ECMP.