PIM-DM configuration example

When the routing switch detects a new multicast flow, it initially floods the traffic throughout the PIM-DM domain, then it prunes the traffic on the branches (network paths) where joins have not been received from individual hosts. The following is a sample topology diagram for a PIM-DM configuration.

Figure 1  PM-DM Configuration Examples

The routing switch maintains individual branches in the multicast tree as long as there is at least one host maintaining a membership in the multicast group. When all the hosts in a particular subnet drop out of the group, PIM-DM prunes that interface from the multicast tree. Similarly, if the routing switch detects a join from a host in a pruned interface, it adds that branch back into the tree.

Unlike PIM-SM, the number of mroutes created with dense mode is typically high since the source router floods the traffic initially to all the PIM neighbors. If we have two routers connected with many VLAN trunks, the resulting mroutes on the receiver router will be proportional to the number of SVIs configured. Ensure that the given flows are within the limits of the receiver router's mroute scale.