SMC Networks SMC6724L3 manual 232, Configuring Global PIM-DM Settings

CONFIGURING THE SWITCH

network. If it is not, the router drops the packet and sends a prune message back out the source interface. If it is the same interface used by the unicast protocol, then the router forwards a copy of the packet to all the other interfaces for which is has not already received a prune message for this specific source-group pair.

DVMRP holds the prune state for about two hours, while PIM-DM holds it for only about three minutes. This results in more flooding than encountered with DVMRP, but this the only major trade-off for the lower processing overhead and simplicity of configuration for PIM-DM.

Configuring Global PIM-DM Settings

PIM-DM is used to route multicast traffic to nodes which have requested a specific multicast service via IGMP. It uses the router’s unicast routing table to determine if the interface through which a packet is received provides the shortest path back to the source. This is done on a per hop basis back toward the source of the multicast delivery tree. PIM-DM uses three different techniques to dynamically reconfigure the multicast spanning tree: broadcasting, pruning, and grafting.

To use PIM-DM, you must enable it globally for the router as described below, and for each interface that will support multicast routing as described in the next section. Also note that IGMP must be enabled to allow the router to determine the location of group members.

Web – Click Routing Protocol, PIM-DM, General Settings. Enable or disable PIM-DM globally for the router, and click Apply.

3-232