SMC Networks SMC6724L3 manual 224, Command Usage

CONFIGURING THE SWITCH

Command Usage

Broadcasting periodically floods the network with traffic from any active multicast server. If IGMP snooping is disabled, multicast traffic is flooded to all ports on the router. However, if IGMP snooping is enabled, then the first packet for any source group pair is flooded to all DVMRP downstream neighbors. If a packet is received through an interface that the router determines to be the shortest path back to the source (based on interface metrics), then the router forwards the packet on all interfaces except for the incoming interface.

The router will transmit a prune message back out the receiving interface (i.e., the parent interface) to its upstream neighboring router if there are no group members on its child interfaces. A prune message tells the upstream router to stop forwarding packets for a particular source-group pair for the prune lifetime.

If the router that previously sent a prune message now discovers a new group member on one of its connections, it sends a graft message to the upstream router. When an upstream router receives this message, it cancels the prune message. If necessary, graft messages are propagated back toward the source until reaching the nearest live branch in the multicast tree.

source

flooding

potential hosts

source

pruning

source

grafting

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