3Com 2500 manual Multicast, Interfaces, Which are described in this section

Multicast Interfaces 5-5

Pruning Pruning is a method used in the RPF algorithm to forward packets to a spanning tree only if group members exist in the tree. This method results in fewer spanning trees, but it requires dynamic updates to the routing table.

Nodes that are at the border of the network and have no point beyond them in the RPF spanning tree are called leaf nodes. Leaf nodes all receive the first multicast packet. If a group member is attached to the leaf node, the node continues to accept packets. If no group member is attached to the leaf node, the node sends back a “prune message” to the router that sent the packet. The message tells the router to send no further packets to this group. In the LANplex system, the Administration Console IP multicast CacheDisplay includes information about when pruning will occur on the spanning tree.

Multicast	Multicast interfaces on the LANplex system have several characteristics
Interfaces	which are described in this section:

DVMRP Metric Value The DVMRP metric value determines the cost of a multicast interface. The higher the cost, the slower the link. The default value is 1.

Time-To-Live (TTL) This TTL threshold determines whether the interface will forward multicast Threshold packets to other switches and routers in the subnet. If the interface TTL is

greater than the packet TTL, then the interface does not forward the packet. The default value is one 1, which means that the interface forwards most packets.