Brocade Multi-Service IronWare Multicast Configuration Gui Instrukcja Użytkownika Pobierz pdf (Strona 104)

92 Multi-Service IronWare Multicast Configuration Guide

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DVMRP overview

In Figure 13, the root node (R1) is forwarding multicast packets for group 229.225.0.2 that it

receives from the server to its downstream nodes, R2, R3, and R4. Router R4 is an intermediate

router with R5 and R6 as its downstream routers. Because R5 and R6 have no downstream

interfaces, they are leaf nodes.

The receivers in this example are those workstations that are resident on routers R2, R3, and R6.

Pruning a multicast tree

After the multicast tree is constructed, pruning of the tree will occur after IP multicast packets

begin to traverse the tree.

As multicast packets reach leaf networks (subnets with no downstream interfaces), the local IGMP

database checks for the recently arrived IP multicast packet address. If the local database does

not contain the address (the address has not been learned), the router prunes (removes) the

address from the multicast tree and no longer receives multicasts until the prune age expires.

In Figure 14, Router 5 is a leaf node with no group members in its local database. Consequently,

Router 5 sends a prune message to its upstream router. This router will not receive any further

multicast traffic until the prune age interval expires.

FIGURE 13 Downstream broadcast of IP multicast packets from source host

FIGURE 14 Pruning leaf nodes from a multicast tree

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Brocade Multi-Service IronWare Multicast Configuration Gui Instrukcja Użytkownika Strona 104