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When the oilist for a particular interface becomes null,
there are no downstream PIM-DM routers or multicast receivers
attached to the network. The interface does not need to transmit
multicast traffic and can, therefore, be pruned from the
source-based delivery tree. In Figure 6-13, router A initially
receives multicast traffic from the source and floods the traffic
onto all interfaces in the oilist. Router B is a PIM-DM-enabled
router, but has no attached downstream PIM-DM routers or mulitcast
receivers. Router B will send a prune message to its upstream router
for this particular multicast source. When router A receives the
prune from router B, router A’s oilist for the serial link will
become null, halting the forwarding of multicast traffic to router
B. |
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