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The oilist for a router interface can be null or in the (*,G)
or (S,G) state. An interface can also be in both the (S,G) and (*,G)
states. In Figure 6-10, router A has PIM-DM enabled on all
interfaces. When the host attaches to the E1 interface of router A,
it will join the multicast group 224.0.18.10 by sending an IGMP join
message to router A. Router A will add the entry (*,224.0.18.10) to
the E1 interface, indicating that multicast traffic for group
224.0.18.10 from any source should be sent onto the ethernet
interface. The same (*,G) state can exist in more than one oilist.
Input interfaces for a multicast group will have (S,G) state and the
same (S,G) state will not exist on more than one interface since a
router can only have one best path back to a multicast source. The
input interface is the interface over which a router expects to
receive multicast traffic from a specific source. This interface is
simply the RPF interface. |
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