Understanding Where Multicast Packets are Forwarded

Figure 3-1 : A Network With Multicast Routers

• If people on networks A, C, and D are listening for packets, as shown in the figure, all four networks receive the multicast packets.

• If people on networks A and C are listening for packets, networks A, B, and C receive the multicast packets.

• If three or more people on network A are listening for packets, networks A and B receive the multicast packets. The multicast routing protocol prevents packets from being sent to "leafs" of the network, such as networks C and D; however, it doesn't prevent packets from being sent to interior networks, such as network B.