Multicast routing and switching is the functionality of a network that allows a single host (the multicast server) to send a packet to a group of hosts. With multicast, the server is not forced to duplicate and send enough packets for all the hosts in a group. Instead, multicast allows the network to duplicate packets for all of the hosts in a group. Multicast greatly reduces the bandwidth required to send data to a group of hosts. IP multicast routing is a function that allows multicast traffic to be forwarded from one subnet to another across a routing domain.
NoteYou should configure IP unicast routing before you configure IP multicast routing.