Multicast Routing Overview

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.

IP multicast routing requires the following functions:
  • A router that can forward IP multicast packets
  • A router-to-router multicast routing protocol (for example, Protocol Independent Multicast (PIM)) to discover multicast routes
  • A method for the IP host to communicate its multicast group membership to a router (for example, IGMP (Internet Group Management Protocol))


You should configure IP unicast routing before you configure IP multicast routing.