In the multicast models, an IP packet's destination address is a multicast group address. A multicast source sends data packets to the host group identified by the destination address. To transmit packets to all receivers, a router on the forwarding path needs to send a packet received from an incoming interface to many outgoing interfaces. To perform these tasks, multicast models use the following functions:
A multicast routing table guides the forwarding of multicast packets.
Reverse path forwarding (RPF) ensures that multicast routing uses the shortest path tree. RPF is used by most multicast protocols to create multicast route entries and forward packets.