Patent ID: 7860093

Claim:
A method comprising: receiving at a network device designated as a secondary designated router or forwarder in a Protocol Independent Multicast (PIM) distribution tree, an indication that a receiver wants to join a multicast group; transmitting a PIM join message upstream towards a source or a rendezvous point in said distribution tree, in response to said received indication; receiving multicast data from a source at the network device; dropping the multicast data if a primary designated router or forwarder is operating to forward the multicast data from the source to the receiver; and adding the receiver to an outgoing interface list at the network device and forwarding the multicast data to the receiver only if a failure occurs at said primary designated router or forwarder; wherein said receiving an indication that a receiver wants to join a multicast group, said transmitting the PIM join message, and said receiving multicast data are performed when both said primary and secondary designated routers or forwarders are operating during normal operation at said primary designated router or forwarder.