Rendezvous-point tree (RPT)

When a DR in a VLAN receives traffic for a particular multicast group from a source on that VLAN, the DR encapsulates the traffic and forwards it to the RP elected to support that multicast group. The RP decapsulates the traffic and forwards it on toward the multicast receiver(s) requesting that group. This forms an RPT extending from the DR through any intermediate PIM-SM routers leading to the PIM-SM edge router(s) for the multicast receiver(s) requesting the traffic. (If the RP has no current join requests for the group, the traffic is dropped at the RP.)

Example PIM-SM domain with RPT active to support a host joining a multicast group