IP multicast uses the Protocol Independent Multicast (PIM) routing protocol between routers to
determine the path on the distribution tree that multicast packets take from the source
to the receivers (multicast group members). A Palo Alto Networks® firewall supports PIM
Sparse Mode (PIM-SM) (
RFC 4601), PIM Any-Source Multicast (ASM)
(sometimes referred to as PIM Sparse Mode), and PIM Source-Specific Multicast (SSM). In
PIM-SM, the source does not forward multicast traffic until a receiver (user) belonging
to a multicast group requests that the source send the traffic. When a host wants to
receive multicast traffic, its implementation of IGMP sends an IGMP Membership report
message, and the receiving router then sends a PIM Join message to the multicast group
address of the group it wants to join.