In my previous post, I made an analogy comparing PIM-DM to PIM-SM. In this Part, I will describe in technical detail how exactly PIM-DM and PIM-SM work. Before talking about PIM-DM and PIM-SM it’s important to do a quick review of the Internet Group Management Protocol (IGMP), routing protocol considerations and Neighbor Discovery process.
IGMP is used to establish multicast group memberships from hosts to routers. A host will send an IGMP join message (IGMP membership report) in order to join a multicast group. It is important to remember that PIM is a communication protocol used between routers and IGMP is used from hosts to routers. Continue reading