IP Multicast Routing
In Chapter 16, “Introduction to IP Multicasting,” you learned how a multicast router communicates
with hosts and then decides whether to forward or stop the multicast traffic on a subnet. But how
does a multicast router receive the group traffic? How is the multicast traffic forwarded from a
source so that all the group users receive it? This chapter provides answers to those questions.
This chapter first defines the multicast routing problem by identifying the difference between
unicast and multicast routing. It then provides an overview of the basic design concepts of
multicast routing protocols, and shows how they solve multicast routing problems. Next, the
chapter covers the operations of the Protocol Independent Multicast routing protocol in dense
mode (PIM-DM) and sparse mode (PIM-SM). The chapter also covers the basic functions of
Distance Vector Multicast Routing Protocol (DVMRP) and Multicast OSPF (MOSPF).
■ IGMPv2
■ Group Addresses
■ Shared Trees
■ Source Trees
■ Protocol Independent Multicast (PIM)
Mechanics
■ PIM Sparse Mode
■ Auto-RP
■ Anycast RP