CGMP Join

CGMP Join
Hosts do not use CGMP; only the switches and routers that the host connects to use it. When
a host sends an IGMP report (Membership Report) advertising membership of a multicast
group, the message is forwarded to the router (that is, an actual multicast router, an RSM, or
an MSFC) for processing. The router sees the request and processes it accordingly. The multicast
group is set up, and the two MAC addresses are generated. The router then gives the switch
the CGMP message. With the CGMP message, the switch can assign the multicast group to the
port of the requesting host. You can see the entire process in Figure 19.11.