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GS-4012F/4024 User’s Guide
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CHAPTER 29
IGMP
This chapter shows you how to configure the Switch as a multicast router.
29.1 IGMP Overview
IP multicast is an IETF standard for distributing data to multiple recipients. The following
figure shows a multicast session and the relationship between a multicast server, multicast
routers and multicast hosts. A multicast server transmits multicast packets and multicast
routers forward multicast packets to multicast hosts.
Figure 126 IP Multicast
A host can decide to join or leave a multicast group at any time. A host can also be a member
of more than one multicast group. Multicast groups are identified by IP addresses in the Class
D range (224.0.0.0 to 239.255.255.255). A multicast server sends packets addressed to a
particular multicast group (multicast IP address).
IGMP (Internet Group Management Protocol) is used by multicast hosts to indicate their
multicast group membership to multicast routers. Multicast routers can also use IGMP to
periodically check if multicast hosts still want to receive transmission from a multicast server.
In other words, multicast routers check if any hosts on their network are still members of a
specific multicast group.
Server
Multicast Routers
Hosts