ZyXEL Communications XS3800-28, User Manual, Page: 494 / 789

Chapter 66 IGMP
XS3800-28 User’s Guide
494
C
HAPTER
66
IGMP
This chapter shows you how to configure the Switch as a multicast router.
66.1 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 388 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.