14

IGMP

14.1 Overview

Traditionally, IP packets are transmitted in one of either two ways - Unicast (1 sender to 1 recipient) or Broadcast (1 sender to everybody on the network). Multicast delivers IP packets to just a group of hosts on the network.

IGMP (Internet Group Multicast Protocol) is a network-layer protocol used to establish membership in a multicast group - it is not used to carry user data. See RFC 1112, RFC 2236, and RFC 3376 for information on IGMP versions 1, 2, and 3 respectively.

14.1.1What You Can Do in this Chapter

•Use the IGMP General screen to configure general IGMP proxy and IGMP packet processing settings (Section 14.2 on page 202).

•Use the IGMP Filter screens to control IGMP access (Section 14.3 on page 204).

•Use the IGMP ACL screens to block or allow access to specific multicast media channels (Section 14.4 on page 209).

14.1.2What You Need to Know

IP Multicast Addresses

In IPv4, a multicast address allows a device to send packets to a specific group of hosts (multicast group) in a different sub-network. A multicast IP address represents a traffic receiving group, not individual receiving devices. IP addresses in the Class D range (224.0.0.0 to 239.255.255.255) are used for IP multicasting. Certain IP multicast numbers are reserved by IANA for special purposes (see the IANA web site for more information).

IGMP Snooping

A layer-2 switch can passively snoop on IGMP Query, Report and Leave (IGMP version 2) packets transferred between IP multicast routers/switches and IP

 

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VSG1432-B101 Series User’s Guide