ZyXEL Communications MES-2110 manual IP Multicast Addresses, Igmp Snooping, 123

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IGMP

17.1 Overview

Traditionally, IP frames 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 frames to just a group of hosts on the network.

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

17.1.1 IP Multicast Addresses

In IPv4, a multicast address allows a device to send frames to a specific group of hosts (multicast group) in a different subnetwork. 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).

17.1.2 IGMP Snooping

A MES-2110 can passively snoop on IGMP frames transferred between IP multicast routers/switches and IP multicast hosts to learn the IP multicast group membership. It checks IGMP frames passing through it, picks out the group registration information, and configures multicasting accordingly. IGMP snooping allows the MES-2110 to learn multicast groups without you having to manually configure them.

The MES-2110 forwards multicast traffic destined for multicast groups (that it has learned from IGMP snooping or that you have manually configured) to ports that are members of that group. IGMP snooping generates no additional network traffic, allowing you to significantly reduce multicast traffic passing through your MES-2110.

MES-2110 User’s Guide

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