Igmp Snooping Configuration; Igmp Snooping Overview; Principle Of Igmp Snooping - 3Com 4500G Family Configuration Manual

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IGMP Snooping Configuration

When configuring IGMP Snooping, go to the following sections for information you are interested in:

IGMP Snooping Overview

IGMP Snooping Configuration Task List
Displaying and Maintaining IGMP Snooping
IGMP Snooping Configuration Examples
Troubleshooting IGMP Snooping Configuration
IGMP Snooping Overview
Internet Group Management Protocol Snooping (IGMP Snooping) is a multicast constraining
mechanism that runs on Layer 2 devices to manage and control multicast groups.

Principle of IGMP Snooping

By analyzing received IGMP messages, a Layer 2 device running IGMP Snooping establishes
mappings between ports and multicast MAC addresses and forwards multicast data based on these
mappings.
As shown in Figure
broadcast to all devices at Layer 2. When IGMP Snooping is running on the switch, multicast packets for
known multicast groups are multicast to the receivers, rather than broadcast to all hosts, at Layer 2.
Figure 1-1 Before and after IGMP Snooping is enabled on the Layer 2 device
Multicast packet transmission
without IGMP Snooping
Source
Host A
Receiver
Multicast packets
IGMP Snooping forwards multicast data to only the receivers requiring it at Layer 2. It brings the
following advantages:
1-1, when IGMP Snooping is not running on the switch, multicast packets are
Multicast router
Layer 2 switch
Host C
Receiver
Host B
Multicast packet transmission
when IGMP Snooping runs
Multicast router
Source
Layer 2 switch
Host A
Receiver
Host B
1-1
Host C
Receiver