3Com Switch 8800 Advanced Software V5 Configuration Guide

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IGMP SNOOPING CONFIGURATION
When configuration IGMP Snooping, go to the following sections for information
you are interested in:
■ “IGMP Snooping Overview” on page 539
■ “Configuring Basic Functions of IGMP Snooping” on page 544
■ “Configuring IGMP Snooping Port Functions” on page 546
■ “Configuring IGMP-Related Functions” on page 549
■ “Configuring a Multicast Group Policy” on page 552
■ “Displaying and Maintaining IGMP Snooping” on page 555
■ “IGMP Snooping Configuration Examples” on page 555
■ “Troubleshooting IGMP Snooping Configuration” on page 560
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For details about IGMP and PIM, refer to “IGMP Configuration” on page 523 and
“PIM Configuration” on page 563.
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 switch (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 169, when IGMP Snooping is not running on the switch,
multicast packets are 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.