3Com Switch 4800G 24-Port - Igmp Snooping; IGMP Snooping Overview

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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” on page 553
■ “IGMP Snooping Configuration Task List” on page 558
■ “Displaying and Maintaining IGMP Snooping” on page 569
■ “IGMP Snooping Configuration Examples” on page 570
■ “Troubleshooting IGMP Snooping Configuration” on page 577
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 IP addresses and forwards
multicast data based on these mappings.
As shown in Figure 170, 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.