H3C Technologies H3C WX3000E Series Wireless Switches - Manual (Page 168)

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IGMP snooping configuration
Overview
Internet Group Management Protocol (IGMP) snooping is a multicast constraining mechanism that runs
on Layer 2 devices to manage and control multicast groups.
By analyzing received IGMP messages, a Layer 2 device that is running IGMP snooping establishes
mappings between ports and multicast MAC addresses and forwards multicast data based on these
mappings.
As shown in
Figure 131 , when IGMP snooping is not running on the switch, multicast packets are flooded
to all devices at Layer 2. However, 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 131 Multicast forwarding before and after IGMP snooping runs
IGMP snooping sends Layer 2 multicast packets to the intended receivers only. This mechanism provides
the following advantages:
• Reducing Layer 2 broadcast packets and saving network bandwidth
• Enhancing the security of multicast packets
• Facilitating the implementation of accounting for each host
For more information about IGMP snooping, see H3C WX Series Access Controllers IP Multicast
Configuration Guide.