H3C Technologies H3C WX3000E Series Wireless Switches - Manual (Page 236)

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IGMP snooping configuration
IGMP snooping 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, an IGMP snooping–enabled Layer 2 device establishes
mappings between ports and multicast MAC addresses and forwards multicast data based on these
mappings.
As shown in
Figure 198 , when IGMP snooping is not running on the switch, multicast packets are flooded
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 198 Multicast forwarding before and after IGMP snooping runs
IGMP snooping forwards multicast data to only the receivers that require the data at Layer 2. It has 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
NOTE:
For more information about IGMP snooping, see H3C WX3000E Series Wireless Switches Switching
Engine Configuration Guide.