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Configuring igmp snooping, Overview, Basic igmp snooping concepts – H3C Technologies H3C S12500-X Series Switches User Manual

Page 24: Igmp snooping related ports, Multicast support for vpns, Introduction to vpn instances

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Configuring IGMP snooping

Overview

IGMP snooping runs on a Layer 2 switch as a multicast constraining mechanism to improve multicast

forwarding efficiency. It creates Layer 2 multicast forwarding entries from IGMP packets that are
exchanged between the hosts and the router.

As shown in

Figure 11

, when IGMP snooping is not enabled, the Layer 2 switch floods multicast packets

to all hosts. When IGMP snooping is enabled, the Layer 2 switch forwards multicast packets of known

multicast groups to only the receivers.

Figure 11 Multicast packet transmission without and with IGMP snooping

Basic IGMP snooping concepts

IGMP snooping related ports

As shown in

Figure 12

, IGMP snooping runs on Switch A and Switch B, and Host A and Host C are

receivers in a multicast group.