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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.
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