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Configuring IGMP snooping
Overview
IGMP snooping runs on a Layer 2 device 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 10,
when IGMP snooping is not enabled, the Layer 2 device floods multicast
packets to all hosts. When IGMP snooping is enabled, the Layer 2 device forwards multicast packets
of known multicast groups to only the receivers.
Figure 10 Multicast packet transmission without and with IGMP snooping
Basic IGMP snooping concepts
IGMP snooping related ports
As shown in Figure 11, 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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