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24 Description of IGMP Snooping and MLD Snooping
multicast is used on a network to which a Layer 2 switch is connected, unnecessary
multicast traffic might be sent to ports that have no multicast traffic recipients.
IGMP snooping and MLD snooping monitor IGMP or MLD messages and forward multicast
traffic to ports to which recipients are connected. This functionality can be used to suppress
the forwarding of unnecessary multicast traffic for more efficient use of networks. The
following figure gives an overview of IGMP snooping and MLD snooping.
Figure 24-2 Overview of IGMP snooping and MLD snooping
To detect ports to which multicast traffic recipients are connected, the Switch monitors
group management protocol packets. The group management protocol sends and receives
group membership information between router hosts by using IGMP on IPv4 networks and
MLD on IPv6 networks. The protocol detects packets sent from the host, indicating group
participation and detachment, to learn the connected ports to which multicast traffic should
be forwarded.
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