Fundamentals of IGMP snooping
As shown in Figure 11, when IGMP snooping is not enabled, the Layer 2 switch floods multicast packets to all hosts in a VLAN or VSI. 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
