Qtech QSW-2900-24T-AC [92/209] Igmp snooping overview

Qtech QSW-2900-24T-AC [92/209] Igmp snooping overview
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5.4 IGMP Snooping Configuration
5.4.1 IGMP Snooping Overview
Internet Group Management Protocol Snooping (IGMP Snooping) is a multicast constraining mechanism that
runs on Layer 2 devices to manage and control multicast groups.
By listening to and analyzing IGMP messages, a Layer 2 device running IGMP Snooping establishes
mappings between ports and multicast MAC addresses and forwards multicast data based on these mappings.
As shown in Figure 1, when IGMP Snooping is not running on the switch, multicast packets are broadcast to
all devices at Layer 2. When IGMP Snooping is running on the switch, multicast packets for known multicast groups
are multicast to the receivers, rather than broadcast to all hosts, at Layer 2.
Figure 1 Before and after IGMP Snooping is enabled on the Layer 2 device
5.4.2 Basic Concepts in IGMP Snooping
a) IGMP Snooping related ports
As shown in Figure 2, Router A connects to the multicast source, IGMP Snooping runs on Switch A and
Switch B, Host A and Host C are receiver hosts (namely, multicast group members).

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