HP 6125G HP 6125G & 6125G/XG Blade Switches IP Multicast Configuration - Page 23
Configuring IGMP snooping, Overview, Basic concepts in IGMP snooping, IGMP snooping related ports
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Configuring IGMP snooping Overview Internet Group Management Protocol (IGMP) snooping is a multicast constraining mechanism that runs on Layer 2 devices to manage and control multicast groups. By analyzing received IGMP messages, a Layer 2 device that runs IGMP snooping establishes mappings between ports and multicast MAC addresses, and forwards multicast data based on these mappings. As shown in Figure 10, without IGMP snooping enabled, the Layer 2 switch floods multicast packets to all devices at Layer 2. With IGMP snooping enabled, the Layer 2 switch forwards multicast packets for known multicast groups to only the receivers that require the multicast data at Layer 2. This feature improves bandwidth efficiency, enhances multicast security, and helps per-host accounting for multicast users. Figure 10 Before and after IGMP snooping is enabled on the Layer 2 device Basic concepts in IGMP snooping IGMP snooping related ports As shown in Figure 11, Router A connects to the multicast source, IGMP snooping runs on Switch A and Switch B, and Host A and Host C are receiver hosts as members of a multicast group. 12
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