3com 5500-ei pwr Instruccion De Instalación
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IGMP Snooping Configuration
When configuring IGMP snooping, go to these sections for information you are interested in:
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In this manual, the term “router” refers to a router in the generic sense or a Layer 3 Ethernet switch
running an IP multicast protocol.
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.
Principle of IGMP Snooping
By analyzing received 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
, 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.
However, multicast packets for unknown multicast groups are still broadcast at Layer 2.