Web-based Configuration Guide L2 Multicast
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Table 5-1 Description of Configuration Parameters of Global Multicast
The Internet Group Management Protocol (IGMP) is a TCP/IP
protocol that manages members in an IPv4 multicast group
and runs on the multicast devices and hosts residing on the
stub of the multicast network, creating and maintaining
membership of the multicast group between the hosts and
connected multicast devices. There are three versions of
IGMP: IGMPv1, IGMPv2, IGMPv3.
This parameter is used to set the highest version of IGMP
packets that can be processed by Layer 2 multicast, and can
be set to IGMPv2 or IGMPv3.
After this function is enabled, to reduce the number of packets
in the network, save network bandwidth and ensure the
performance of the IGMP multicast device, the switch forwards
only one report packet to the multicast router if multiple
downlink clients connected to the switch simultaneously send
the report packet to demand the same multicast group.
When both the global and VLAN multicast functions are
enabled, the processing method for receiving unknown
multicast packets can be set to Discard or Flood.
5.3 IGMP Snooping
5.3.1 Overview
The Internet Group Management Protocol (IGMP) snooping is an IP multicast snooping mechanism running on
a VLAN to manage and control the forwarding of IP multicast traffic within the VLAN. It implements the L2
multicast function.
Generally, multicast packets need to pass through L2 switches, especially in some local area networks (LANs).
When the Layer 2 switching device does not run IGMP Snooping, the IP multicast packets are broadcast in the
VLAN; when the Layer 2 switching device runs IGMP Snooping, the Layer 2 device can snoop the IGMP protocol
packets of the user host and the upstream PIM multicast device. In this way, an Layer 2 multicast entry is
established, and IP multicast packets are controlled to be sent only to group member receivers, preventing
multicast data from being broadcast on the Layer 2 network.
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