Draytek VigorSwitch G2080, User Manual, Page: 61 / 120

VigorSwitch G2080 User’s Guide 55
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The function, IGMP Snooping, is used to establish the multicast groups to forward the
multicast packet to the member ports, and, in nature, avoids wasting the bandwidth while
IP multicast packets are running over the network. This is because a switch that does not
support IGMP or IGMP Snooping can not tell the multicast packet from the broadcast
packet, so it can only treat them all as the broadcast packet. Without IGMP Snooping, the
multicast packet forwarding function is plain and nothing is different from broadcast
packet.
A switch supported IGMP Snooping with the functions of query, report and leave, a type of
packet exchanged between IP Multicast Router/Switch and IP Multicast Host, can update
the information of the Multicast table when a member (port) joins or leaves an IP Multicast
Destination Address. With this function, once a switch receives an IP multicast packet, it
will forward the packet to the members who joined in a specified IP multicast group before.
The packets will be discarded by the IGMP Snooping if the user transmits multicast
packets to the multicast group that had not been built up in advance.
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Function name:
IGMP Snooping
Function description:
IGMP is used to snoop the status of IP multicast groups and display its associated
information in both tagged VLAN and non-tagged VLAN networks. Enabling IGMP with
either passive or active mode, you can monitor the IGMP snooping information, which
contains the multicast member list with the multicast groups, VID and member port.
Parameter description:
Snooping Mode: The switch supports three kinds of IGMP Snooping status,
including “Passive”, “Active” and “Disable”.
Disable -
Set “Disable” mode to disable IGMP Snooping function.