Draytek VigorSwitch G2240, Руководство пользователя, Страница: 131 / 156

VigorSwitch G2240 User’s Guide 125
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The function is used 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 Mode
Function description:
IGMP mode enables the switch to issue IGMP function that you enable IGMP proxy or
snooping on the switch, which connects to a router closer to the root of the tree. This
interface is the
upstream interface . The router on the upstream interface should be running
IGMP.
Parameter description:
IGMP Mode: Scroll the IGMP mode with “Disable” , “Proxy” or
“Snooping”.