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VigorSwitch P2260 User’s Guide
49
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The DHCP Boot function is used to spread the request broadcast packet into a bigger time
frame to prevent the traffic congestion due to broadcast packets from many network
devices which may seek its NMS, boot server, DHCP server and many connections
predefined when the whole building or block lose the power and then reboot and recover.
At this moment, a bunch of switch or other network device on the LAN will try its best to
find the server to get the services or try to set up the predefined links, they will issue many
broadcast packets in the network.
The switch supports a random delay time for DHCP and boot delay for each device. This
suppresses the broadcast storm while all devices are at booting stage in the same time. The
maximum user-defined delay time is 30 sec. If DHCP Broadcasting Suppression function is
enabled, the delay time is set randomly, ranging from 0 to 30 seconds, because the exactly
delay time is computed by the switch itself. The default is “Disable”.
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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: