MicroNet Technology SP1659P - Manual (Page 26)

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”.
3.8 IGMP Snooping
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.
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:
y IGMP snooping mode selection:
The switch supports three kinds of IGMP Snooping status, including “Passive”, “Active” and “Disable”.
Disable:
Set “Disable” mode to disable IGMP Snooping function.
Default: Disable
Active:
In Active mode, IGMP snooping switch will periodically issue the Membership Query message to all
hosts attached to it and gather the Membership report message to update the database of the
Multicast table. By the way, this also reduces the unnecessary multicast traffic.
Passive:
In Passive Snooping mode, the IGMP snooping will not periodically poll the hosts in the groups. The
switch will send a Membership Query message to all hosts only when it has received a Membership
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