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INSTALLATION AND OPERATION MANUAL
CWGE24MS2
TECH SUPPORT: 1.888.678.9427
IGMP Snooping
IGMP Snooping
Introduction
The IGMP snooping is for multicast traffic. The Switch can passively snoop on IGMP packets
transferred between IP multicast routers/switches and IP multicast hosts to learn the IP multicast group
membership. It checks IGMP packets passing through it, picks out the group registration information,
and configures multicasting accordingly. IGMP snooping allows the Switch to learn multicast groups
without you having to manually configure them.
The Switch can passively snoop on IGMP packets transferred between IP multicast routers/switches
and IP multicast hosts to learn the IP multicast group membership. It checks IGMP packets passing
through it, picks out the group registration information, and configures multicasting accordingly. IGMP
snooping allows the Switch to learn multicast groups without you having to manually configure them.
The Switch can perform IGMP snooping on up to 4094 VLANs. You can configure the Switch to
automatically learn multicast group membership of any VLANs. The Switch then performs IGMP
snooping on the first VLANs that send IGMP packets. Alternatively, you can specify the VLANs
that IGMP snooping should be performed on. This is referred to as fixed mode. In fixed mode
the Switch does not learn multicast group membership of any VLANs other than those explicitly
added as an IGMP snooping VLAN.
Immediate Leave
When you enable IGMP Immediate-Leave processing, the switch immediately removes a port
when it detects an IGMP version 2 leave message on that port. You should use the Immediate-
Leave feature only when there is a single receiver present on every port in the VLAN. (Immediate
Leave is only supported on IGMP Version 2 hosts).
The switch uses IGMP snooping Immediate Leave to remove from the forwarding table an
interface that sends a leave message without the switch sending group-specific queries to the
interface. The VLAN interface is pruned from the multicast tree for the multicast group specified
in the original leave message. Immediate Leave ensures optimal bandwidth management for all
hosts on a switched network, even when multiple multicast groups are simultaneously in use.
Fast Leave
The switch allow user to configure a delay time. When the delay time is expired, the switch
removes the interface from the multicast group.
Last Member Query Interval
Last Member Query Interval: The Last Member Query Interval is the Max Response Time inserted
into Group-Specific Queries sent in response to Leave Group messages, and is also the amount of
time between Group-Specific Query messages.
Without Immediate Leave, when the switch receives an IGMP leave message from a subscriber
on a receiver port, it sends out an IGMP specific query on that port and waits for IGMP group
membership reports. If no reports are received in a configured time period, the receiver port is
