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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 forwards multicast traffic destined for multicast groups (that it has learned from
IGMP snooping or that you have manually configured) to ports that are members of that group.
IGMP snooping generates no additional network traffic, allowing you to significantly reduce
multicast traffic passing through your Switch.
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
removed from multicast group membership.
IGMP Querier
There is normally only one Querier per physical network. All multicast routers start up as a
Querier on each attached network. If a multicast router hears a Query message from a router
with
a lower IP address
, it MUST become a Non-Querier on that network. If a router has not heard a
Query message from another router for [Other Querier Present Interval], it resumes the role of
Querier. Routers periodically [Query Interval] send a General Query on each attached network
