Reference Guide

Adjusting the Last Member Query Interval
To adjust the last member query interval, use the following command.
When the querier receives a Leave message from a receiver, it sends a group-specific query out of the ports specified in the
forwarding table. If no response is received, it sends another. The amount of time that the querier waits to receive a response to
the initial query before sending a second one is the last member query interval (LMQI). The switch waits one LMQI after the
second query before removing the group-port entry from the forwarding table.
● Adjust the last member query interval.
INTERFACE VLAN mode
ip igmp snooping last-member-query-interval
Fast Convergence after MSTP Topology Changes
When a port transitions to the Forwarding state as a result of an STP or MSTP topology change, the system sends a general
query out of all ports except the multicast router ports. The host sends a response to the general query and the forwarding
database is updated without having to wait for the query interval to expire.
When an IGMP snooping switch is not acting as a querier, it sends out the general query in response to the MSTP triggered link-
layer topology change, with the source IP address of 0.0.0.0 to avoid triggering querier election.
Designating a Multicast Router Interface
To designate an interface as a multicast router interface, use the following command.
The system also has the capability of listening in on the incoming IGMP general queries and designate those interfaces as the
multicast router interface when the frames have a non-zero IP source address. All IGMP control packets and IP multicast data
traffic originating from receivers is forwarded to multicast router interfaces.
● Designate an interface as a multicast router interface.
ip igmp snooping mrouter interface
Internet Group Management Protocol (IGMP)
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