Administrator 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-specic query out of the ports specied 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. The last member query interval is the maximum response time inserted into Group-Specic
queries sent in response to Group-Leave messages.
• Sets the last member query interval in milliseconds on the specied VLAN.
INTERFACE VLAN mode
ip igmp snooping last-member-query-interval milliseconds
milliseconds — Enter the interval in milliseconds. The range is from 100 to 65535. The default is 1000 milliseconds.
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 trac 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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