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
The following describes the fast convergence feature.
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 Dell Networking OS 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
396 Internet Group Management Protocol (IGMP)