Concept Guide

Table Of Contents
no ip igmp snooping flood
Specifying a Port as Connected to a Multicast Router
To statically specify or view a port in a VLAN, use the following commands.
Statically specify a port in a VLAN as connected to a multicast router.
INTERFACE VLAN mode
ip igmp snooping mrouter interface interface
For a 10-Gigabit Ethernet interface, enter the keyword TenGigabitEthernet then the slot/port information.
For a 40-Gigabit Ethernet interface, enter the keyword fortyGigE then the slot/port information.
For a Port Channel interface, enter the keywords portchannel then a number.
View the ports that are connected to multicast routers.
EXEC Privilege mode.
show ip igmp snooping mrouter
Configuring the Switch as Querier
To configure the switch as a querier, use the following command.
Hosts that do not support unsolicited reporting wait for a general query before sending a membership report. When the
multicast source and receivers are in the same VLAN, multicast traffic is not routed and so there is no querier. Configure the
switch to be the querier for a VLAN so that hosts send membership reports and the switch can generate a forwarding table by
snooping.
Configure the switch to be the querier for a VLAN by first assigning an IP address to the VLAN interface.
INTERFACE VLAN mode
ip igmp snooping querier
IGMP snooping querier does not start if there is a statically configured multicast router interface in the VLAN.
The switch may lose the querier election if it does not have the lowest IP address of all potential queriers on the subnet.
When enabled, IGMP snooping querier starts after one query interval in case no IGMP general query (with IP SA lower than
its VLAN IP address) is received on any of its VLAN members.
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. The last member query interval is the maximum
response time inserted into Group-Specific queries sent in response to Group-Leave messages.
Sets the last member query interval in milliseconds on the specified 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.
Internet Group Management Protocol (IGMP)
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