Deployment Guide

Table Of Contents
When the querier receives a leave message from a host, it sends a group-specific query to the subnet. 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 from the state table.
Adjust the period between queries.
INTERFACE mode
ip igmp query-interval
Adjust the time period between queries used to discover IPv6 multicast groups.
Interface mode
ipv6 mld query-interval
Adjust the maximum response time.
INTERFACE mode
ip igmp query-max-resp-time
Adjust the maximum amount of time that the querier waits, for an IPv6 query response, before taking further action.
Interface mode
ipv6 mld query-max-response-time
Adjust the last member query interval.
INTERFACE mode
ip igmp last-member-query-interval
Adjust the amount of time the querier waits, for the initial query response, before sending the next IPv6 query.
Interface mode
ipv6 mld last-member-query-interval
Enabling IGMP Immediate-Leave
If the querier does not receive a response to a group-specific or group-and-source query, it sends another (querier robustness
value). Then, after no response, it removes the group from the outgoing interface for the subnet.
IGMP immediate leave reduces leave latency by enabling a router to immediately delete the group membership on an interface
after receiving a Leave message (it does not send any group-specific or group-and-source queries before deleting the entry).
Configure the system for IGMP immediate leave.
ip igmp immediate-leave
Configure the system to immediately delete the IPv6 group membership on an interface after receiving a leave message.
ipv6 mld immediate-leave
View the enable status of the IGMP immediate leave feature.
EXEC Privilege mode
show ip igmp interface
show ipv6 mld interface
View the enable status of this feature using the command from EXEC Privilege mode, as shown in the example in Selecting an
IGMP Version.
IGMP Snooping
IGMP snooping enables switches to use information in IGMP packets to generate a forwarding table that associates ports with
multicast groups so that when they receive multicast frames, they can forward them only to interested receivers.
Multicast packets are addressed with multicast MAC addresses, which represent a group of devices, rather than one unique
device. Switches forward multicast frames out of all ports in a virtual local area network (VLAN) by default, even though there
may be only some interested hosts, which is a waste of bandwidth.
If you enable IGMP snooping on a VLT unit, IGMP snooping dynamically learned groups and multicast router ports are made to
learn on the peer by explicitly tunneling the received IGMP control packets.
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Internet Group Management Protocol (IGMP)