Users Guide

When the IGMP querier receives a leave message, it sends a group-specific query message to ensure if any other host in the
network is interested in the multicast flow. By default, the group-specific query messages are sent every 1000 milliseconds. You
can configure this value using the ip igmp last-member-query-interval command.
To configure last member query interval:
OS10# configure terminal
OS10# interface vlan120
OS10(conf-if-vl-120)# ip igmp last-member-query-interval 200
Maximum response time
The maximum response time is the amount of time that the querier waits for a response to a query before taking action.
When a host receives a query, it does not respond immediately, but rather starts a delay timer. The delay time is set to a random
value between 0 and the maximum response time. The host sends a response when the timer expires; in IGMP version 2, if
another host responds before the timer expires, the timer nullifies, and no response is sent.
The querier advertises the maximum response time in the query. Lowering this value decreases leave latency but increases
response burstiness because all host membership reports are sent before the maximum response time expires. Inversely,
increasing this value decreases burstiness, but increases leave latency.
To configure maximum response time:
OS10# configure terminal
OS10# interface vlan120
OS10(conf-if-vl-120)# ip igmp query-max-resp-time 20
IGMP immediate leave
If the IGMP querier does not receive a response to a group-specific or group-and-source query, it sends another query based on
the configured querier robustness value. This value determines the number of times the querier sends the message. If the
querier does not receive a 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. Immediate leave does not send group-specific or group-and-source queries before deleting the
entry.
To configure IGMP immediate leave:
OS10# configure terminal
OS10# interface vlan14
OS10(conf-if-vl-14)# ip igmp immediate-leave
Select an IGMP version
OS10 enables IGMP version 3 by default.
If hosts require an IGMP version other than 3, use the following to select a different IGMP version:
OS10# configure terminal
OS10# interface vlan12
OS10(conf-if-vl-12)# ip igmp version 3
View IGMP-enabled interfaces and groups
To view IGMP-enabled interfaces and groups, use the following show commands.
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Multicast