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20-11
Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
OL-10101-02
Chapter 20 Configuring IGMP Snooping and MVR
Configuring IGMP Snooping
• The default leave time is 1000 milliseconds.
• The IGMP configurable leave time is only supported on hosts running IGMP Version 2.
• The actual leave latency in the network is usually the configured leave time. However, the leave time
might vary around the configured time, depending on real-time CPU load conditions, network delays
and the amount of traffic sent through the interface.
Beginning in privileged EXEC mode, follow these steps to enable the IGMP configurable-leave timer:
Use the no ip igmp snooping last-member-query-interval global configuration command to globally
reset the IGMP leave timer to the default setting (1000 milliseconds).
Use the no ip igmp snooping vlan vlan-id last-member-query-interval global configuration
command to remove the configured IGMP leave-time setting from the specified VLAN.
Disabling IGMP Report Suppression
IGMP report suppression is enabled by default. When it is enabled, the switch forwards only one IGMP
report per multicast router query. When report suppression is disabled, all IGMP reports are forwarded
to the multicast routers.
Note IGMP report suppression is supported only when the multicast query has IGMPv1 and IGMPv2 reports.
This feature is not supported when the query includes IGMPv3 reports.
Beginning in privileged EXEC mode, follow these steps to disable IGMP report suppression:
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
ip igmp snooping
last-member-query-interval time
Configure the IGMP leave timer globally. The range is 100 to 5000
milliseconds.
Step 3
ip igmp snooping vlan vlan-id
last-member-query-interval time
(Optional) Configure the IGMP leave time on the VLAN interface. The
range is 100 to 5000 milliseconds.
Note Configuring the leave time on a VLAN overrides the globally
configured timer.
Step 4
end Return to privileged EXEC mode.
Step 5
show ip igmp snooping (Optional) Display the configured IGMP leave time.
Step 6
copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
no ip igmp snooping report-suppression Disable IGMP report suppression.
Step 3
end Return to privileged EXEC mode.
Step 4
show ip igmp snooping Verify that IGMP report suppression is disabled.
Step 5
copy running-config startup-config (Optional) Save your entries in the configuration file.