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16-11
Catalyst 2940 Switch Software Configuration Guide
78-15507-02
Chapter 16 Configuring IGMP Snooping and MVR
Configuring IGMP Snooping
Beginning in privileged EXEC mode, follow these steps to disable IGMP report suppression:
To re-enable IGMP report suppression, use the ip igmp snooping report-suppression global
configuration command.
Disabling IP Multicast-Source-Only Learning
The IP multicast-source-only learning method is enabled by default. The switch learns the IP multicast
group from the IP multicast data stream and only forwards traffic to the multicast router ports.
If IP multicast-source-only learning is disabled by using the ip igmp snooping source-only-learning
global configuration command, the switch floods unknown multicast traffic to the VLAN and sends the
traffic to the CPU until the traffic becomes known. When the switch receives an IGMP report from a host
for a particular multicast group, the switch forwards traffic from this multicast group only to the
multicast router ports.
Note We strongly recommend that you do not disable IP multicast-source-only learning. IP
multicast-source-only learning should be disabled only if your network is not composed of IP
multicast-source-only networks and if disabling this learning method improves the network
performance.
Beginning in privileged EXEC mode, follow these steps to disable IP multicast-source-only learning:
To enable IP multicast-source-only learning, use the ip igmp snooping source-only-learning global
configuration command.
This example shows how to disable IP multicast-source-only learning and verify the configuration:
Switch# configure terminal
Switch(config)# no ip igmp snooping source-only-learning
Switch(config)# end
Switch# show running-config | include source-only-learning
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.
Command Purpose
Step 1
configure terminal Enter global configuration mode
Step 2
no ip igmp snooping source-only-learning Disable IP multicast-source-only learning.
Step 3
end Return to privileged EXEC mode.
Step 4
show running-config | include
source-only-learning
Verify that IP multicast-source-only learning is disabled.
Step 5
copy running-config startup-config (Optional) Save your entries in the configuration file.