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Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
OL-10101-02
Chapter 20 Configuring IGMP Snooping and MVR
Configuring IGMP Snooping
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 no 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.
To disable multicast router discovery by PIMv2 packets, you should also enter the no ip igmp snooping
mrouter learn pim v2 global configuration command.
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. To enable PIM v2 multicast router discovery, use the p igmp snooping
mrouter learn pim v2 global configuration command.
This example shows how to disable IP multicast-source-only learning and PIM v2 multicast router
discovery:
Switch# configure terminal
Switch(config)# no ip igmp snooping source-only-learning
Switch(config)# no ip igmp snooping mrouter learn pim v2
Switch(config)# end
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
no ip igmp snooping mrouter learn pim v2 (Optional) Disable multicast router discovery by PIM v2
packets.
Step 4
end Return to privileged EXEC mode.
Step 5
show running-config | include
source-only-learning
Verify that IP multicast-source-only learning is disabled.
Step 6
copy running-config startup-config (Optional) Save your entries in the configuration file.