Disabling Ip Multicast-Source-Only Learning - Cisco Catalyst 2950 Software Configuration Manual

Chapter 20 Configuring IGMP Snooping and MVR

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.
We strongly recommend that you do not disable IP multicast-source-only learning. IP
Note
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:
Command
Step 1 configure terminal
Step 2
no ip igmp snooping source-only-learning
Step 3 no ip igmp snooping mrouter learn pim v2
Step 4 end
Step 5 show running-config | include
source-only-learning
Step 6
copy running-config startup-config
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
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Purpose
Enter global configuration mode
Disable IP multicast-source-only learning.
(Optional) Disable multicast router discovery by PIM v2
packets.
Return to privileged EXEC mode.
Verify that IP multicast-source-only learning is disabled.
(Optional) Save your entries in the configuration file.
Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
Configuring IGMP Snooping
20-13