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17-10
Catalyst 2950 Desktop Switch Software Configuration Guide
78-14982-01
Chapter 17 Configuring IGMP Snooping and MVR
Configuring IGMP Snooping
If you disable IP multicast-source-only learning with 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. You should disable
IP multicast-source-only learning 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 to 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
Current configuration : 1972 bytes
!
version 12.1
no service pad
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname Switch
!
enable password my_password
!
ip subnet-zero
no ip igmp snooping source-only-learning
!
!
spanning-tree extend system-id
no spanning-tree vlan 1
!
!
interface FastEthernet0/1
no ip address
!
<output truncated>
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.