17-10
Catalyst 2950 Desktop Switch Software Configuration Guide
78-14982-01
Chapter 17 Co nfiguring IGMP S noo ping and M VR
Configuring IG MP 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 traff ic 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 recomme nd that you do not disable IP multicast-sour ce-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 disab l ing th is lea rni ng me thod i mproves th e ne twork perf orm a nce.
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
configurati on comm a nd.
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 globa l configurati on mode
Step 2 no ip igmp snooping source-only-learning Disable IP multic ast-sourc e-only learn ing.
Step 3 end Return to privileged EXEC mode.
Step 4 show running-config | include
source-only-learning Verify tha t I P m ultic ast -sourc e-onl y learn ing i s disa ble d.
Step 5 copy running-config startup-config (Optiona l) Save your entries in the co nfigurati on file.