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17-6
Catalyst 2950 Desktop Switch Software Configuration Guide
78-14982-01
Chapter 17 Configuring IGMP Snooping and MVR
Configuring IGMP Snooping
Beginning in privileged EXEC mode, follow these steps to globally enable IGMP snooping on the
switch:
To globally disable IGMP snooping on all VLAN interfaces, use the no ip igmp snooping global
configuration command.
Beginning in privileged EXEC mode, follow these steps to enable IGMP snooping on a VLAN interface:
To disable IGMP snooping on a VLAN interface, use the no ip igmp snooping vlan vlan-id global
configuration command for the specified VLAN number.
Setting the Snooping Method
Multicast-capable router ports are added to the forwarding table for every Layer 2 multicast entry. The
switch learns of such ports through one of these methods:
• Snooping on IGMP queries, Protocol Independent Multicast (PIM) packets, and Distance Vector
Multicast Routing Protocol (DVMRP) packets
• Listening to Cisco Group Management Protocol (CGMP) packets from other routers
• Statically connecting to a multicast router port with the ip igmp snooping mrouter global
configuration command
You can configure the switch either to snoop on IGMP queries and PIM/DVMRP packets or to listen to
CGMP self-join or proxy-join packets. By default, the switch snoops on PIM/DVMRP packets on all
VLANs. To learn of multicast router ports through only CGMP packets, use the ip igmp snooping vlan
vlan-id mrouter learn cgmp global configuration command. When this command is entered, the router
listens to only CGMP self-join and CGMP proxy-join packets and no other CGMP packets. To learn of
multicast router ports through only PIM-DVMRP packets, use the ip igmp snooping vlan vlan-id
mrouter learn pim-dvmrp global configuration command.
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
ip igmp snooping Globally enable IGMP snooping in all existing VLAN interfaces.
Step 3
end Return to privileged EXEC mode.
Step 4
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
ip igmp snooping vlan vlan-id Enable IGMP snooping on the VLAN interface.
Step 3
end Return to privileged EXEC mode.
Step 4
copy running-config startup-config (Optional) Save your entries in the configuration file.