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Chapter 21
Configuring IGMP Snooping
Beginning in privileged EXEC mode, follow these steps to globally enable IGMP snooping on the
switch:
Command
Step 1
configure terminal
Step 2
ip igmp snooping
Step 3
end
Step 4
copy running-config startup-config
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:
Command
Step 1
configure terminal
Step 2
ip igmp snooping vlan vlan-id
Step 3
end
Step 4
copy running-config startup-config
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:
•
•
•
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 to 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.
OL-23389-01
Purpose
Enter global configuration mode.
Globally enable IGMP snooping in all existing VLAN interfaces.
Return to privileged EXEC mode.
(Optional) Save your entries in the configuration file.
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
Purpose
Enter global configuration mode.
Enable IGMP snooping on the VLAN interface.The VLAN ID range
is 1 to 1001 and 1006 to 4094.
IGMP snooping must be globally enabled before you can
Note
enable VLAN snooping.
Return to privileged EXEC mode.
(Optional) Save your entries in the configuration file.
Catalyst 2928 Switch Software Configuration Guide
Configuring IGMP Snooping
21-7
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