Cisco Catalyst 3750 Software Configuration Manual page 343

Chapter 17 Configuring IGMP Snooping and MVR
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.
If you want to use CGMP as the learning method and no multicast routers in the VLAN are CGMP
Note
proxy-enabled, you must enter the ip cgmp router-only command to dynamically access the router. For
more information, see
Beginning in privileged EXEC mode, follow these steps to alter the method in which a VLAN interface
dynamically accesses a multicast router:
Command
Step 1 configure terminal
Step 2 ip igmp snooping vlan vlan-id mrouter
learn {cgmp | pim-dvmrp}
Step 3
end
Step 4 show ip igmp snooping
Step 5 copy running-config startup-config
This example shows how to configure IGMP snooping to use CGMP packets as the learning method and
verify the configuration:
Switch# configure terminal
Switch(config)# ip igmp snooping vlan 1 mrouter learn cgmp
Switch(config)# end
Switch# show ip igmp snooping vlan 1
vlan 1
----------
IGMP snooping is globally enabled
IGMP snooping is enabled on this Vlan
IGMP snooping immediate-leave is disabled on this Vlan
IGMP snooping mrouter learn mode is cgmp on this Vlan
IGMP snooping is running in IGMP_ONLY mode on this Vlan
To return to the default learning method, use the no ip igmp snooping vlan vlan-id mrouter learn cgmp
global configuration command.
78-15870-01
Chapter 31, "Configuring IP Multicast Routing."
Purpose
Enter global configuration mode.
Enable IGMP snooping on a VLAN.The VLAN ID range is 1 to 4094.
Specify the multicast router learning method:
cgmp—Listen for CGMP packets. This method is useful for
•
reducing control traffic.
• pim-dvmrp—Snoop on IGMP queries and PIM-DVMRP packets.
This is the default.
Return to privileged EXEC mode.
Verify the configuration.
(Optional) Save your entries in the configuration file.
Catalyst 3750 Metro Switch Software Configuration Guide
Configuring IGMP Snooping
17-7