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Catalyst 2940 Switch Software Configuration Guide
78-15507-02
Chapter 16 Configuring IGMP Snooping and MVR
Configuring IGMP Snooping
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.
Beginning in privileged EXEC mode, follow these steps to alter the method in which a VLAN interface
dynamically accesses a multicast router:
This example shows how to configure IGMP snooping to use CGMP packets as the learning method:
Switch# configure terminal
Switch(config)# ip igmp snooping vlan 1 mrouter learn cgmp
Switch(config)# end
Switch# show ip igmp snooping vlan 1
Global IGMP Snooping configuration:
-----------------------------------
IGMP snooping :Enabled
IGMPv3 snooping (minimal) :Enabled
Report suppression :Enabled
TCN solicit query :Disabled
TCN flood query count :2
Vlan 1:
--------
IGMP snooping :Enabled
Immediate leave :Disabled
Multicast router learning mode :pim-dvmrp
Source only learning age timer :10
CGMP interoperability mode :IGMP_ONLY
To return to the default learning method, use the no ip igmp snooping vlan vlan-id mrouter learn cgmp
global configuration command.
Configuring a Multicast Router Port
To add a multicast router port (add a static connection to a multicast router), use the ip igmp snooping
vlan mrouter global configuration command on the switch.
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
ip igmp snooping vlan vlan-id mrouter
learn {cgmp | pim-dvmrp}
Enable IGMP snooping on a VLAN.The VLAN ID range is 1 to 1005.
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.
Step 3
end Return to privileged EXEC mode.
Step 4
show ip igmp snooping Verify the configuration.
Step 5
copy running-config startup-config (Optional) Save your entries in the configuration file.