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Catalyst 3750-X and 3560-X Switch Software Configuration Guide
OL-25303-03
Chapter 1 Configuring IGMP Snooping and MVR
Configuring IGMP Snooping
To re-enable multicast flooding on an interface, use the ip igmp snooping tcn flood interface
configuration command.
Configuring the IGMP Snooping Querier
Follow these guidelines when configuring the IGMP snooping querier:
• Configure the VLAN in global configuration mode.
• Configure an IP address on the VLAN interface. When enabled, the IGMP snooping querier uses the
IP address as the query source address.
• If there is no IP address configured on the VLAN interface, the IGMP snooping querier tries to use
the configured global IP address for the IGMP querier. If there is no global IP address specified, the
IGMP querier tries to use the VLAN switch virtual interface (SVI) IP address (if one exists). If there
is no SVI IP address, the switch uses the first available IP address configured on the switch. The first
IP address available appears in the output of the show ip interface privileged EXEC command. The
IGMP snooping querier does not generate an IGMP general query if it cannot find an available IP
address on the switch.
• The IGMP snooping querier supports IGMP Versions 1 and 2.
• When administratively enabled, the IGMP snooping querier moves to the nonquerier state if it
detects the presence of a multicast router in the network.
• When it is administratively enabled, the IGMP snooping querier moves to the operationally disabled
state under these conditions:
–
IGMP snooping is disabled in the VLAN.
–
PIM is enabled on the SVI of the corresponding VLAN.
Beginning in privileged EXEC mode, follow these steps to enable the IGMP snooping querier feature in
a VLAN:
Step 3
no ip igmp snooping tcn flood Disable the flooding of multicast traffic during a spanning-tree TCN
event.
By default, multicast flooding is enabled on an interface.
Step 4
exit Return to privileged EXEC mode.
Step 5
show ip igmp snooping Verify the TCN settings.
Step 6
copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
ip igmp snooping querier Enable the IGMP snooping querier.
Step 3
ip igmp snooping querier address
ip_address
(Optional) Specify an IP address for the IGMP snooping querier. If
you do not specify an IP address, the querier tries to use the global IP
address configured for the IGMP querier.
Note The IGMP snooping querier does not generate an IGMP
general query if it cannot find an IP address on the switch.
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