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20-7
Catalyst 3550 Multilayer Switch Software Configuration Guide
78-11194-09
Chapter 20 Configuring IGMP Snooping and MVR
Configuring IGMP Snooping
Enabling or Disabling IGMP Snooping
By default, IGMP snooping is globally enabled on the switch. When globally enabled or disabled, it is
also enabled or disabled in all existing VLAN interfaces. IGMP snooping is by default enabled on all
VLANs, but can be enabled and disabled on a per-VLAN basis. After you configure the VLAN interface
for multicast routing, no configuration is needed for the switch to dynamically access external multicast
routers by using IGMP snooping.
Global IGMP snooping overrides the VLAN IGMP snooping. If global snooping is disabled, you cannot
enable VLAN snooping. If global snooping is enabled, you can enable or disable VLAN 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.
Aging forward-table entries (for traffic that aliases
with reserved, destination, multicast IP addresses)
Enabled. The default is 600 seconds
(10 minutes).
IGMP report suppression
Enabled.
Table 20-3 Default IGMP Snooping Configuration (continued)
Feature
Default Setting
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.