Users Guide

Layer 2 Switching Commands 515
and thus not detectable by the switch. If a query is not received on an
interface within a specified length of time (multicast router present
expiration time), that interface is removed from the list of interfaces with
multicast routers attached. The multicast router present expiration time is
configurable using management. The default value for the multicast router
expiration time is zero, which indicates an infinite time-out (that is, no
expiration).
ip igmp snooping
Use the ip igmp snooping command in Global Configuration mode without
parameters to globally enable Internet Group Management Protocol (IGMP)
snooping. Use the vlan form of the command to enable IGMP snooping on a
specific VLAN. Use the no form of this command to disable IGMP snooping
globally.
Syntax
ip igmp snooping [vlan vlan-id]
no ip igmp snooping [vlan vlan-id]
• vlan-id —Specifies a VLAN ID value.
Default Configuration
IGMP snooping is enabled globally and on all VLANs by default.
Command Mode
Global Configuration mode
User Guidelines
Use this command without parameters to globally enable IGMP snooping.
Use the no form of the command to disable IGMP snooping. Use the vlan
parameter to enable IGMP snooping on a specific VLAN. GMRP is
incompatible with IGMP snooping and should be disabled on any VLANs on
which IGMP snooping is enabled. It is recommended that MLD snooping
should be enabled whenever IGMP snooping is enabled to ensure that
unwanted pruning of multicast protocol packets used by other protocols does
not occur.