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Catalyst 6500 Series Switch Software Configuration Guide—Release 8.7
OL-8978-04
Chapter 51 Configuring Multicast Services
Configuring IGMP Snooping on the Switch
IGMP Snooping Configuration Guidelines
This section describes the IGMP snooping configuration guidelines:
• There is no proxy reporting support with IGMP version 3 snooping. With IGMP version 2 snooping,
only the first join and the last leave are forwarded to the router. For the group-specific (GS) queries
that are initiated by the router, the switch responds with a report if at least one port is present for the
group. With IGMP version 3 snooping, all reports are forwarded to the router, and the GS, group,
and source-specific (GSS) queries are flooded onto the VLAN to refresh the memberships.
• At least one version 3 router must be present on the VLAN for IGMP version 3 snooping to work.
• Unlike IGMP version 2 snooping, for IGMP version 3 snooping, no permanent entries can be added
that would be retained across reboots.
• IGMP version 2 snooping reports are captured and sent to the supervisor engine. The IGMP
version 3 snooping reports are sent to the 224.0.0.22 address. Because snooping is not supported in
this range, the reports are captured for the supervisor engine in addition to being flooded.
• With this release of IGMP version 3 snooping, the RGMP, SPAN, and RSPAN interaction is not
enabled.
• IGMP querier interoperates only with IGMP version 2 snooping. Before you enable IGMP version 3
snooping, you must disable IGMP querier.
Enabling IGMP Snooping
Note You cannot enable IGMP snooping if GMRP is enabled.
To enable IGMP snooping, perform this task in privileged mode:
This example shows how to enable IGMP snooping and verify the configuration:
Console> (enable) set igmp enable
IGMP Snooping is enabled.
Console> (enable) show igmp statistics
IGMP enabled
IGMP statistics for vlan 1:
Transmit:
General Queries: 0
Group Specific Queries: 0
Reports: 0
Leaves: 0
Receive:
General Queries: 1056
Group Specific Queries: 0
Group and Source Specific Queries: 2
Reports: 60379
Leaves: 0
Task Command
Step 1
Enable IGMP snooping. set igmp enable
Step 2
Verify that IGMP snooping is enabled. show igmp statistics [vlan]
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