IGMP Report Suppression
IGMP report suppression is supported only when the multicast query has IGMPv1 and IGMPv2 reports.
This feature is not supported when the query includes IGMPv3 reports.
Note
The switch uses IGMP report suppression to forward only one IGMP report per multicast router query to
multicast devices. When IGMP report suppression is enabled (the default), the switch sends the first IGMP
report from all hosts for a group to all the multicast routers. The switch does not send the remaining IGMP
reports for the group to the multicast routers. This feature prevents duplicate reports from being sent to the
multicast devices.
If the multicast router query includes requests only for IGMPv1 and IGMPv2 reports, the switch forwards
only the first IGMPv1 or IGMPv2 report from all hosts for a group to all the multicast routers.
If the multicast router query also includes requests for IGMPv3 reports, the switch forwards all IGMPv1,
IGMPv2, and IGMPv3 reports for a group to the multicast devices.
If you disable IGMP report suppression, all IGMP reports are forwarded to the multicast routers.
Related Topics
Disabling IGMP Report Suppression , on page 145
IGMP Snooping and Switch Stacks
IGMP snooping functions across the switch stack; that is, IGMP control information from one switch is
distributed to all switches in the stack. Regardless of the stack member through which IGMP multicast data
enters the stack, the data reaches the hosts that have registered for that group.
If a switch in the stack fails or is removed from the stack, only the members of the multicast group that are
on that switch will not receive the multicast data. All other members of a multicast group on other switches
in the stack continue to receive multicast data streams. However, multicast groups that are common for both
Layer 2 and Layer 3 (IP multicast routing) might take longer to converge if the active switch is removed.
Default IGMP Snooping Configuration
This table displays the default IGMP snooping configuration for the switch.
Table 15: Default IGMP Snooping Configuration
Default Setting
Feature
Enabled globally and per VLAN
IGMP snooping
None configured
Multicast routers
Disabled
IGMP snooping Immediate Leave
None configured
Static groups
2
TCN
flood query count
Consolidated Platform Configuration Guide, Cisco IOS Release 15.2(4)E (Catalyst 2960-X Switches)
122
Information About IGMP Snooping and MVR
Summary of Contents for Catalyst 2960 Series
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