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Cisco IE 2000 Switch Software Configuration Guide
OL-25866-01
Chapter 28 Configuring IGMP Snooping and MVR
Information About IGMP Snooping and MVR
IGMP Report Suppression
Note 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.
The switch uses IGMP report suppression to forward only one IGMP report per multicast router query
to multicast devices. When IGMP router 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. For
configuration steps, see the “Disabling IGMP Report Suppression” section on page 28-16.
Default IGMP Snooping Configuration
Table 28-3 shows the default IGMP snooping configuration.
Snooping Methods
Multicast-capable router ports are added to the forwardi ng table for every Layer 2 multicast entry. The
switch learns of such ports through one of these methods:
Snooping on IGMP queries, Protocol Independent Multicast (PIM) packets, and Distance Vector
Multicast Routing Protocol (DVMRP) packets
��� Listening to Cisco Group Management Protocol (CGMP) packets from other routers
Statically connecting to a multicast router port with the ip igmp snooping mrouter global
configuration command
Tab l e 28-3 Default IGMP Snooping Configuration
Feature Default Setting
IGMP snooping Enabled globally and per VLAN
Multicast routers None configured
Multicast router learning (snooping) method PIM-DVMRP
IGMP snooping Immediate Leave Disabled
Static groups None configured
TCN1 flood query count
1. TCN = Topology Change Notification
2
TCN query solicitation Disabled
IGMP snooping querier Disabled
IGMP report suppression Enabled