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21-6
Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
OL-9639-06
Chapter 21 Configuring IGMP Snooping and MVR
Configuring IGMP Snooping
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 21-14.
Configuring IGMP Snooping
IGMP snooping allows switches to examine IGMP packets and make forwarding decisions based on their
content. These sections contain this configuration information:
• Default IGMP Snooping Configuration, page 21-6
• Enabling or Disabling IGMP Snooping, page 21-7
• Configuring a Multicast Router Port, page 21-7
• Configuring a Host Statically to Join a Group, page 21-8
• Enabling IGMP Immediate Leave, page 21-9
• Configuring the IGMP Leave Timer, page 21-9
• Configuring TCN-Related Commands, page 21-10
• Configuring the IGMP Snooping Querier, page 21-12
• Disabling IGMP Report Suppression, page 21-14
Default IGMP Snooping Configuration
Table 21-3 shows the default IGMP snooping configuration.
Ta ble 21-3 Default IGMP Snooping Configuration
Feature Default Setting
IGMP snooping Enabled globally and per VLAN
Multicast routers None configured
Multicast router learning (snooping) method PIM
IGMP snooping Immediate Leave Disabled
Static groups None configured
TCN
1
flood query count
1. TCN = Topology Change Notification
2
TCN query solicitation Disabled
IGMP snooping querier Disabled
IGMP report suppression Enabled