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Enabling dropping unknown multicast data
Unknown multicast data refers to multicast data for which no entries exist in the IGMP snooping
forwarding table. When the switch receives such multicast traffic, one of the following occurs:
•
When the function of dropping unknown multicast data is disabled, the switch floods unknown
multicast data in the VLAN that the unknown multicast data belongs to, causing network bandwidth
waste and low forwarding efficiency.
•
When the function of dropping unknown multicast data is enabled, the switch forwards unknown
multicast data to its router ports instead of flooding it in the VLAN. If no router ports exist, the switch
drops the unknown multicast data.
Configuration procedure
To enable dropping unknown multicast data globally:
Step Command
Remarks
1.
Enter system view.
system-view
N/A
2.
Enter IGMP-snooping view.
igmp-snooping
N/A
3.
Enable dropping unknown
multicast data.
drop-unknown
Disabled by default
Configuring IGMP report suppression
When a Layer 2 switch receives an IGMP report from a multicast group member, the switch forwards the
message to the Layer 3 device that directly connects to the Layer 2 switch. When multiple members of a
multicast group are attached to the Layer 2 switch, the Layer 3 device might receive duplicate IGMP
reports for the multicast group from these members.
With the IGMP report suppression function enabled, within each query interval, the Layer 2 switch
forwards only the first IGMP report for the multicast group to the Layer 3 device. It does not forward the
subsequent IGMP reports for the same multicast group. This helps reduce the number of packets being
transmitted over the network.
IMPORTANT:
On an IGMP snooping proxy, IGMP membership reports are suppressed if the entries for the
corresponding groups exist in the forwarding table, no matter the suppression function is enabled or not.
To configure IGMP report suppression:
Step Command
Remarks
1.
Enter system view.
system-view
N/A
2.
Enter IGMP-snooping view.
igmp-snooping
N/A
3.
Enable IGMP report
suppression.
report-aggregation
Enabled by default
