Configuring Igmp Report Suppression - 3Com S7906E Configuration Manual

For devices that support both drop-unknown and igmp-snooping drop-unknown commands at
the same time, the configuration made in IGMP snooping view and the configuration made in VLAN
view are mutually exclusive. Namely, after this function is enabled in IGMP snooping view, it cannot
be enabled or disabled in VLAN view, and vice versa.
Configurations made in IGMP snooping view are effective for all VLANs, while configurations made
in VLAN view are effective only for ports belonging to the current VLAN.
If the function of dropping multicast packets is globally enabled in IGMP snooping view, multicast
packets sent to IGMP snooping-enabled VLANs are all dropped. The multicast packets mentioned
here include both multicast data packets and protocol packets, such as PIM, OSPF, and VRRP
messages.
After the function of dropping unknown multicast data packets is enabled in VLAN view, the switch
forwards unknown multicast data packets to its router ports, if any, instead of flooding them in the
VLAN. Otherwise, if no router ports exist, the switch drops these multicast data packets. Currently,
the S7900E supports processing unknown multicast data packets destined for up to 2000 unknown
multicast addresses at a time. The switch floods excessive unknown multicast data packets
directly.
The S7900E supports the function of dropping unknown multicast data packets configuring in up to
500 VLANs.

Configuring IGMP Report Suppression

When a Layer 2 device receives an IGMP report from a multicast group member, the device forwards
the message to the Layer 3 device directly connected with it. Thus, when multiple members of a
multicast group are attached to the Layer 2 device, the Layer 3 device directly connected with it will
receive duplicate IGMP reports from these members.
With the IGMP report suppression function enabled, within each query cycle, the Layer 2 device
forwards only the first IGMP report per multicast group to the Layer 3 device and will not forward the
subsequent IGMP reports from the same multicast group to the Layer 3 device. This helps reduce the
number of packets being transmitted over the network.
Follow these steps to configure IGMP report suppression:
To do...
Enter system view
Enter IGMP snooping view
Enable IGMP report
suppression
Use the command...
system-view
igmp-snooping
report-aggregation
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Remarks
—
—
Optional
Enabled by default