210 CHAPTER 16: IGMP SNOOPING CONFIGURATION
Troubleshooting IGMP
Snooping
Symptom: Multicast function does not work on the switch.
Solution: Possible reasons are:
■ IGMP Snooping is not enabled.
■ Use the display current-configuration command to check the status of IGMP
Snooping.
■ If IGMP Snooping is disabled, check whether it is disabled globally or in the
specific VLAN. If it is disabled globally, use the igmp-snooping enable
command in both system view and VLAN view to enable it both globally
and on the corresponding VLAN at the same time. If it is only disabled on
the corresponding VLAN, use the igmp-snooping enable command in VLAN
view only to enable it on the corresponding VLAN.
■ Multicast forwarding table set up by IGMP Snooping is wrong.
■ Use the display igmp-snooping group command to check if the multicast
groups are expected ones.
■ If the multicast group set up by IGMP Snooping is not correct, contact your
technical support personnel.
Configuring Dropping
Unknown Multicast
Packets
Generally, if the multicast address of the multicast packet received on the switch is
not registered on the local switch, the packet will be flooded in the VLAN. When
the function of dropping unknown multicast packets is enabled, the switch will
drop any multicast packets whose multicast address is not registered. Thus, the
bandwidth is saved and the processing efficiency of the system is improved.
Tabl e 161 Configure dropping unknown multicast packet
Operation Command Remarks
Enter system view system-view -
Configure dropping
unknown multicast packets
unknown-multica
st drop enable
Required
By default, the function of dropping
unknown multicast packets is disabled.
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