3com 4210 PWR 9-Port 3CR17341-91-ME ユーザーズマニュアル

C

HAPTER

 16: IGMP S

NOOPING

 C

ONFIGURATION

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.

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. 

Configure dropping unknown multicast packet

Enter system view

-

Configure dropping 
unknown multicast packets

Required

By default, the function of dropping 
unknown multicast packets is disabled.