3Com 4200G # Enable Igmp Snooping querier in Vlan, # Enable dropping unknown multicast packets

Configuring IGMP Snooping Only 139

[SwitchA] vlan 100

[SwitchA-vlan100] port Ethernet 1/0/1 Ethernet 1/0/2

[SwitchA-vlan100] igmp-snooping enable

# Enable IGMP Snooping querier in VLAN 100.

[SwitchA-vlan100] igmp-snooping querier

[SwitchA-vlan100] quit

# Enable dropping unknown multicast packets.

[SwitchA] unknown-multicast drop enable

Configuring Switch B

# Enable IGMP Snooping globally.

<SwitchB> system-view

[SwitchB] igmp-snooping enable

Enable IGMP-Snooping ok.

#Create VLAN 100, assign Ethernet 1/0/1 through Ethernet 1/0/3 to VLAN 100, and enable IGMP Snooping in this VLAN.

[SwitchB] vlan 100

[SwitchB-vlan100] port Ethernet 1/0/1 to Ethernet 1/0/3

[SwitchB-vlan100] igmp-snooping enable

[SwitchB-vlan100] quit

# Enable dropping unknown multicast packets.

[SwitchB] unknown-multicast drop enable

Configuring Switch C

# Enable IGMP Snooping globally.

<SwitchC system-view

[SwitchC] igmp-snooping enable

Enable IGMP-Snooping ok.

#Create VLAN 100, assign Ethernet 1/0/1 through Ethernet 1/0/3 to VLAN 100, and enable IGMP Snooping in this VLAN.

[SwitchC] vlan 100

[SwitchC-vlan100] port Ethernet 1/0/1 to Ethernet 1/0/3

[SwitchC-vlan100] igmp-snooping enable

c CAUTION: As Switch C is not the IGMP Snooping querier, it cannot create forwarding entries for Host A and Host B, and therefore, do not enable the function of dropping unknown multicast packets on Switch C. To avoid impact on the network and on Switch C caused by multicast flooding, it is recommended to enable IGMP Snooping querier on the switch to which the multicast source is directly attached.