3Com Switch 8800 Advanced Software V5 Configuration Guide

Configuring Basic Functions of IGMP Snooping 545
n
■ IGMP Snooping must be enabled globally before it can be enabled in a VLAN.
■ When you enable IGMP Snooping in a specified VLAN, this function takes
effect for Ethernet ports in this VLAN only.
■ After enabling IGMP Snooping in a VLAN, you cannot enable IGMP and/or PIM
on the corresponding VLAN interface, and vice versa.
Configuring the Version
of IGMP Snooping
By configuring the IGMP Snooping version, you actually configure the version of
IGMP messages that IGMP Snooping can process.
■ IGMP Snooping version 2 can process IGMPv1 and IGMPv2 messages, but not
IGMPv3 messages, which will be flooded in the VLAN.
■ IGMP Snooping version 3 can process IGMPv1, IGMPv2 and IGMPv3 messages.
Follow these steps to configure the version of IGMP Snooping:
c
CAUTION: If you switch IGMP Snooping from version 3 to version 2, the system
will clear all IGMP Snooping forwarding entries from dynamic joins, and will:
■ Keep forwarding entries for version 3 static (*, G) joins;
■ Clear forwarding entries for version 3 static (S, G) joins, which will be restored
when IGMP Snooping is switched back to version 3.
For details about static joins, Refer to “Configuring Static Ports” on page 546.
Configuring the
Function of Dropping
Unknown Multicast
Data
Unknown multicast data refers to multicast data whose forwarding entries do not
exist in the corresponding multicast forwarding table:
■ With the function of dropping unknown multicast data enabled, the switch
drops all the unknown multicast data received.
■ With the function of dropping unknown multicast data disabled, the switch
floods unknown multicast data in the VLAN to which the unknown multicast
data belongs.
Follow these steps to configure the function of dropping unknown multicast data:
Enable IGMP Snooping
globally and enter IGMP
Snooping view
igmp-snooping Required
Disabled by default
Return to system view quit -
Enter VLAN view vlan vlan-id -
Enable IGMP Snooping in the
VLAN
igmp-snooping enable Required
Disabled by default
To do... Use the command... Remarks
To do... Use the command... Remarks
Enter system view system-view -
Enter VLAN view vlan vlan-id -
Configure the version of IGMP
Snooping
igmp-snooping version
version-number
Optional
Version 2 by default