3Com Switch 7750 Configuration Guide

Displaying and Maintaining IGMP Snooping 437
■ If you configure IGMP Snooping simulated joining in Ethernet port view, the
Ethernet port must belong to the specified VLAN; otherwise the configuration
does not take effect.
■ You can use the source-ip source-address command to specify a multicast
source address that the port will join as a simulated host. This configuration
takes effect only when IMGPv3 Snooping is enabled in the VLAN.
Configuring Multicast
VLAN
In the current multicast mode, when users in different VLANs order the same
multicast packet, the multicast stream is copied to each of the VLANs. This mode
wastes a lot of bandwidth.
By configuring a multicast VLAN, adding switch ports to the multicast VLAN and
enabling IGMP Snooping, you can make users in different VLANs share the same
multicast VLAN. This saves bandwidth because multicast streams are transmitted
only within the multicast VLAN and also guarantees security because the multicast
VLAN is isolated from user VLANs completely. Therefore, multicast information
streams can be transmitted to users continuously if multicast VLAN is configured.
Perform the following configuration to configure multicast VLAN.
c
CAUTION:
■ You can configure up to 5 multicast VLANs for the device.
■ A multicast VLAN cannot be configured as a multicast sub-VLAN.
■ A multicast sub-VLAN cannot be configured as a multicast VLAN.
■ A multicast sub-VLAN cannot be configured as the sub-VLAN of another
multicast VLAN.
■ A multicast sub-VLAN is corresponding to a multicast VLAN only.
■ If multicast routing is enabled on a VLAN interface, the corresponding VLAN
cannot be configured as a multicast VLAN.
Displaying and
Maintaining IGMP
Snooping
After the configuration above, you can execute the display command to verify
the configuration by checking the displayed information.
You can execute the reset command to clear the statistics information about
IGMP Snooping.
Table 349 Configure multicast VLAN
Operation Command Description
Enter system view system-view -
Enable the IGMP snooping function
globally
igmp-snooping enable Required
Enter VLAN view vlan vlan-id -
Enable the IGMP snooping function igmp-snooping enable Required
Enable the multicast VLAN function multicast-vlan enable Required
Configure the mapping relationship
between multicast VLAN and multicast
sub-VLANs
multicast-vlan vlan-id subvlan
vlan-list
Required