3Com 4200G 24-Port - Configuring a VLAN Tag for Query Messages; Configuring Multicast VLAN

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Configuring a VLAN Tag for Query Messages
By configuring the VLAN tag carried in IGMP general and group-specific queries forwarded and sent by
IGMP Snooping switches, you can enable multicast packet forwarding between different VLANs In a
Layer-2 multicast network environment.
Follow these steps to configure VLAN tag for query message:
Table 2-18 Configure VLAN Tag for query message
Operation Command Remarks
Enter system view
system-view
—
Enable IGMP Snooping
igmp-snooping enable
Required
By default, IGMP Snooping is
disabled.
Configure a VLAN tag for query
messages
igmp-snooping
vlan-mapping vlan vlan-id
Required
By default, no VLAN tag is
configured for general and
group-specific query messages
sent or forwarded by IGMP
Snooping.
It is not recommended to configure this function while the multicast VLAN function is in effect.
Configuring Multicast VLAN
In traditional multicast implementations, when users in different VLANs listen to the same multicast
group, the multicast data is copied on the multicast router for each VLAN that contains receivers. This is
a big waste of network bandwidth.
In an IGMP Snooping environment, by configuring a multicast VLAN and adding ports to the multicast
VLAN, you can allow users in different VLANs to share the same multicast VLAN. This saves bandwidth
because multicast streams are transmitted only within the multicast VLAN. In addition, because the
multicast VLAN is isolated from user VLANs, this method also enhances the information security.
Multicast VLAN is mainly used in Layer 2 switching, but you must make the corresponding
configurations on the Layer 3 switch.
Table 2-19 Configure multicast VLAN on the Layer 3 switch
Operation Command Remarks
Enter system view
system-view
—
Create a multicast VLAN and
enter VLAN view
vlan vlan-id
—
Return to system view
quit
—
Enter VLAN interface view
interface Vlan-interface
vlan-id
—