H3C Technologies H3C S7500E Series Switches - Manual (Page 72)

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Multicast VLAN Configuration
When configuring multicast VLAN, go to these sections for information you are interested in:
z Introduction to Multicast VLAN
z Multicast VLAN Configuration Task List
z Configuring Sub-VLAN-Based Multicast VLAN
z Configuring Port-Based Multicast VLAN
z Displaying and Maintaining Multicast VLAN
z Multicast VLAN Configuration Examples
Introduction to Multicast VLAN
As shown in Figure 3-1 , in the traditional multicast programs-on-demand mode, when hosts,
Host A, Host B and Host C, belonging to different VLANs require multicast programs on
demand service, the Layer 3 device, Router A, needs to forward a separate copy of the
multicast traffic in each user VLAN to the Layer 2 device, Switch A. This results in not only
waste of network bandwidth but also extra burden on the Layer 3 device.
Figure 3-1 Multicast transmission without multicast VLAN
The multicast VLAN feature configured on the Layer 2 device is the solution to this issue. With
the multicast VLAN feature, the Layer 3 device needs to replicate the multicast traffic only in the
multicast VLAN instead of making a separate copy of the multicast traffic in each user VLAN.
This saves the network bandwidth and lessens the burden of the Layer 3 device.
The multicast VLAN feature can be implemented in two approaches, as described below:
Sub-VLAN-based multicast VLAN
As shown in Figure 3-2 , Host A, Host B and Host C are in three different user VLANs. On
Switch A, configure VLAN 10 as a multicast VLAN, configure all the user VLANs as sub-VLANs
of this multicast VLAN, and enable IGMP Snooping in the multicast VLAN.