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Multicast VLAN configuration
Multicast VLAN overview
In the traditional multicast programs-on-demand mode shown in Figure 19, when hosts—Host A, Host B,
and Host C—that belong to different VLANs require multicast programs-on-demand service, the Layer 3
device—Router A—must 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 19 Multicast transmission without multicast VLAN
The multicast VLAN feature configured on the Layer 2 switch is the solution to this issue. With the
multicast VLAN feature, the Layer 3 device must 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 network
bandwidth and lessens the burden on the Layer 3 device.
The multicast VLAN feature can be implemented by the following approaches: sub-VLAN-based multicast
VLAN and port-based multicast VLAN.
Sub-VLAN-based multicast VLAN
As shown in Figure 20, Host A, Host B, and Host C are in different user VLANs. On Switch A, configure
VLAN 10 as a multicast VLAN, configure all user VLANs as sub-VLANs of VLAN 10, and enable IGMP
snooping in the multicast VLAN.
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