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Multicast VLAN configuration
This chapter includes these sections:
•
Introduction to multicast VLAN
•
Multicast VLAN configuration task list
•
•
Displaying and maintaining multicast VLAN
•
Multicast VLAN configuration examples
Introduction to multicast VLAN
In the traditional multicast programs-on-demand mode shown in
, 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 17 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.
As shown in
, Host A, Host B and Host C are in three different user VLANs. All user
ports—ports with attached hosts—on Switch A are hybrid ports. On Switch A, configure VLAN 10 as
a multicast VLAN, assign all user ports to this multicast VLAN, and enable IGMP snooping in the
multicast VLAN and all user VLANs.