1-1
1
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 1-1
, 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 1-1
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 1-2
, 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.
