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Configuring multicast VLANs
This chapter describes multicast VLAN, how to configure multicast VLAN, and configuration
examples.
Overview
As shown in
, Host A, Host B, and Host C reside in different VLANs and require the same
multicast programs-on-demand service. Router A (Layer 3 device) must forward a separate copy of
the multicast data to Switch A (Layer 2 device). This occupies large bandwidth and increases the
burden on the Layer 3 device.
Figure 21 Multicast transmission without the multicast VLAN feature
The multicast VLAN feature on the Layer 2 device is the solution to this issue. After the multicast
VLAN is configured on Switch A, Router A sends only one copy of the multicast data to the multicast
VLAN on Switch A. This saves network bandwidth and lessens the burden on the Layer 3 device.
The multicast VLAN feature can be implemented in a sub-VLAN-based multicast VLAN and a
port-based multicast VLAN.
Sub-VLAN-based multicast VLAN
As shown in
:
•
Host A, Host B, and Host C are in VLAN 2 through VLAN 4, respectively.
•
On Switch A, VLAN 10 is a multicast VLAN.
VLAN 2 through VLAN 4 are sub-VLANs of VLAN 10.
IGMP snooping is enabled for the multicast VLAN.
Source
Receiver
Host A
Multicast packets
VLAN 2
VLAN 3
VLAN 4
VLAN 2
VLAN 3
VLAN 4
Switch A
Receiver
Host B
Receiver
Host C
Router A
IGMP querier