R3102-R3103-HP 6600/HSR6600 Routers IP Multicast Configuration Guide

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Configuring multicast VLANs
Overview
Figure 109 shows the traditional multicast programs-on-demand mode. When the hosts ( Host A, Host B,
and Host C) that belong to different VLANs require the multicast programs-on-demand service, the Layer
3 device (Switch A) must forward a separate copy of the multicast data in each VLAN to the Layer 2
device (Switch B). This causes a waste of network bandwidth and adds an extra burden on the Layer 3
device.
Figure 109 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 the Layer 2 device, the Layer 3 device only replicates the multicast data in the multicast
VLAN instead of making a separate copy in each VLAN. This saves network bandwidth and lessens the
burden on the Layer 3 device.
This feature is available only when the SAP module is operating in bridge mode.
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 Figure 110, Host A, Host B, and Host C are in VLAN 2 through VLAN 4, respectively. On
Switch B, VLAN 10 is configured as a multicast VLAN, VLAN 2 through VLAN 4 are configured as
sub-VLANs of VLAN 10, and 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 B
Receiver
Host B
Receiver
Host C
Switch A
IGMP querier