PLANET FGSW-2840 - Manual (Page 146)

User’s Manual of FGSW-2840 / FGSW-4840S
4.6.1.4 Multicast VLAN
In old multicast transmission mode, when users in different VLANs apply for join the same multicast group, the multicast router
will duplicate this multicast information and deliver each VLAN owning a receiver one copy. This mode wastes a lot of
bandwidth.
The issue above can be solved by configuring a multicast VLAN. By adding Managed Switch ports to the multicast VLAN and
enabling IGMP Snooping, you can make users in different VLANs share the same multicast VLAN. This saves the bandwidth
since multicast streams are transmitted only within the multicast VLAN and also guarantees security because the multicast
VLAN is isolated from user VLANS.
Before configuring a multicast VLAN, you should firstly configure a VLAN as multicast VLAN and add the corresponding ports to
the VLAN on the 802.1Q VLAN page. If the multicast VLAN is enabled, the multicast configuration for other VLANs on the
VLAN Config page will be invalid, that is, the multicast streams will be transmitted only within the multicast VLAN. The screen in
Figure 4-6-9 appears.
Figure 4-6-9 : Multicast VLAN Page Screenshot
The page includes the following fields:
Object Description
Multicast VLAN
Select Enable/Disable Multicast VLAN feature.  Multicast VLAN
Enter the VLAN ID of the multicast VLAN.  VLAN ID
 Router Port Time Specify the aging time of the router port. Within this time, if the Managed Switch
doesn’t receive IGMP query message from the router port, it will consider this port
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