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10.1.5 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 problem above can be solved by configuring a multicast VLAN. By adding 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.
Choose the menu Multicast→IGMP Snooping→Multicast VLAN to load the following page.
Figure 10-9 Multicast VLAN
The following entries are displayed on this screen:
Multicast VLAN
Multicast VLAN: Enable/Disable Multicast VLAN feature.
VLAN ID: Enter the VLAN ID of the multicast VLAN.
Router Port Time:
Specify the aging time of the router port. Within this time, if the
switch doesn’
t receive IGMP query message from the router port,
it will consider this port is not a router port any more.
Member Port Time:
Specify the aging time of the member port. Within this time, if the
switch doesn’
t receive IGMP report message from the member
port, it will consider this port is not a member port any more.
Leave Time:
Specify the interval between the switch receiving a leave message
from a host, and the switch removing the host from the multicast
groups.
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