Planet VC-820M User Manual page 87

4.4.5.2 Q-in-Q Tunnel Setting
Business customers of service providers often have specific requirements for VLAN IDs and the number of VLANs to be
supported. The VLAN ranges required by different customers in the same service-provider network might overlap, and
traffic of customers through the infrastructure might be mixed. Assigning a unique range of VLAN IDs to each customer
would restrict customer configurations and could easily exceed the VLAN limit (4096) of the IEEE 802.1Q specification.
Using the Q-in-Q feature, service providers can use a single VLAN to support customers who have multiple VLANs.
Customer VLAN IDs are preserved, and traffic from different customers is segregated within the service-provider network,
even when they appear to be in the same VLAN. Using Q-in-Q expands VLAN space by using a VLAN-in-VLAN hierarchy
and retagging the tagged packets. A port configured to support Q-in-Q is called a Q-in-Q user-port. A port configured to
support Q-in-Q Uplink is called a Q-in-Q uplink-port.

To configure Q-in-Q Port
1. To enable global Q-in-Q function, select Q-in-Q and enable "Enable".
2. Fill out Q-in-Q Tpid.
3. To enable port Q-in-Q function, select Q-in-Q checkbox for special port.
4. To enable port Q-in-Q Uplink function, select Q-in-Q Uplink checkbox for special port.
Figure 4-4-5-2: Q-in-Q Tunnel Setting interface
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User's Manual of VC-820M