Fortinet FortiGate 4000 User Guide

The VLAN ID of each VLAN subinterface must match the VLAN ID added by the IEEE 
802.1Q-compliant router. The VLAN ID can be any number between 1 and 4096. 
Each VLAN subinterface must also be configured with its own IP address and 
netmask.

You add VLAN subinterfaces to the physical interface that receives VLAN-tagged 
packets.

Go to System > Network > Interface.

Select Create New to add a VLAN subinterface.

Enter a Name to identify the VLAN subinterface.

Select the physical interface that receives the VLAN packets intended for this VLAN 
subinterface.

Enter the VLAN ID that matches the VLAN ID of the packets to be received by this 
VLAN subinterface.

Select the virtual domain to which to add this VLAN subinterface.
See 

 for information about virtual domains.

Select the name of a zone if you want this VLAN subinterface to belong to a zone.
You can only select a zone that has been added to the virtual domain selected in the 
previous step. See 

 for information about zones.

Configure the VLAN subinterface settings as you would for any FortiGate interface.
See 

Select OK to save your changes.
The FortiGate unit adds the new VLAN subinterface to the interface that you selected 
in step

Note: A VLAN must not have the same name as a virtual domain or zone.