Troubleshooting Tip: Basic Example of VLAN stacking (QinQ) Configuration

[riteshpv]

Description	This article provides a simple example of a basic VLAN stacking (QinQ) configuration terminating on a FortiSwitch.
Scope	FortiSwitch v7.4, v7.6.
Solution	The ISP, connected to port1 of the FortiSwitch, forwards S-VLAN 2540 and C-VLAN 1501. A server is connected to port49 and sends traffic tagged with VLAN 1501. The requirement is to tunnel VLAN 1501 inside VLAN 2540 for traffic sent towards the ISP. Configuration on FortiSwitch: config switch interface     edit "port1"         set description "ISP-port"         set allowed-vlans 2540     next         edit "port49"             set description "server-port"       <----- Configure Q-in-Q on the server-facing port.             set native-vlan 2540                 config qnq                     set status enable                         config vlan-mapping                             edit 1                                 set match-c-vlan 1501                                     set new-s-vlan 2540                                 next                             end                         end                     next                 end Explanation: port1 (uplink to ISP): Accepts traffic on VLAN 2540. port49 (server-facing): Configured with Q-in-Q enabled to encapsulate customer VLAN 1501 traffic inside service VLAN 2540. This configuration ensures that traffic from the server, tagged with VLAN 1501, is encapsulated within VLAN 2540 before being forwarded to the ISP. Important Note: Not all FortiSwitches support QinQ. Refer to: Feature-matrix, search 'VLAN stacking (QinQ)'.