There are two configuration modes available on the FortiGate for FortiExtender integration: WAN extension mode and LAN extension mode.
In WAN extension mode, the FortiExtender works as an extended WAN interface in IP pass-through mode. The FortiGate manages FortiExtender over the CAPWAP protocol in IP pass-through mode, and is integrated into FortiOS as a manageable interface.
Sample configurations in WAN extension mode could include connecting a FortiExtender to two FortiGates in HA active-passive mode, or connecting two FortiExtenders to two FortiGates in HA active-active mode to provide dual active redundancy for wireless WAN access.
For more information, see FortiExtender and FortiGate integration in the FortiExtender (Managed) Administration Guide.
The LAN extension configuration mode allows FortiExtender to provide remote thin edge connectivity back to the FortiGate over a backhaul connection. A FortiExtender deployed at a remote location will discover the FortiGate access controller (AC) and form an IPsec tunnel (or multiple tunnels when multiple links exist on the FortiExtender) back to the FortiGate. A VXLAN is established over the IPsec tunnels to create an L2 network between the FortiGate and the network behind the remote FortiExtender.
For more information, see FortiExtender as FortiGate LAN extension in the FortiExtender (Managed) Administration Guide.