Hub-spoke OCVPN with inter-overlay source NAT

This topic shows a sample configuration of hub-spoke OCVPN with inter-overlay source NAT. OCVPN isolates traffic between overlays by default. With NAT enabled on spokes and assign-ip enabled on hub, you can have inter-overlay communication.

Inter-overlay communication means devices from any source addresses and any source interfaces can communicate with any devices in overlays' subnets when the overlay option assign-ip is enabled.

You must first disable auto-discovery before you can enable NAT.


  • Free license: Hub-spoke network topology not supported.
  • Full License: Maximum of 2 hubs, 10 overlays, 64 subnets per overlay; 1024 spokes, 10 overlays, 16 subnets per overlay.


  • All FortiGates must be running FortiOS 6.2.0 or later.
  • All FortiGates must have Internet access.
  • All FortiGates must be registered on FortiCare using the same FortiCare account.


  • Non-root VDOMs do not support OCVPN.