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.

License

• Free license: Hub-spoke network topology not supported.
• Full License: Maximum of 2 hubs, 10 overlays, 64 subnets per overlay; 512 spokes, 10 overlays, 16 subnets per overlay.

Prerequisites

• 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.

Restrictions

• Non-root VDOMs do not support OCVPN.
• FortiOS 6.2.x is not compatible with FortiOS 6.0.x.

OCVPN device roles

• Primary hub.
• Secondary hub.
• Spoke (OCVPN default role).

Sample topology

Sample configuration

You can only configure this feature using the CLI.

The overlay names on each device must be the same for local and remote selector pairs to be negotiated.

To enable inter-overlay source NAT in the CLI:

1. Configure the primary hub, enable overlay QA, and configure assign-ip and IP range:

   config vpn ocvpn
       set status enable
       set role primary-hub
       config overlays
           edit 1
               set name "QA"
               set assign-ip enable
               set ipv4-start-ip 172.16.101.100
               set ipv4-end-ip 172.16.101.200
               config subnets
                   edit 1
                       set subnet 172.16.101.0 255.255.255.0
                   next
               end
           next
           edit 2
               set name "PM"
               set assign-ip enable
               config subnets
                   edit 1
                       set subnet 172.16.102.0 255.255.255.0
                   next
               end
           next
       end
   end

2. Configure the secondary hub:

   config vpn ocvpn
       set status enable
       set role secondary-hub
   end

3. Configure spoke1 and enable NAT on the spoke:

   config vpn ocvpn
       set status enable
       set auto-discovery disable
       set nat enable
       config overlays
           edit 1
               set name "QA"
               config subnets
                   edit 1
                       set subnet 10.1.100.0 255.255.255.0
                   next
               end
           next
           edit 2
               set name "PM"
               config subnets
                   edit 1
                       set subnet 10.2.100.0 255.255.255.0
                   next
               end
           next
       end
   end

4. Configure spoke2 and enable NAT on the spoke:

   config vpn ocvpn
       set status enable
       set auto-discovery disable
       set nat enable
       config overlays
           edit 1
               set name "QA"
               config subnets
                   edit 1
                       set subnet 192.168.4.0 255.255.255.0
                   next
               end
           next
           edit 2
               set name "PM"
               config subnets
                   edit 1
                       set subnet 192.168.5.0 255.255.255.0
                   next
               end
           next
       end
   end
   

   A firewall policy with NAT is generated on the spoke:

   edit 9
      set name "_OCVPN2-1.1_nat"
      set uuid 3f7a84b8-3d36-51e9-ee97-8f418c91e666
      set srcintf "any"
      set dstintf "_OCVPN2-1.1"
      set srcaddr "all"
      set dstaddr "_OCVPN2-1.1_remote_networks"
      set action accept
      set schedule "always"
      set service "ALL"
      set comments "Generated by OCVPN Cloud Service."
      set nat enable
   next