Forticlient VPN double NAT

[Fortilorz]

Hello Community,

i need help with double nat please. Fortigate 100F SSL VPN

Our Costumer cannot access our network through his Forti VPN client. The connection stops at 10%.

After investigations, the ISP informed us that they are using a double nat.

My question, what do I need to set on the Forticlient or Fortigate so that the VPN connection works.

I had never had such a case.
Thank you for your help

[Christian_89 · Accepted solution]

Change the FortiClient settings:
In the FortiClient, click the Settings tab.
Click the Advanced tab.
Select the Use NAT traversal check box.
Click Save to apply the changes.
Configure the Fortigate:
Open the Fortigate configuration from the CLI or the web interface.
Navigate to "VPN" > "SSL VPN Settings".
Activate "SSL VPN Tunnel Mode".
Click the "Advanced" button.
Select the "Use NAT traversal" checkbox.
Click "OK" to apply the changes.
Disable NAT on the Fortigate:
Open the Fortigate configuration from the CLI or the web interface.
Navigate to Network > Interfaces.
Select the interface on which the VPN connection is set up.
Click on the "Configuration" tab.
Uncheck the "Use NAT" option.
Click OK to apply the changes.

[Fortilorz]

Hello

Thank you for your message.

just a Question where do you mean in Forticlient by "Click the Advanced tab. Select the Use NAT traversal check box."

See the picture of Forti VPN Cleint below. I can't find the options

in Fortigate SSL VPN Tunnel Mode is already active.

but I can't find the other options---See the picture of Fortigate

regards

[Fortilorz]

Hello

we only have ssl vpn, do i need to set up ipsec vpn?

are these options only available in ipsec vpn?

but in Forticlient the options are also missing?

sorry for lot of questions

regards

[rohan02]

Hello,

Facing Forticlient VPN issues due to double NAT on Fortigate 100F SSL VPN? Resolve by configuring port forwarding on the ISP's router, enabling NAT traversal and UDP encapsulation on Fortigate, and considering SSL VPN usage. Ensure proper SSL VPN setup on both ends. Contact the ISP for specific recommendations on mitigating double NAT. Save changes, test the connection, and consult Fortigate support or community forums if problems persist.

You can also check this :

https://www.reddit.com/r/fortinet/comments/fx5zyf/ccsp coursedouble_nat_ipsec_site_to_site_and_ssl_vpn/ 

Best of luck!

I hope this will help you.