FortiClient IPSec not connecting in WiFi (no problem when wired)

[timbauer132]

Hi everyone,

Maybe someone has an idea on the following issue:

In our company, we use FortiClient IPSec. It always worked fine until I recently got a new Win 11 Notebook. The VPN still works fine as long as I use a wired connection. But I can't connect to our VPN anymore when using WiFi. It doesn't matter if I am at home or at a public place (or even when I am in the company WiFi -> obviously I would't need the VPN there, but the issue is the same). At all these places, FortiClient VPN has worked fine for a long time and it still works fine on several other company notebooks. So the problem has nothing to do with the WiFi networks or the Firewalls. The problem must have something to do with my notebook. I already reinstalled Windows. I deleted the driver for the Qualcomm FastConnect 6900 WiFi Network Adapter and reinstalled it. But the problems remains.

I kindly ask for your help!

Thanks a lot in advance

Tim

[xshkurti]

Hello Tim,

Can you try to disable IPv6 at WIFI Adapter when you connect to a network?

[timbauer132]

Hi xshkurti,

already did that - problem remains.

Yesterday I found an old driver for my network adapter. Using this driver, it connects most of the time, but the connection is very slow sometimes. Not an optimal solution.

[btan]

Hi timbauer132,

You may check out this post: https://community.fortinet.com/t5/Fortinet-Forum/Can-t-connect-to-IPsec-VPN-in-Windows-11/td-p/20222...

They had similar issue but it is working on Wifi but not Ethernet. 
Kindly check if you have similar the network adapter and follow the marked solution.

[timbauer132]

Hi btan,

as stated above, a driver downgrad is exactly what I did the day before yesterday and it really improved the situation. Using this driver, it connects most of the time, but the connection is very slow sometimes. Not an optimal solution.

[abarushka]

Hello Tim,

I would recommend to sniff affected traffic and check for anomalies. Moreover, I would recommend to check MTU.

[timbauer132]

Hi abarushka,

We couldnt find any anomalies.
MTU is 1500 for all adapters.

[abarushka]

Hello Tim,

I would recommend to sniff IKE and ESP traffic on FortiGate and PC simultaneously and check whether there is are packet drops.

Also I would recommend to load pcap sniffed on PC into wireshark and check (wireshark -> Analyze -> Expert information) for anomalies.

Moreover, you may consider to configure SSL VPN on FortiGate/FortiClient and IPsec tunnel for Windows native IPsec client for testing purposes.

[Phil1]

I've had the same problem for several months. Lenovo Z16, Qualcomm wi-fi driver, Windows 11. FortiClient won't connect over wi-fi but will connect over ethernet.
My client tried to raise a support ticket but was told Qualcomm not supported.
My work around: Disable the Qualcomm wi-fi adaptor. Purchase a TP-Link AC600 Nano Wi-fi usb adaptor (which installs a Realtek driver). I can now connect :)
Crazy that Microsoft/Qualcomm/FortiClient cannot resolve this issue.

[jeffreyyu]

Hi all. Has anyone found a solution to this issue? I have a client facing exactly the same. HP Pro X360 435 g9 laptop with Qualcomm FastConnect 6900 network adapter. Same thing happens, when connected via ethernet, it works but not through wifi.