Disconnects with Windows 11 PC / 5G Router

[r4ndom81]

Hi,
i'm using Forticlient VPN  now since approx 1.5 years for work, without any problems.
Usually i connect over a DSL Line with a LAN-Cable connected to my Windows 10 PC.
Sometimes, due to provider problems, i also use a Mobile Data Card, which is operating in a 5G Router. It provides a Wifi net, which my W10 PC connects to and Forticlient also runs smoothly.

Recently, i got a second machine with Windows 11 installed. Over the "normal" house-Wifi everything also works but when i try to use the same 5G Router connection, which is still working on my Windows 10 machine, Forticlient connects and then always immediately disconnects. Tried also to connect the 5G Router with a cable, but same effect...

Maybe someone knows this kind of preoblems and may help. Would appreciate :)

Cheers

[ezhupa]

Hello r4ndom81, 

Have you run any ike debug on the FortiGate when trying to connect via FortiClient? 
The commands would be as follows:
diagnose vpn ike log-filter dst-addr4 <Remote-GW> (your public IP address)
diagnose debug application ike -1
diagnose debug console timestamp enable
diagnose debug enable

May be useful:

Starting from FortiOS 7.4.1, the 'diagnose vpn ike log-filter dst-addr4' command has been changed to 'diagnose vpn ike log filter rem-addr4'.

Also I found this old post in the forum regarding issues with FCT and Windows11 but in this case it was not related only to a Mobile Data Card.  Maybe it helps:
https://community.fortinet.com/t5/Support-Forum/Client-VPN-IPSEC-with-FortiClient-fail/m-p/281436#M2...

Best Regards,
Enea

[r4ndom81]

Hi, and thanks for the reply!

Could you elobarte some more - i sadly dont have any experience in running debug logs. Im just a (very) simple user which hasnt any clue about the deeper possibilities of the programm, forgive me.

Cheers

[ezhupa]

Hello,

Those commands would need to be run on the FortiGate where you are connecting if you are using an IPSEC VPN. In case of SSL VPN you would need to run other commands. Are you the FortiGate administrator and have access to the device??

[r4ndom81]

Hi,
Afaik i use an SSL VPN Connection over Forticlient, but i dont know about any FortiGate nor im an admin.....as said im just a normal windows enduser which uses just the programm to work remotly :)

[r4ndom81]

....and for the link you provided: As i understood, a driver downgrade is recommended. Ive an Intel ethernet adapter in my machine, dont know if the Realtek driver is suitable. Got to the point right before installing, but windows gave me a warning on this procedure and dont wanna break things at this point.

[AEK]

Hi @r4ndom81 

In case you are using SSL VPN, can you try disable IPv6 on your Windows 11 before connecting to VPN?

[r4ndom81]

Hi,
thanks. I think i ve disabled IPv6 (am not sure if this was right, cause im not into network settings, just a normal windows user), but forticlient didnt connect after that.

In general, the problems are still present with unaltered windows settings. Forticlient connects, i see a short upload and then disconnects...

Cheers

[r4ndom81]

...ok, i tried again and properly disabled IPv6 now: Same behavior though. Fortinet Cleint didnt connect at all and gives me an error message :" VPN connect failed.Please check your configuration and network connection...."

So it seems, this doesnt work sadly.

[robR]

Hi Mate, Have you had any luck?  Look like I have same issue.  Worked fine for years, just stopped no reason.  I have pulled everything apart and rebuilt with no luck, and my IT have walked away (du'h!).

I think it may be in the router, but that is so specific no-one can help.

Doesnt help that I am not an IT person, just an end user!