Random FortiClient (IPsec VPN) disconnects
Some of our user's FortiClient IPsec VPN connection (Windows 10 x64, FortiClient 6.0.9, FortiGate 6.0.9) drops numerous times a day. Some users have to reconnect more than 10 times a day. The connection simply drops while they are working, and for no apparent reason as applications such as Skype, Teams etc. remain online. Even if there was packet loss for a moment, it must have been very brief.
This does not affect all of of our users. For the majority of our users the FortiClient connection is pretty stable. In my experience, the quality of the Internet link makes a big difference. I have experienced frequent disconnects myself on my ADSL home Internet link whereas I don't experience any disconnects anymore now that I am on fibre. All workstations are set up using an image and are therefore identical in the way they are configured. So I don't think the problem lies there.
All users connect to the same IPsec dialup tunnel (ike=1, authentication=psk, mode=aggressive, lifetime=86400/43200, dpd-retrycount=3, dpd-retryinterval=15) and since this is not affecting everyone, I guess we can rule out an issue on the FortiGate too. This therefore points to the FortiClient itself.
Is anyone else experiencing this? Are there any recommendations to make the FortiClient more resilient in this regard? This issue has been bugging us for almost three years. We have started with FortiGate/FortiClient 5.4.x and upgrading to different versions (which is something Support always likes to suggest) has made zero difference. I have opened another ticket with Support a few weeks ago but there has not been any progress so far.
I would appreciate your input on this. Thank you.