Random VPN Disconnections

Hi boyl99,

Understand the scope of the issue, i.e., whether all users or some users are having the SSL VPN disconnection issue.

See if any applications on the user's computer could conflict with FortiClient (for example, Cisco's AnyConnect).

FortiClient logs (under 'FCDiagData\general\logs\trace\sslvpndaemon_1_error.log') showing errors such as 'WSAEnumNetworkEvents FD_CLOSE (10053)' normally indicate there are conflicting applications on the computer.

Authentication Timeout and idle timeout settings could also be checked on the FortiGate. By default, an SSL VPN connection logs out after 8 hours due to the auth-timeout.

config vpn ssl setting
set idle-timeout 300

set auth-timeout 28800
end

The idle-timeout is the time in seconds that the SSL VPN will wait before timing out.
The default value is 300 seconds (5 minutes). Range: <0> to <259200>.
The auth-timeout is the time in seconds that the SSL VPN will wait before re-authentication is enforced.
The default value is 28800 seconds (8 hours). Range: <0> to <259200>.

Please refer to the document below, which describes random or intermittent disconnections of the SSL VPN tunnel to the FortiGate when connected with FortiClient:

https://community.fortinet.com/t5/FortiGate/Technical-Tip-SSL-VPN-disconnection-issues-when-connected-with/ta-p/207851

Additionally, refer to the document below that describes common causes of IPSec VPN disconnection issues and provides a systematic approach to troubleshooting intermittent disconnections in FortiGate IPSec VPN deployments:

https://community.fortinet.com/t5/FortiGate/Technical-Tip-Understanding-and-troubleshooting-IPSec-VPN/ta-p/397214

If you have found a solution, please like and accept it to make it easily accessible to others.

Regards,
Aman