FortiGate Unable to establish the VPN connection. The VPN server may be unreachable.

Log on to the FortiGate unit via CLI and type below command to list top sessions.

diagnose sys top

Press Q to stop the listing.

Note the ipsengine process ID and execute below command to kill the process.

diagnose sys kill 11 <PID>

Now try to log in through FortiClient or by Web Browser.

If above steps doesn’t resolve the issue, follow below steps to restart the IPS Engine.

Execute below command to get IPS Engine test usage.

diagnose test application ipsmonitor

Above command will display all the test usage commands on IPS Engine.

Integer: Description
1: Display IPS engine information
2: Toggle IPS engine enable/disable status
3: Display restart log
4: Clear restart log
5: Toggle bypass status
6: Submit attack characteristics now
10: IPS queue length
11: Clear IPS queue length
12: IPS L7 socket statistics
13: IPS session list
14: IPS NTurbo statistics
15: IPSA statistics
97: Start all IPS engines
98: Stop all IPS engines
99: Restart all IPS engines and monitor

Now run the below command with test usage integer.

diagnose test application ipsmonitor <integer>

For example to restart all IPS engines and monitor run diagnose test application ipsmonitor 99