IP-Sec VPN not working (solved)

[Thomas_Roes]

I solved an issue where I was unable to make an IP-Sec connection with my laptop, while others were succesfull.

I mention it here, for I solved it, but did not find this solution here.

Quick one:

Look for other VPN software that capture your local UDP 500 / 4500 ports. Fritz!VPN

Troubleshooting log:

First discovery: Wireshark does not see any outbound traffic to the VPN gateway.

Second discovery: in C:\Program Files\Fortinet\FortiClient\logs\trace\FortiVPN_1_error.log:

repeated

[2025-09-17 10:03:32.9410049 UTC+02:00] [3032:94940] [FortiVPN 1236 error] fortivpn::IFortiVPN_Impl::LowPowerWakeUp() NOT PBT_POWERSETTINGCHANGE
[2025-09-17 10:03:32.9428086 UTC+02:00] [3032:94940] [FortiVPN 1261 error] fortivpn::IFortiVPN_Impl::LowPowerSleep() NOT PBT_POWERSETTINGCHANGE

Then I remembered, that IP-Sec (normally/alway's) has a fixed client port. So this should be available.

In CMD:

netstat -aon | find ":500"
TCP 10.10.2.1:50003 52.209.151.231:443 ESTABLISHED 9172
UDP 0.0.0.0:50073 *:* 11628
UDP [::]:500 *:* 27676

Looking up PID 27676 (This number will be different for you / evey time), I discovered it was bound to another VPN client (Fritz!VPN). I uninstalled this, and then it was bound to svchost.exe.

Now the VPN connects. While VPN is connected, port 500 is bound to ipsec.exe in the Forti Client.

Hope this helps someone.

Thomas Roes

[Debbie_FTNT]

Thanks for sharing the insight, Thomas!