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My local network does not work since VPN install


I have a local network and one of those machines has the Cisco VPN client installed. Now VNC fails to connect to that machine with the VPN client, even if the VPN client is not running. I also notice trouble using ftp to outside sites, again, without being on the VPN.
It seems as if I was behind some firewall but I cannot find any. I turned off the Windows Firewall completely already.


The reason is a certain driver that Cisco's VPN client installed on your machine. It is called 'Deterministic Network Enhancer'. This driver is active even if you do not load the VPN client.
You can see it in the control panel, click on 'network connections' and there right-click on your ethernet card.
You could in theory disable or remove this enhancer there and you would instantly be able to VNC into your machine again, however, this requires a reboot and afterwards your VPN won't work anymore.

Luckily there is a solution around.
  1. Start the VPN client
  2. In the tray, right-click on the icon
  3. Uncheck "Stateful Firewall (Always On)
VPN and VNC at the same time
Now your local network will work again. You could even make this change temporarily, e.g. remove the check, VNC into the machine, then add the check again, while your VNC connection remains alive.

Generated 12:01:49 on Sep 19, 2020