This tutorial is about blocking ALL traffic outside of the VPN connection which reveal your real IP address and also work as DNS Leak Fix. This works ONLY for Viscosity users and ONLY if you have ANY firewall (in my case I'm using GData Internet Security 2015). Why only for Viscosity? Because Viscosity makes it very easy for us by creating network adapters and I had trouble applying the Comodo guide to GData Firewall.
In short: We simply block ALL traffic on our others network adapters and just allow Viscosity (and the network adapters of viscosity).
Step by step:
1. Create a new rule set called AirVPN or whatever else.
2. We need a to create only a few custom rules in our rule set
3. We need to allow the Openvpn.exe inside of the Viscosity folder. I recommend using the assistant of GData.
3a) We need to allow in/out connections to our homework by allowing connections from 192.168.0.0 to 192.168.255.255
3b) We need to allow in/out connections to AirVPN in general, because GData has no kind of collection we must create for every IP a rule. We allow in/out connections to 220.127.116.11 and to 18.104.22.168
3c) Next we allow connections to the AIRVPN server(s) in this case I'm allowing connections to the AirVPN Switzerland server //Edit: This doesn't seem to be necessary at all.
3d) At the end we block ALL other traffic
4. As previously told Viscosity creates network adapters. So we just need to apply this rule set to our local network adapter only.
As soon as Viscosity has lost the connection, we are no longer be able to connect to the internet because our local network has been blocked.
But we can reconnect with Viscosity to our AirVPN servers. So we made sure that all traffic is going through our VPN tunnel.
This works with all firewalls that support these steps and its very easy to set up. Feedback is appreciated.