Consider the following scenario:

- You configure your home computer to accept incoming VPN connections, allowing access to your home LAN.
- You configure your work computer to accept incoming VPN connections, allowing access to your work LAN.
- You create the appropriate network connections on each computer to be able to successfully connect to the other, in the same way as you were previously successfully able to do in previous versions of Windows.
- Either or both of the computers are running Windows 8/8.1 .

In this scenario, a VPN connection you establish from one computer to the other (in either direction) will appear to be unstable and/or seemingly randomly disconnect.

One possible reason -- notably, the one that has been causing many of my clients who are using Windows 8/8.1 headaches -- is far from obvious, but is documented in the following Knowledge Base article:

KB2919900 - Windows Connection Manager disconnects WLAN if a VPN connection is established

If you follow the instructions in the Resolution section of the article, VPN connections under Windows 8/8.1 will function substantially in line with how they do in all previous versions of Windows. Note: To open the Local Group Policy Editor, run gpedit.msc .

Also, if you are connecting to a 3rd-party VPN server, have a look at the following Knowledge Base article:

KB2955808 - A VPN connection through a third-party VPN server disconnects after an hour on a computer that is running Windows 8.1 or Windows 8