Configuring OpenVPN Adapters

Much to my dismay this morning, I had problems opening a VPN connection home: The connection opened, but wouldn’t retrieve an IP address from the DHCP server… okay, not a problem, I can just manually set an IP and be on my merry way. It would have been that easy if the OpenVPN TAP adapter was displayed in the Network Connections Control Panel.

After some digging, it seems the easiest solution, is to remove the virtual adapter, re-configure the .inf file, then re-add the adapter. So let’s get started:

1. Delete existing virtual adapters:
   1. You have two options here:
      Start → All Programs → OpenVPN → Delete ALL TAP-Win32 virtual ethernet adapters
      or

      "C:Program FilesOpenVPNbintapinstall.exe" remove tap0801

2. Configure the TAP .inf file
   1. Navigate to “C:Program FilesOpenVPNdriver”
   2. Open OemWin2k.inf (name may vary) with your favorite text editor.
   3. Perform a search for “Characteristics = 0×89″. This brings me down to the [tap0801.ndi] section at line 86. It turns out that 0×89 is the configuration value for a hidden TAP adapter. We want the adapter to be visible in Network Connections so we can can easily configure it. To do that…
   4. Change 0×89 to 0×81 (The lines should now read: “Characteristics = 0×81″)
   5. Save and close the file
3. Add a new virtual adapter
   1. Again, you have two options…
      Start → All Programs →OpenVPN → Add a new TAP-Win32 virtual ethernet adapter
      or

      "C:\Program Files\OpenVPN\bin\tapinstall.exe" install "C:\Program Files\OpenVPN\driver\OemWin2k.inf" tap0801

You should now have a new Local Area Connection adapter in Network Connections. My recommendation is that you change this to something easily recognizable like, “OpenVPN Adapter”. Go ahead and open it up and configure as needed.