If you’re using an OpenVPN client on Windows 10 and you use the block-outside-dns option to prevent DNS leaks then you may experience some serious connection delays.
The easiest way to fix the block-outside-dns connection issue is through the Network and Sharing Center, here’s how to do it:
Step 1 – Right click network in system tray and select Open Network and Sharing Center
Step 2 – Right click the TAP-Windows Adapter and select properties
Step 3 – Select TCP/IPv4 or TCP/IPv6 depending on which you use and click Properties
Step 4 – Click on advanced tab, uncheck Automatic and set Interface metric to 1
Once you’ve done this click on ok, disconnect from your VPN or SVPN and reconnect to it and your block-outside-dns problem should be fixed.
The lower the Interface metric number the higher its network adapter’s priority and if you have quite a few network adapters the problem can get quite bad.
I hope this helps!