The worst case scenario if your DNS is leaked is that your ISP will see your activity. Depending on your location it might not matter at all. However, if you are in the US, Germany or a country that has more strict laws regarding internet activity, DNS leak is something you might want to avoid.
To fix this problem instead of using DHCP settings try to use static DNS server or public DNS services
To change DNS settings open Control panel and go to Network and Sharing Center. Navigate to Change Adapter Settings on the left-hand panel and locate your network and Right click on the network icon. Select Properties from the drop-down menu.
Locate and search Internet Protocol Version 4 in the window and then click on it and then go to Properties.
Click on the radio button Use the following DNS server addresses.
Enter the Preferred and Alternate address for DNS servers you wish to use.
If you want to use Google Open DNS server, follow these steps
Locate preferred DNS server and type 188.8.131.52
Locate alternate DNS server and type 184.108.40.206.
Click on OK to save the changes.
Solution 2 (Disable Smart Multi-Homed Name Resolution.)
Windows 8 and 8.1
Create a file and name it dns.reg. Then place the following command in the file:
Windows Registry Editor Version 5.00
Press WIN+R and write gpedit.msc
Expand Administrative templates
Double-click "Turn off smart multi-homed name resolution"
Check the box called "Enabled"
Click "Apply all" and then "OK"
Finally, reboot your PC and you are done!
For Windows 10, the easy fix it to add a DWORD name of DisableSmartNameResolution with a value of 0 under the following path.