Test Your Google DNS Block
To test if you successfully blocked Google DNS servers, you can perform a ping test to see if it's working.
To run a ping test you open Command Prompt (Windows) or Terminal (Mac) and enter the following command:
"ping 18.104.22.168" and "ping 22.214.171.124"
If you successfully blocked Google's DNS servers you should get an error saying that the request timed out, or that the destination host was unreachable.