Run your favorite browser, like Google Chrome, or Microsoft Edge. Check your default gateway IP address. It is the IP address of the Xfinity modem/router. By default, the IP of the modem is 10.1.10.1. At the address bar, type in http://10.1.10.1. The default userid/password is cusadmin/highspeed. Look at the screenshot below.
Next, the same screen, go to Gateway –> Connection –> Local IP configuration. Check the checkbox “Assign DNS manually”. Change the two IP addresses, primary and secondary DNS to OPENDNS , 188.8.131.52 and 184.108.40.206 like the picture below:
Save the setting. That’s all. As the result, any device in your network using DHCP, it will pick up that two IP address for the DNS entries. To test if it works. Browse http://www.playboy.com, and if the browser response with this content, then it works.
For more information about OPENDNS visit their site. www.opendns.com