Since the Chromecast has Google’s DNS servers hardcoded, you will need a router with custom firmware like Tomato or DD-WRT to get Netflix region switching on the Chromecast working.

Setting up your router is outside the scope of this guide. You can however find useful information here and here.

It should be noted that there is an alternative method not requiring a router with custom firmware: All you have to do is block 8.8.8.8 and 8.8.4.4 at the router level. If your router is capable of blocking access to specific IP addresses, you don’t need a router with custom firmware. Setting this up is however outside of the scope of this guide. We have created guides on how to block Google DNS in your router here, for routers not listed there, Google is your friend