I recently picked up a Chromecast and am having some issues with it. I use a 3rd part DNS service to access Netflix content from other regions, but the Chromecast is programmed to specifically use Google's DNS servers regardless. I've been told the only way of dealing with this short of rooting the Chromecast and messing around with mods, is to block access to Google's DNS servers (18.104.22.168, 22.214.171.124) so they will time out when the Chromecast tries to access them, and "fall back" on the regular DNS settings.
The two main solutions I've seen involve either setting up Static Routing or configuring the router's firewall to block access to those IP addresses, but I can't figure out where to do this on the DPC3825. The IP address filtering seems to only apply to blocking internal IP addresses from accessing the internet at all, which I don't want. Any suggestions?