Because Circle utilizes ARP Spoofing to manage devices, the DNS settings on your device may fall back to the router settings.
Not sure what DNS is? Read more below!
What is DNS?
DNS, or the Domain Name System, is like a routing list for the Internet similar to how a phone call works. When you make a phone call, you enter a sequence of numbers to connect to the right line. A contact list routes that number to a particular person or home in order to connect the call.
The Domain Name System does the same thing for websites and servers. While you enter Google.com to open your search engine, your browser and computer connect to a server identified by an IP address (a series of numbers separated by periods) to load that site. The Domain Name System connects a domain like Google.com to an IP address. Some techy folks out there like to set up custom DNS settings on a device for different reasons. For example they might be using a parental control service to manage their DNS settings and what the device can and cannot connect to. You might even say that Circle Home is like custom DNS settings that you set up differently for your devices depending on their Profile and Filter Level.
If you're using custom DNS settings on a device, you probably know about them already. Importantly, those DNS settings won't work consistently if the device is managed by Circle.
Why can't I use custom DNS settings on my device?
When you manage a device using Circle (set it to a profile with a Filter Level of Adult or lower), the device's outbound Internet traffic will be intercepted using ARP spoofing. If the traffic is allowed to go through based on your Filter Level settings, its DNS will fallback to the router's settings and not the device's.
Unfortunately, there isn't a way to prevent this other than setting the device to "Unmanaged" or putting the profile on a Filter Level of None. You'll need to make the choice between those custom DNS settings different than your router versus managing a device using Circle.