Getting Android and iOS to prioritize DNS 1 before trying DNS 2 on local network

Hello!

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I have a home server with an SSL cert. I have a few web applications that I leave publicly accessible but a good amount are internal only. As such, I set up a DNS server on my router to handle local connections for my server.

So going to example.com is given my public IP over the internet but at home it translates to my private IP.

For DNS advertising, my router has its own IP as DNS 1 and a public one for DNS 2.

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This solution seems to be working just find on my computers. My Android and iPad are not using DNS 1 most of the time and seems to flip flop. Sometimes, when I load the internal web app it works fine, but even on reloads it can fail because it used DNS 2. Even when manually specifying in the settings, it doesn't necessarily try DNS 1 before attempting DNS 2.

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I also have a VPN set up. When I VPN into my network, the internal pages load properly 100% of the time.

How could I force my mobile devices to try a specific DNS first while it is on the local network?

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