GL.iNet's AdGuard Home Hides Upstream DNS Settings in a Non-Obvious Place
On a recent trip I kept getting connection failures that needed retrying — pages half-loading, API calls timing out, the usual DNS-smells-wrong experience. It was intermittent enough to be annoying but consistent enough that I knew something was actually broken.
I narrowed it down to DNS pretty quickly. My GL.iNet MT-3000 travel router was dropping queries or returning nothing for some domains.
The culprit turned out to be obvious in retrospect: before leaving I had shut down my Pi-hole servers at home. Those Pi-holes live on my Tailscale network, and my travel router connects back to that network. Somewhere, something was still trying to use them for DNS.