[unionpivo]

Most black boxes are just default linux distro with their vendor software on top.

Before systemd, you just needed to set correct DHCP config and it would all just work.

But nowdays distros come with systemd-resolved which usualy has (by deafult) fallback public DNS servers.

That means that boxes suddenly can switch from your DHCP network provided DNS servers (or even static DNS servers) to goolge (or cloudflare,) public DNS server.

Bottom line is, it used to be enough to set DNS server through DHCP (or static ones) that is no longer enough in some situations.

[eptcyka]

I'm not entirely certain that it is systemd-resolved's fault that the distro maintainers are setting default servers in the config. I'm not disputing that RHEL might, but debian certainly does not, nor any of the distros I've used recently, but I probably have a completely different perspective as I have to deal with more end-user focused distros. I do feel your pain though, DNS config management seems to be incredibly hard. And this fuckery where a OS default setting overrides the DHCP config you're pushing would be incredibly painful.