@See VPC, VPN, LAN, etc…

Corporate intranets (intranet essentially being “internal network” while internet is essentially “global network”) have existed for a long time but there are intranets all around us - everything on your side of your router can be treated as a local intranet and you can even set up a local DNS server (this is commonly used for ad blocking and I believe pi-holes use this technique though they might just use address blacklisting).

So, TL;DR you already do!