Well as long as the TLD isn’t used by anyone it should work internally regardless of what ICANN says, especially if I add it to etc/hosts
Sure, you can do whatever you want. You could even use non-rfc1918 addresses and nobody can stop you. It’s just not always a great idea for your own network’s functionality and security. You can use an unregistered TLD if you want, but it’s worth knowing that when people and companies did that in the past, and the TLD was later registered, things didn’t turn out well for them. You wouldn’t expect .foo to be a TLD, right? And it wasn’t, until it was.
German router and network products company AVM learned the hard way that this is a bad idea. They use fritz.box for their router interface page and it was great until tld .box became publicly available and somebody registered fritz.box.
Having a reserved local/internal only tld is really great to prevent such issues.
I agree that this is a good idea, but I wanted to add that if someone owns a domain already, they can also use that internally without issue.
If you own a domain and use Let’s Encrypt for a star cert, you can have nice, well secured internal applications on your network with trusted certificates.
You don’t even need a star cert… The DNS challenge works for that use case as well.
That is great when using only RFC 1918 IPv4 addresses in the network, but as soon as IPv6 is added to the mix all those internal only network resources can becomes easy publicly available and announced. Yes, this can be prevented with firewalling but it should be considered.
