192-168-1-1.backname.io works for me. It might be useful to get DV certs for temporary things that need HTTPS.

I've done a sorta similar thing to enable HTTPS for local network IPs for IoT: https://news.ycombinator.com/item?id=36593547

I didn't understand first either. I first discovered these playing around with Rancher which would use xip.io for the same thing.

The point is some protocols require you to actually resolve a domain name. For example, if you set up a vhost or reverse proxy with Apache or nginx, it will use the domain name to figure out what vhost you were trying to access. When you request a page like google.com the browser resolves that to an IP address, but it sends google.com with the request.

So say you have a reverse proxy at 1.2.3.4. You could make two vhosts: site1.1.2.3.4.backname.io and site2.1.2.3.4.backname.io and it would just work from any browser on your network.

You can do this locally using the hosts file before you set up your DNS for real, but a service like this means you don't even have to do that. Useful for quick experiments.

Ok, but piHole can also be used to set up fake domains to be used inside the network.

Think your company network where you can set up tests and stuff for colleagues but you don't control the DNS.

I guess it's the kind of thing if you need it, you'll know. There's no point looking for a reason to use this.

Something I encountered recently: I have a jellyfin server hosting shows and movies that I would like to play on my Chromecast on my local network.

This is 100% not possible. The Chromecast always hits Google's DNS to resolve the media server's address. Which means you must host your media under a resolvable domain name, exposed to the internet.

This kind of thing (assuming it can resolve through Google DNS) would short-circuit that requirement. You could feed it a domain name that points back to a local address and not expose your server to the internet.

Of course there are other ways around the problem, but this would be far, far simpler. Honestly it seems like it'd be faster and simpler than setting up a subdomain and reverse proxy, which is what I did.

Chromecast hits 8.8.8.8 and 8.8.4.4 for DNS, so if you can configure your router to route port 53 on those addresses to your router's address, then it will use your router's DNS server, which can resolve IP addresses on your local network.

Thanks, but I can do the same using PiHole and setting up a fake DNS

Some of the utility is that if you're on an IPv6-only connection that uses 464XLAT and are trying to connect to a host, DNS lookups are required for the 4-to-6 translation process.

There is always use cases for things.

I had to make something similar in the past just for my own use case.

The trick here is that this can be a value (rrdata) for NS records ;)

Or CNAME rrdata. Or MX rrdata. Albeit, there is little point in using it this way, as oppose to just add A record in your own domain anyway...

For people without a domain and a static IP, this may be useful too too publish a page, and possibly obtaining ACME tls cert.