Comment on What path does data take when connecting to a domain at my address?
yaroto98@lemmy.world 1 day ago
Depends, you can set it up a few different ways.
you can set the dns so each subdomain resolves to a different port with your ip, in which case your router can forward that port to any local address on your network.
reverse proxy, this is most common. You use a service to do the translating for you. Your router forwards all requests on port 80 and 443 to your reverse proxy. The reverse proxy takes requests for subdomain1 and forwards it to the associated ip/port locally.
Can you set a port on DNS services that don’t typically use an SRV record (like Minecraft does, for example)?
I think I tired to figure this out once but couldn’t get it to work with web browsers. Ended up just looking at the HTTP request to find the subdomain and then routed from a reverse proxy as appropriate…
jws_shadotak@sh.itjust.works 1 day ago
I have a reverse proxy set up already. The path from the outside goes:
DNS -> my IP -> reverse proxy -> server
I’m just wondering what happens when my own devices on the same network go to the domain.
CameronDev@programming.dev 1 day ago
Devices on your domain will typically do a DNS lookup, which gets your public IP. Then they connect to that public IP, which your router recognises and redirects back into your network. The router then forwards that to your reverse proxy.
If your router isnt doing that properly (timing out usually), look up a setting usually called “NAT loopback” or “NAT hairpinning”. Thats the setting that detects your public IP, and redirects it back inward.
lyralycan@sh.itjust.works 1 day ago
Also if you have your own net filter like PiHole or AdGuard Home with DNS rewrites set up, and you use it as a DNS server in WiFi settings, then it works a small bit differently. A public IP and NAT routing is never needed, as the device contacts the DNS server via the router Access Point, and the DNS server translates the service’s FQDN into its internal IP. Aside from that, provided everything is set up correctly, all actual data packets go from device ←→ router ←→ service
CameronDev@programming.dev 1 day ago
I had issues with that recently, I had a few of my internal services set to resolve internally, but pihole was making a mess of them and returning IPv6 addresses in addition to the IPv4 internal addresses. And then browsers would try use the broken ipv6 address and fail. I just happily rely on hairpinning now, it hardly makes a difference in the scheme of things.
floquant@lemmy.dbzer0.com 19 hours ago
You already have a bunch of NAT-level suggestions, so I wanted to mention there’s an alternative solution: split-horizon DNS, or simply split DNS. Basically, you run a DNS server in your LAN (like pi-hole) which resolves to the private IP, so resolving externally and internally give different results. This way packets don’t hit the router at all. You can also do a wildcard like
*.something.lanto avoid having to add a record for every service, and only configure your reverse proxy.en.wikipedia.org/…/Network_address_translation#NA…
TL;DR Your router sees you trying to reach your externap address and routes the connection back to your LAN without leaving the network.
This does still depend on a functional internet connection however, as your client gets your public IP from a public DNS server over the Internet.
If you were to run a DNS server locally (I use pihole for this), you could have that DNS respond with your local IP, allowing clients within your LAN to resolve the name without needing to reach out to public DNS. This means your local connections will still work when your internet is down; it also provides more privacy by keeping those requests local and can let you make local-only names that aren’t publicly listed.
Of the ~28 FQDNs in my setup, only 4 are public. The rest is local/vpn only and not publicly listed due the above. The reverse proxy then drops all connections that don’t use one of those recognised names, before even completing the TLS handshake. (So direct connections from someone port scanning my IP or using a domain name someone else has pointed at my IP are completely ignored/dropped without response. The server doesn’t even send the TLS cert so as to not expose the names defined in it.)
NarrativeBear@lemmy.world 1 day ago
What you are looking for is something called NAT Reflection/HairPin NAT/NAT loopback.
When you search for a “domain.example.com” your router loops you back at your reverse proxy and all the traffic remains “internal”. Your website will still be externally accessible (the ones you setup to be).
Here’s a example of how to set this up on PfSense router.
www.youtube.com/watch?v=ngwae1UvS-Q
folekaule@lemmy.world 1 day ago
Your diagram is almost right, but I think it will help to understand more of the details. It’s important to understand the difference between DNS (domain name lookup) and IP routing.
To break your diagram down more, this is what happens when any computer looks up your website:
That’s all very simplified, of course.
As others pointed out, things may seem to work differently from the “inside”, if hairpinning is not available or enabled. This is not related to DNS, but to IP routing. The firewall doing NAT can get confused and not know what to do when an internal request goes to an external IP that it itself has. When it turns that around and routes it back to the internal network, that’s called hairpinning.
One “fix” for this, often used in enterprises, is to use so-called split DNS. All that means is that if you’re asking your internal DNS server for an internal name, it will give you the internal address (192.168.1.123 for example), but an external client would get an external IP.
TL;DR: DNS and IP routing are separate concerns and happen at different parts of the TCP/IP stack.