Double-NAT and How to Escape It

Fri, 01 Mar 2024 15:52:00 +0000

You forwarded the port. You checked it three times. The service works perfectly from inside the house and is stone dead from the outside, and you’re starting to doubt your own competence. Before you rewrite the firewall rule for the fourth time, check one thing: how many times your traffic gets NATed on the way out. Because if the answer is “twice”, the port forward you configured on your router never had a chance — the packet gets translated again upstream by a device you don’t control, and your forward is pointing at the wrong layer of the onion. This is double-NAT, and it’s one of the most common reasons a home self-hoster’s inbound access mysteriously refuses to work.

Nat - vo.rs

Double-NAT and How to Escape It