Since I have moved house, the web server for axotron.se also had to move. Unfortunately it was not quite as much plug-and-play as I had hoped, so the move resulted in a few days of downtime. The main problem was that I had to ask for a unique public IP address from the service provider Bahnhof and that I did not realize that the IP address I otherwise got was not unique for me (how does that work?).
Anyway, their support fixed the IP uniqueness problem while I talked to them today and now everything seems to be up and running again.
Your ISP probably by default hands out private IP addresses and employs NAT to let you access the internet. That lets them serve multiple customers per public IP address. The same thing happens locally where your router serves multiple local clients using one external IP address. So basically an internal client is then double NATed, first by your home router and then by your ISP.
Hi Danjel,
Thanks for pointing that out. I did not think about NAT when I wrote the post, but it seems reasonable that standard NAT is what they are using. Without port forwarding (which they of course cannot do since they do not know what ports different users’ servers might need and that several users might even need the same port), it is impossible to get a web server to work.
NAT has always seemed like a bit of magic to me by the way… Probably since I do not know enough about the inner workings of network protocols.