Using the Internet without IPv4 connectivity
A few days ago my ISP broke the IPv4 connectivity from my router after a power cut. Fortunately IPv6 connectivity still worked fine, but only a small fraction of websites were accessible.
In this post I'll cover how Linux, WireGuard, and Hetzner came to the rescue - keeping the whole internet usable with only an IPv6 connection.
Opinions expressed are solely my own and do not express the views or opinions of my employer.
Background
One morning I woke up with no power, and noticed the breakers had tripped. After resetting them, everything went back to normal - except I couldn't connect to GitHub and many other websites.
During the process of contacting my ISP, I realised the issue was only with IPv4 servers. I could connect fine to IPv6 servers - and this explained why Google and Meta worked fine, but many websites didn't. ping -6 and traceroute on both my machine and the router's diagnostic page confirmed this immediately. It seems this was an issue with the Carrier Grade NAT (CG-NAT), and this is why only IPv4 was affected.
Unfortunately, the ISP said they might need to send someone and it would take several days, after the weekend too. Meanwhile I needed to be able to access work, and my wife needed to finish her thesis, so just leaving it broken wasn't an option.
Fortunately, I remembered I had a Hetzner VPS server with both static IPv4 and IPv6 addresses. And luckily, the Hetzner website supports IPv6 so I was able to access the console there to set things up.
But first we need to understand what Network Address Translation (NAT) is.
... continue reading