Using the Internet without IPv4 connectivity

Summary

Using the Internet without IPv4 connectivity 2025-06-27 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. Network Address Translation (NAT) Internet Protocol (IP) addresses are used to specify the source and destination of IP traffic. Much like a letter with a return address, you send a packet to a server with its IP address (perhaps resolved from a domain name) and it will send its reply back to you from the source address on the packet it received. However, IPv4 addresses are onl...