6to4 addressing

6to4 addressing is a way to use one internet IPv4 address to connect to any IPv6 host.

How to use IPv6 right now

 * I attempt to explain how to use IPv6 in a home environment, like mine.

You can use IPv6 right now, but let's take a step back for a moment. You are using the internet via IPv4 now, which means you must have an IPv4 address. Where did that address come from? You did not choose it yourself, it was assigned to you by your ISP—your Internet Service Provider. This is natural and happens every time. There is a central registry—the IANA—which manages all the internet addresses, but you don't have to deal with them, your ISP takes care of that.

There is one more wrinkle I should mention. If you are using a home router to 'share' or 'split' your internet connection to multiple computers, your computers will not have internet addresses, they will have local-only addresses, which only work within the small network in your home. This means you are not really on the internet—honest!—and you will not be able to use IPv6 as I am about to describe.

6to4 addressing
6to4 addressing is really cool—it allows you to connect to the IPv6 internet with only your IPv4 address provided by your ISP. It's free, and it does not require any support or configuration by your ISP. However, it is tricky to set up. It seems there should be some kind of auto-setup script for Linux distributions, but so far, i have found nothing.

Setup
First, find the IPv4 address of your external interface. Easiest is to use ifconfig.

Then, use the following magic script to generate the 6to4 IPv6 address you will use to connect to the IPv6 internet. Insert your IPv4 address in place of 1.2.3.4. Create a new tunnel device. TTL could be more or less, but 64 is a good default Bring interface up (turn it on) Add the generated 6to4 address to the tunnel interface (note: prefix length 16 is important!) Add (default) route to the global IPv6 network using the 6to4-gateway IPv4 anycast address of 192.88.99.1

If you got no errors on any of those steps (and you entered all the addresses correctly) you should be able to try: You well get replies, as shown, if it works. This site is in Japan, and if you can ping it, you're on the IPv6 Internet!

Providing an internet gateway with IPv6
There is a seperate document explaining the setup of a 6to4 gateway router, which allows one 6to4-enabled host to provide IPv6 connectivity to a massive number of internal hosts. Using IPv6, of course.