(If you are wondering whatever happened to IPv5 then look here)
The good old IPv4 address that we all currently know and love (and understand, I hope) is basically a 32 bit number divided into four 8 bit "octets".
That gives us a theoretical address space of 2^32 (4.3 billion) addresses.
On the other hand, IPv6 uses 128 bit address's represented as eight groups of four hexadecimal digits, each group representing 16 bits (two octets)
This new address space supports 2^128 (340 undecillion) addresses which is more than we will ever conceivably require on Planet Earth.
Right now you are probably thinking "Yeah, I've heard that before about 640K RAM and we all know how that one worked out" so to put the sheer size of the IPv6 address space into perspective let me quote an excellent IPv6 primer over at Ars Technica, "there are currently 130 million people born each year. If this number of births remains the same until the sun goes dark in 5 billion years, and all of these people live to be 72 years old, they can all have 53 times the address space of the IPv4 Internet for every second of their lives."
Now, I'm sure you'll agree, that is a lot of addresses.
For a good overview of how IPv6 addressing works, I recommend this article.
After reading up a bit about IPv6 you could be excused for concluding that the whole idea of IPv6 is quite daunting and then push the whole damned thing into the "too hard" basket. This is what most people and organisations have been doing up to this point and explains why adoption rates are currently so low.
ISP's in particular are putting off the inevitable by hoarding blocks of the remaining IPv4 space.
Don't be put off by the apparent complexity of IPv6 though!
In practice it is in fact not that hard to get up and running, even if you don't completely understand how it all hangs together at first. I still haven't figured it out properly, but soldier on I will!
As they say, practice makes perfect and this is the intention of the series of articles I will be posting on getting up to speed with IPv6.
Note: A word of warning, these articles are intended to be used for educational purposes only. Because we cannot use an IPv6 address range of our own we are going to be obtaining one through what is known as an "IPv6 Tunnel Broker". This is of course not an ideal situation because we are going to be relying on that broker for all of our IPv6 addresses and routing. I do not advise that you configure a production network for IPv6 connectivity using this guide as you will surely face performance penalties, possible reliability issues, and (most importantly) future migration issues when your ISP eventually starts providing you IPv6 directly. If you are intending to roll out IPv6 in a production scenario I suggest that you choose an ISP that is already providing native IPv6 to their customers.
Next up, Setting The Stage