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Monday, 14 February 2011

IPv4, IPv6, what's all that about and why should I care?

IPv4 and IPv6 - hmmm, sounds about as interesting as reading the yellow pages, doesn't it?  Well, yes, I guess so, but looking forward it will has as much impact as the change from analogue to digital TV.  In a way, it's kinda similar too.

Let's start with a quick explanation of what IPv4 is and why it's changing to IPv6.

Every computer, smartphone, tablet or Internet connected device has an Internet address, or (IP address as they are more often known).  This uniquely identifies it over the internet.

Wowsers, I hear you say that's a humongous number of IP addresses - well yes and no.  The vast majority of computers attached to commercial networks re-use IP addresses from a limited pool that are not exposed to the outside world, greatly reducing the IP addresses hoovered up by such organisations.  Chances are that if you have more than one computer, smartphone or tablet device at home, you will have the same technology that uses internal routed IP addresses, but only one external address.

So, what does an IPv4 address look like?  They are a series of 4 numbers separated by a point.  For example, your home broadband router will likely have an IP address of, or or similar.  The range is reserved for non-routable addresses, i.e. addresses that are not publicly exposed.  So your PC might be and your neighbour might also have the same IP address for his PC too.  You will both have different external IP addresses however, using the same format and allocated by your ISP.

Now a quick inspection of the IPv4 format shows that the number of addresses available is 4,294,967,296 - which is a very big number.

Unfortunately, not big enough.

Even allowing for the hoards of corporate machines hiding behind their internal IP addresses, the range of IPv4 addresses recently ran out.

Did you notice the sky falling in?  No?  Well neither did anyone else, because although the last 5 blocks of numbers were allocated on 3rd February 2011, these allocations, together with myriads of others have not been fully taken up by end users.  But time will come when they will and the world as we know it will come grinding to a halt.

Well, not exactly.  This is where IPv6 comes riding like the 7th Cavalry over the horizon to save us all.

IPv6 (don't ask what happened to IPv5!), is the successor to IPv4 and generates  an astronomic number of addresses - it has 128 bits, as opposed to 32 bits of IPv4.  This gives it approximately 340 Undecillion combinations (look it up if you are interested).  Suffice to say it's hugely bigger than IPv4.  It has a format similar to 2001:0db8:85a3:0000:0000:8a2e:0370:7334.

Great, all is fine and dandy in the world.  Errr, not exactly.  You see, IPv4 and IPv6 are not interchangeable and not compatible with each other.

Yikes, does that mean when the big IPv4 switch is pulled my computer will come crashing down.  Probably not.  Most modern computers are able to understand both IPV4 and IPv6 and many routers are too.  Also, it is very likely that your service provider may support a period of changeover of both IPv4 and IPv6 addresses allowing you to surf away without worrying about all those bit and bytes.  Some service providers may even go far enough to provide upgrade routers that are compatible with IPv6 if your current router isn't already, though whether they give them away free or charge for the upgrade remains to be seen.

For those really interested there is a world IPv6 day on 8th June 2011 when major service providers and some website companies will be testing their readiness for IPv6.  You can also find more information about IPv6 readiness here but remember that it will almost certainly fail as of now since IPv6 is not actively being rolled out to end users in most circumstances.

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