Hi Folks,

A recent block and forum on how to use IP check has raised some questions on IP addresses.

This blog is to correct some misunderstandings on what IP addresses are, what they show, and what they mean.

Note: This blog is based entirely on IPv4 except the end. IPv6 aint common enough to be a factor at the moment yet. Don't ask about IPv5, it is something different altogether.

This blog doesn't also deal with any single person's situation, and doesn't come to any judgement on any. Its just a primer to help the general community understand.

What is an IP address

IP addresses are numbers that identify computers on a TCP/IP Network, like the internet. They look like four groups of numbers sperated by dots. Like this:

Each number is between 0 and 255, so in theory there are are 256x256x256x256 addressees. I make that 4 294 967 296. Seems like a lot right? Well its not.

In theory, each single computer gets an IP address. These are grouped into networks, so that and should be on the same network. In the good old days, when things were easy and we thought the internet would never be as big as it was, they were.

What would happen is a company would buy a big block of IP addresses. You could buy a class A block which means only the first number is set - Ford have a Class A block, and own every IP address between and

(The more technical who are skimming this are probably laughing because both of those addresses can't exist... but to make this easier, we're going to skip over that, mkay?).

If you weren't quite that big, you could get a Class B address, where just the first two blocks were set (like 130.132), and you had all the numbers starting with those two, or class C, where you had 193.167.142 given to you, and you had all the numbers that started with that.

But there's a problem with that. This means Ford have at their disposal, in theory at least, 256*256*256 IP addresses - 16 777 216 IP addresses. When they bough their block in 1995, they probably didn't have 16 Million computers, and probably still don't (Ford only have 224 000 employees!). But hey, when you have 4 billion IP addresses and the internet is just for geeks, who cares, right? Apple have a block the same size. So did Stanford University, Hewlett packard, and MIT... and I don't think any of them have 16 million computers either.

Well, there was a big problem - we started to run out. You can't buy a class A address anymore, heck, we even stopped assigning classes altogether. Companies are now encouraged to buy just what they need, but what organisations already have, they get to keep (although Stanford are among those giving up what they don't need anymore.

So, back in the good old days, your computer had an IP address. And it was stuck to that computer, and it never changed. And it was good... Until people started to want to connect from home.

Enter the home ISP

Any of you remember dial up? No? Well once upon a time to connect to the internet, you needed to make your computer make a phone call - you weren't just always connected.

This was great for ISPs. For every phone line, modem, and IP address they had for customers, they could get 10 or even 20 customers, and people still probably wouldn't ever get an engaged tone.

So what would happen is the ISP would rotate their IP addresses around their customers, and if a customer really really wanted their own IP address, they'd charge them extra money for it.

For some reason, even though we all have always on broadband, the idea of rotating IP addresses and charging for them stuck - pretty stupid if you ask me... if you expect all of your customers to always be on, you gotta have an IP address for each of em. But I digress.

Of course, back then we had wired "Modems" and we only had one computer... So the computer would get that rotating IP address that might rotate sometimes if you turned everything off and on again, but probably not if you didn't.

And that wasn't too bad. We started worrying about maybe running out one day, but who needs more than one computer?

Internet is Business

So, businesses started realising that this internet wasn't a fad after all... and having just one Internet connected computer was bad because their customers all of a sudden wanted to Email them... Shock horror.

These businesses didn't want an IP address for every computer - just like in many businesses each staff member doesn't even have their own phone number, just a main number that puts people through to the right extension there didn't seem to be much of a need, and in any case IP addresses were getting expensive.

So we came up with this thing called NAT. Basically, one router is given an IP address and it acts like a switchboard. It gives each local computer a "local" IP address that only works inside that business, and to the outside world everything looks like it came to or from that IP address the router has.

Its not great, and can be a pain in the ass if you've ever tried to run a server with it, but it meant that hundreds, or thousands of computers could share an IP address, as long as they wanted to do boring stuff like surf the web, and access email.

Then we all decided that having one computer wasn't enough. We wanted the kids to have their own so we could get some work done whilst they spent all of our money buying World of Warcraft gold. So NAT and Routers came into homes, and then we stuck wireless on em cos we didn't like tripping over cables.

But still, the IP addresses kept running out....

My IP address is 10.x.x.x or 192.168.x.x, My router, or my computer says so

Nope, it isn't.

Those are "Local" IP addresses... Like extension numbers I mentioned before. You can read your IP address from your router direct (it should be listed as external or WAN IP address or similar), or by going to a site like

Mobile Phones

Eventually we all decided that being connected at home wasn't enough. So we bought these magic speaky boxes that allowed us to talk anywhere we liked, and eventually put internet in em. At the start it was pretty shit, but eventually we managed to get it to work and look ok most of the time.

But there was a problem. You see, we already knew that IP addresses were running out, and we know we didn't have enough for one per magic speaky box.

So we souped up NAT.... Connecting thousands of phones through a single IP Address... and again, it works, as long as you don't try to run a server (and believe me, people have tried and complained).

But its still shit.

Are you going somewhere with this?

Yeah. This is what I'm getting to. Your IP address isn't your IP address anymore.

  • Did you connect at home to the wiki? Did you kid bro connect too? Then yep, you shared an IP address.
  • Did you connect at school or work? Did someone else? Yep, linked again.
  • Use a cellular (or if you're rich, Mobile satellite) phone connection? Gawd only knows who you're linked to.
  • Did noone else use your home connection but you, but then you rebooted your router - Could then be linked to someone else

So wait, does this mean IP check is useless?


IP checks are good for reasonable suspicion. Lets face it, we get around a million page views per day. Not all of these are going to be different people. The chances of someone using your IP address and accessing the wiki on the same day aren't great. Even if that IP address can be traced to a cellular company.

If you're linked on an IP to someone who used that IP a week or a month later, that aint telling us much.

It isn't a fait accompli... But the burden at this point is probably on you to show its not you.

So I think you made a mistake in blocking me...

If you're linked to another account in a very short period of time, you're going to probably have a hard time explaining it.

To help present your case, you're going to need to be able to account for where, and when, you used the wiki on that day.

To find your current IP address go to

  • When did you access it on a phone? Who is your provider? Can you remember when?
  • Did you access it at work, School, or another shared connection? When? Where? Do you know the ISP? Do you know that IP address? Can you find it out?
  • What is your home IP address now? Who is your provider?
  • Who else has access to your connection, is your network secured?

So, um, what are we doing about the running out of IP Addresses problem?

Well, in Asia they're already out of new IP addresses, and this problem is going to hit America and Europe soon. Africa's still got plenty for now.

We're supposed to be moving to a new system called IPv6. If memory serves, its going to leave us with more addresses than atoms in the universe... so good luck using them all. However getting all the companies and institutions to do it is a bit like herding cats. We all know theres a problem, we all know what needs to be done, but noone wants to do it until they can make money off it.

Changing ISP? Make sure you ask if your ISP supports IPv6. If it doesn't support IPv6, then they're not giving you access to all of the Internet.