Wednesday, January 04, 2006

IP Addresses

Heidi asked a question about IP Addresses and how to tell if similar addresses are the same user. Well I tried to fit an answer in the comments section but it is bigger than will really fit so I am going to post it.

The current addressing scheme is called IP4. It has 4 groups (octets) of 8 bits. Those 8 bits can equal 000 to 255. In theory then, an address can be between and Thus one might have an address that looks like this. Theory is nice and all, reality is pretty much always different.

Reserved Numbers
There are several ranges of Addresses that are reserved. the whole 000.x.x.x and 001.x.x.x ranges are reserved for the military. 10.x.x.x and 192.168.x.x are reserved for private use. 240.x.x.x to 255.x.x.x are all reserved for expirementation (what a HUGE waste!) The remaining addresses are Public addresses

With the above ranges taken out there are still a lot of addresses left. But today, need for physical addresses far exceeds actual addresses. This causes us to use various methods of tweaking to get addresses to each computer, and those methods may be covered in a later post, and cause what is seen by an IP tracker (such as Sitemeter) to only see one IP address for an entire business or even an entire ISP. For example, I may have 200 or 2000 computers at my business but only one Public IP address. So if John and Sally from BigEvilCorp comes to see your blog they will show up as the same IP address even if they are on different computers.

So if you see an address that is similar, say and you are seeing two different companies/ISPs that could actually be half a world apart.