How does he change his I.P. so much? I understand you can use something called 'dynamic i.p.' but I'm not really sure how to do it. So you know its him because the first 6 numbers are the same?
dynamic ip's are based off of your service provider. Lease time is the time for which the IP is valid. After the lease time expires, a fresh IP is issued to you.
Assigning the IP address is dependent on the server. It may be random or it may have a pattern. Generally its random. As such everytime someone resets their computer/router they are generally assigned a new IP bc their old one was given to someone else. Its really annoying for tracking hackers. We have one on Evil servers who's ip's range from 68.xx.xx.xx-72.xx.xx.xx.