well all in all, we've run out of ip address, thats why, back in the day, you had to specify what IP you were going to use with your cable account. I say cable because cable came before dsl, and well the cable companies would marry the mac address of your router to the ip address, however, after many millions and millions of people subscribing, then had to change that and make everyone use a dynamic ip address for cable, dsl, idsn(if thats still around) and even some t1's. Its all very sad but all in all, yes its true, your IP address does change once you disconnect.

However, if you are on a cable/dsl like and your not running your internet connection thru a router and want your ip address to change, just go to start/run type cmd then type ipconfig /release then wait a sec or two and then type ipconfig /renew and wait about 1 minute, then your ip address should change. Now you really only want to do this if your being attacked by hackers or something real silly. IDK, whatever =\

just a little
P.S. there is IPv6 coming out thats going to make it instead of 192.168.0.1 we are going to have 192.168.0.0.1 get it? xxx.xxx.xxx.xxx to xxx.xxx.xxx.xxx.xxx its funny how 3 more numbers makes the possiblites from 999 million different ip address to 999 BILLION address