Dynamic vs. Static IPs

[Red Shirt Volunteer 0]

As some of you may know, a lot of ADSL ISPs give you a dynamic IP, meaning that it changes every time you connect to the Internet. Some people pay for a static IP. There are reasons why you would want one of each, but that's not important here. Using Windows (at least on XP), you can force a static IP and decide which address you want to use. Sometimes I want a specific IP. My questions to anyone who knows about this are as follows:

 

1. How are dynamic IPs generated?

 

My guess is they come from a blocked list of IPs assigned to particular ISPs.

 

2. If I designate an IP using my OS, am I taking someone else's and causing them problems?

 

I'm assuming no because it's random. Sometimes someone else is using that IP, so I can't connect, in which case I always fall back on the dynamic selection.

 

3. Is it legal to designate your own IP using your OS?

 

I don't know about this.

 

Thanks for any help you can offer,

 

Red Shirt Volunteer