There are two types of IP addresses for most home users. The first and most common is the Dynamic IP address. In this scenario your ISP (cable or DSL provider) assigns a dynamic IP address via DHCP. Your address can change based on time (aging) or when your equipment is reset or unplugged. One reality is that many times the service provider maintains a map of your MAC to IP address on their equipment, and you tend to always be re-assigned the address that you had previously when a look-up is performed. With Time Warner Cable, our household has had the same IP address for over three years.
The second type of IP address is a static IP address in which a permanent address is assigned to your connection. Static IP addresses are usually associated with business connections where the user is running a mail or web server that needs a permanent IP address. Most home connections do not use static addressing unless you specificly request it and pay for it.
- Greg