DHCP Primer Page 2 — Location, Location, Location An IP address is like your telephone number or your home address -- each one is entirely unique. Every computer on the Internet has its very own IP address. The standard format is four groups of numbers separated by periods, and each number is an integer between 0 and 255. For example, a typical IP address would look like this: 181.255.107.4. If you know a computer's IP address, you can reach out and touch it from anywhere on Earth. But since all those numbers are difficult for the human mind to keep at its neural fingertips, IP addresses are often assigned a human-friendly names, like www.webmonkey.com, which one of the Internet's battery of domain name servers translates into the proper IP number. IP addresses can be divided into two groups: static and dynamic. Computers that run important tasks all day, every day, such as Web servers and mail servers, have static IP addresses -- their addresses never change. Since these computers are always at the same virtual "location," they are easy to find. Most of the computers on the Internet, including the bedroom PC you use to surf the Internet, have dynamic IP addresses. Every time you hop on the Internet, your computer is assigned a different IP address by your service provider's DHCP server. You move to a new IP address every time you connect, but your DHCP server always knows exactly where to find you. Even if you say connected to the Internet all of the time, the DHCP server makes sure your computer gets a fresh new address every few days. Keeping IP addresses in constant flux is an excellent security measure -- just think about how hard it would be for the FBI to find you if YOU changed locations every three days. DHCP operates like any other client-server relationship. When your PC connects to a DHCP server, the server leases your computer a private IP address. Your computer lives at that address until the lease expires, at which point you are given a new IP address. When you configure your DHCP server, you can set the leases to time out at different intervals. The most common lease duration among ISPs and other large networks is three days. After three days, just like an all-knowing landlord, your DHCP server leases out a new IP address to your computer and redirects all of your traffic. No credit check or post office forms required! To next page of DHCP To last page of DHCP Back to the HTML Home Page