No-IP provides a dynamic DNS service. When you connect to the Internet your ISP assigns an IP address to your computer (or router if use one). The technical term for the process is Dynamic Host Configuration Protocol usually abbreviated as DHCP. The easy way to determine your IP address is to visit a web page such as ipbrowser.net that bounces it back to you. If you are running some sort of server software that allows friends to access your computer, they must know this address. The problem is that this address may change from time to time, for example, if your provider experiences a power outage and must restore its connections.

A dynamic DNS service provides a solution to this problem. You are provided with a static (unchanging) domain name. If your IP changes, you update the service but the domain name is unchanged. The friendly folks at no-ip.com will give you a free domain name. Of course, there some limitations to a free account but for our purpose they do not apply.

Your first step, therefore, is to sign up for a free account and a free domain name. Your next step will be to install an updating client and configure it to start at boot time. This procedure will vary by your platform. I will describe how I did it on my Ubuntu Linux machine. Look for “noip2″ in the repositories with Synaptic and install it. The installation will automatically bring up some configuration options. You will need to input your static domain name, a password chosen by you when you registered an account at no-ip,com and the interval at which you want the DNS server updated. I chose 30 minutes. Take the option to run at boot time and DO NOT disable NAT if you are behind a router.

The service runs as a daemon (background process). To test that it is running, bring up a terminal and issue the command “sudo noip2 -S”. You can reconfigure the client with the command “sudo noip2 -C”.

Do you see where this going? Suppose you have done all of the above on a laptop and suppose your static domain name is “myname.no-ip.biz”. One day your laptop is missing. You then go to any convenient computer, bring up a terminal and “ping myname.no-ip.biz”. If the laptop is connected to the internet its IP address will be returned. It’s location can be determined with the cooperation of a legal authority and the ISP that owns the IP address you determined!

Obviously, this will not work if the laptop is not connected to the Internet and several attempts may be necessary before any useful information is obtained. However, it’s free and just might of invaluable help one day.

A note about the ping command. This command does not automatically terminate when issued. It will reissue itself every few seconds until stopped. Stop it by issuing a CTRL+C before closing the terminal window.