Finding a computer's IP address is easier than most users think and it can be a great tool for troubleshooting a computer's problems long before calling tech support.

One of the first things a user often hears upon calling tech support is "What is your IP address?"

The method for finding a computer's address varies depending on the type of computer involved.

Finding an IP address on a Windows Computer

On a PC (Windows) machine, the IP address can be found by first opening a command prompt. To open a command prompt:

1. Go to the Start button, and click it
2. Select "Run" from the menu and click it
3. In the box that appears, type "cmd" (without the quotes)

A black window should open up. This is the command prompt. To find out the IP address type "ipconfig" (without the quotes).

A few rows of data should appear on the screen. The line containing the IP address will be labeled "IP Address". The IP address is the number at the end of the dotted line. The format is 4 sets of numbers in this format: xxx.xxx.xxx.xxx. Each number should be between 0-255. Each "section" is called an octet, and all octets are needed for troubleshooting.

Finding an IP Address on a Macintosh Computer

On a Mac (OS X) the IP address can be located via the Terminal.

1. Open the Applications folder
2. From within the Applications folder, find and open the Utilities folder
3. Double-click the Terminal application to launch

At the command prompt, type the word "ifconfig". This results in a lot of data, so caution must be taken to ensure the right IP address is recorded. The IP address will be under a section labeled either en0, or en1, but NOT lo0. Beside the word inet is the IP address, in a xxx.xxx.xxx.xxx format.

Troubleshooting with the IP Address

Once the IP address has been recorded, there are a number of problems that can be determined by the IP address alone.

If the IP address is 0.0.0.0, the computer is still seeking an IP address (many computers seek an IP address from the network when they boot up). Without a valid IP address a computer cannot "talk" on the network.

If the IP address begins with 169.254.xxx.xxx, this means the computer has tried to find an IP address on the network but has failed, so it has given itself an IP address. This is also called an APIPA (Automatic Private IP Addressing) address. A computer cannot talk on the network with an APIPA address, and this is often an indication the computer cannot find the network or has no connection to the network.

Computers that are on a home network or behind a firewall may receive what is called a "private IP address". These are blocks of IP addresses that operate only in private networks and do not work on the internet. The IANA (Internet Assigned Numbers Authority) reserved these blocks of IP addresses for use in certain internet functions such as routing and device communication. Private addresses can be any of the following:

10.xxx.xxx.xxx

172.16.xxx.xxx - 172.31.xxx.xxx

192.168.xxx.xxx

If any of these IP address are displayed then further work will be required to determine the "real" IP address of the computer. Often, going to a website such as WhatsMyIP will reveal the IP address that is used on the internet. Having a private IP is not a symptom of any problem.

Having an IP address in hand is an excellent way to speed up a technical support call, and perhaps determine the problem ahead of time.