An IP address (Internet Protocol address) is a unique number that devices use in order to identify and communicate with each other on a network utilizing the Internet Protocol standard. For example, your computer has a unique IP address on ResNet. It is obtained during the ResNet Registration Process.

If you're having problems connecting to the internet at Carleton, an easy thing to check is whether or not your machine has an IP address. If it doesn't, it will not be able to use any of the network services (Internet, E-mail, network drives).

Reading your IP Address from

For any on-campus system, IP address and MAC address should appear at the bottom of

This is usually easier than running OS-specific commands, below.

Finding your IP address


  1. Click on the Start menu.
  2. If using Windows XP, click "Run...". Otherwise, go to the next step.
  3. Type "cmd" without quotes.
  4. In the window that opens, type "ipconfig /all" without quotes. You may see a lot of output similar to that below.

    You are looking for one of the options outlined in red based on the type of connection you are using ("Wireless" or "Ethernet"). Your IP address is on the line labelled "IPv4 Address", outlined in green.


  1. Press cmd + space or click on the Spotlight magnifying glass in the upper right and search for "Network Utility".
  2. In the window that opens, look under "Interface Information" for "IP Address", as shown below.

    The number listed is your IP address. Note that you may have to change the drop down selection to reflect your type of connection ("Ethernet" or "Wi-Fi").

Using your IP address to diagnose a connection issue

Your IP address should give a good idea of what's going on with your computer. Firstly, determine whether your IP address starts with 137, 10, 192, 169 or 0.

General troubleshooting: Are you getting link lights? Link lights, the small lights on your ethernet card, when lit, mean that there is a link between your computer and the network. Some cards combine the link light and the traffic light: if everything is working, the light will be solidly lit most of the time, but will blink when it sees traffic on the network. If there are no link lights, there may be a problem with the ethernet card. Check the network adapters in the Device Manager (Device Manager can be found under the Hardware tab when you right click My Computer and select Properties) - look for yellow exclamation points or question marks that point to hardware problems. Do new drivers need to be installed? Is the hardware lodged firmly into the computer? Malware is also known to hamper internet connectivity: be sure no viruses or spyware are ruining computer settings. Is it a port problem?

Resetting the TCP/IP Stack (outdated, Windows only)

For 169 and 0 IP addresses, you can try resetting the TCP/IP stack:

  1. Do so by opening a command prompt (Start>Run>"cmd")
  2. Type the following command (sans quotes): "netsh int ip reset resetlog.txt" .
  3. If that command doesn't work, another command that is supposed to work under Windows Service Pack 2 is: "netsh reset winsock catalog" .

External Links

Registration Page

For more information on IP addresses, try wikipedia: IP Address