Dynamic Host Configuration Protocol (DHCP)

DHCP Overview

DHCP stands for Dynamic Host Configuration Protocol. But what does that mean for the users of a network? It means that when everything is working correctly, you should be able to connect your computer to the data jack on the wall with an Ethernet cable, and the University's computer will recognize your computer and allow it to join the network.

IP address stands for Internet Protocol address and is four sets of up to three numbers, separated by dots (128.255.123.76, for example). It works much like a phone number for the Internet so that computers can communicate with each other. Before DHCP, you would have had to type in a static IP address, 12 numbers that would be your "address" on the Internet. Configuring computers was more difficult and distributing unique numbers was a large organizational problem. DHCP allows IP addresses to be automatically assigned, instead of having to manually type them in.

DHCP Troubleshooting (Renew and Release IP Address)

Sometimes computers have networking problems that can be attributed to DHCP. In such cases your computers isn't able to receive a valid IP address from the DHCP server. When your computer is unable to contact the DHCP server it usually assigns itself an IP address like 169.x.x.x (which means your computer can't connect to the network). The following instructions describe how to check your IP information as well as how to receive a new IP address from the DHCP server. In some cases performing a "release and renew" on your IP information can clear up the problem and restore your Internet connection.

Before attempting to troubleshoot DHCP, make sure that the Ethernet cable is connected at both the computer and the wall jack and that the lights on the Ethernet card light up (if there are lights on the card). A DHCP problem usually means that there is no network connectivity for the computer at all. If your computer can connect to certain services but not others, please call the Help Desk at 384-HELP wand we can assist you in finding the problem. See the specific instructions for your computer's operating system below. (Click here for Mac OS instructions or here for Windows 95/98/ME instructions.)

 

Windows Vista, XP, and 2000

This method uses the command line interface of the Windows OS. To release and renew your IP address, follow the instructions below.

  1. Click on Start | Run.
  2. Type cmd and click OK.
  3. Type ipconfig and press the enter key. Windows will now display your information about your IP configuration.

    ipconfig

  4. If you are experiencing problems with your Internet connection, try to release and renew your IP address. This is accomplished by typing the following command: ipconfig /release. Make sure to type a space after ipconfig and a forward slash before release. 
  5. Once you have released your IP address you need to renew it by using the command: ipconfig /renew. (Again, remember the space after ipconfig and the forward slash before renew.)

If you are still unable to connect, write down your IP address and contact the Help Desk at 384-HELP.

 

Macintosh Operating Systems

In both Classic and OS X (before OS 10.3), the simplest way to release and renew your IP address is to restart the system. To check your IP information, or refresh the settings without rebooting in OS 10.3 and above, follow the directions below:

Mac OS 10.3 and Above

  1. Launch the System Preferences applet from the Apple Menu.
  2. Click on the Network icon under the Internet and Network heading.
  3. Make sure your network card is selected in the Show box.
  4. Click Renew DHCP Lease.

Mac OS 10 (Before 10.3)

  1. Launch the System Preferences applet from the Apple Menu.
  2. Click on the Network icon under the Internet and Network heading.
  3. Make sure your network card is selected in the Show box. The IP information will be displayed below.
  4. To release and renew your IP address, select the TCP/IP tab and select Manually from the Configure selection box. Type in the following information: Set the IP address to 10.0.0.1 and the subnet mask to 255.255.255.0, then click on the Apply Now button.
  5. Select Using DHCP from the Configure selection box and click Apply now. The system should now attempt to get an IP address.

Mac OS 9.x and Earlier:

  1. Click on the Apple menu and select TCP/IP in the Control Panel Folder.
  2. When the TCP/IP control panel opens, select your network card from the Connect Via box. Your IP information will appear below the selection box.
  3. To refresh your DHCP settings, select Manually in the Configure selection box. For your IP address enter 10.0.0.1 and under subnet mask enter 255.255.255.0.
  4. Close the control panel and click Save when prompted.
  5. Reopen the control panel (follow steps 1 and 2) and this time select Using DHCP Server in the Configure selection box.
  6. Close the window and click Save.

If you are still unable to get connected, write down your IP address and contact the Help Desk at 384-HELP.

 

Windows 95/98/ME

Windows 95, 98, and ME use a tool called winipcfg.exe which allows you to see and control some of the settings for your networking resources. To check your IP information as well as release and renew your IP address.

  1. Click on Start | Run.
  2. In the text box, type winipcfg.exe and click OK. The program will launch.
  3. In the selection box, make sure that your Ethernet adapter is selected. Basic IP information is displayed, to see an expanded view click on More Info.

    IPConfig

  4. To release and renew your IP address click the Release button. The system will pause for a moment and then click on Renew. The expanded view of winipcfg is shown, but this can be done from the normal view.

    Renew IP

If you are still unable to get connected, write down your IP address and contact the Help Desk at 384-HELP.

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