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Computer Clusters

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Network Connections for Your Laptop - in the Library

What is Roaming DHCP?

To connect to the campus network, each computer must be assigned an IP address, which uniquely identifies it on the network. These IP addresses are normally tied to your IP subnet, or physical location on campus - an IP address which works in Terman Engineering will not work anywhere in the Quad, for instance. You can either tell your computer its IP address manually, by entering it into the Network Control Panel (or equivalent), or through a service called DHCP.

With DHCP, when your computer starts up and is connected to the network, it sends its name to a central server, which then replies with the IP address assigned to your computer. Normally, each computer is assigned only one address, depending on where your "home" network is. Roaming DHCP means that your computer can be assigned different addresses based on your physical location.

What do I need to have in order to use Roaming DHCP?

You must be a Stanford student, faculty, or staff member. We're sorry, but at this point this service is not available to non-Stanford users.

In order to use DHCP, both the IP subnet (physical location) and your computer must be entered into the campus DHCP server as supporting roaming.

You must have a computer and operating system that is capable of running DHCP. Windows 95, Windows 98, Windows NT, or MacOS running Open Transport will all work with DHCP. You must also own an Ethernet card that is properly installed and configured for your system, and you will need to bring a 10-Base-T network cable to the library with you. A 10-Base-T cable looks much like a phone cord, only with larger connectors. You can purchase these cables at the Stanford Bookstore/Microdisc, or any computer supply store.

How do I configure my laptop for Roaming DHCP?

The library staff are not able to assist you with configuring your system - the necessary central changes must be performed by your Local Network Administrator (LNA). Students should contact their Residential Computing Consultant (RCC). If you are not certain who the appropriate contact is, you can find lists of LNAs online at, and RCCs at If your department does not have an LNA, or you are a student living off-campus, contact ITSS Customer Support at 725-HELP (4357).

When you contact your LNA, RCC, or ITSS, ask them to register your laptop for Roaming DHCP. They will ask you for certain information about your system, including the hostname, manufacturer/model, and the hardware or MAC address of your Ethernet card.

Your computer may already be configured to use DHCP, in which case you will not need to make any changes to your system. If you have previously used a manually-assigned IP address, you will need to re-configure your system. Directions are available online at, and your computer support people (LNA, Expert Partner, RCC, or ITSS Customer Support) will be able to assist you.

Before coming to the library to use Roaming DHCP, make sure that your newly-configured laptop works on the network in your "home" location (department, dorm, etc). Work with your computer support people to verify this, before attempting to connect in the library.

OK, I'm configured. How do I use it?

Bring your prepared laptop (with installed Ethernet card) and cable to this library, or one of the other participating locations. Ask the library staff where the network connections are located. Plug your cable into the network jack in the wall, and into the Ethernet card. Start up (or reboot) your computer - you should be online! You can use your network applications (Netscape, Eudora, Samson, etc.) as you normally would.

What do I do if I have problems?

The most common problem is that the central server insists on assigning your last-used address, instead of recognizing your new location and giving you a new and appropriate address. (This is called "renewing your lease".)

If you have properly plugged in and restarted, and are unable to see the campus network from your system, try renewing your lease manually. Here are directions on this procedure for various operating systems:

Windows 95

  1. Click on the Start Menu button and select Run...
  2. Type winipcfg into the box, and click the OK button
  3. Click on the Release all button
  4. Click on the Renew All button
  5. Click on the OK button to exit the winipcfg program

Windows NT/2000

  1. Click on the Start Menu button and select Run...
  2. Type cmd into the box, and click the OK button
  3. At the command prompt, type ipconfig /release, and press Enter key
  4. At the command prompt, type ipconfig /renew, and press Enter key
  5. Close the window


  1. Close any open Internet applications (such as Web browsers and email). Be sure to save any changes to any open documents.
  2. Choose System Preferences from the Apple menu.
  3. Choose Network from the View menu.
  4. Choose Active Network Ports from the Show menu.
  5. Deselect the "on" checkbox for port you use to connect to the Internet (such as Built-in Ethernet or AirPort).
  6. Click Apply Now.
  7. Reselect the checkbox for the port.
  8. Click Apply Now.
  9. Open a Web browser, and attempt to connect.

MacOS 9.x

  1. Close any open Internet applications (such as Web browsers and email). Be sure to save any changes to any open documents.
  2. Open the TCP/IP control panel.
  3. Choose User Mode from the Edit menu.
  4. Click the radio button for Advanced.
  5. Click OK.
  6. Click Options.
  7. Click the radio button for Inactive.
  8. Click OK.
  9. Close the TCP/IP control panel.
  10. When prompted, click Save.
  11. Open the TCP/IP control panel.
  12. When prompted, click Yes.
  13. Close the TCP/IP control panel.
  14. Open a Web browser, and attempt to connect.

MacOS 8.5

  1. Open the TCP/IP Control Panel
  2. Pull down the list box showing DHCP, and select Manual Address.
  3. Pull down the list box showing Manual Address, and select DHCP.
  4. Pull down the Edit menu and select User Mode. Make sure that Basic is selected.
  5. Click the OK button to close the Control Panel

If renewing your lease does not work, the library staff have a short troubleshooting list that they may be able to work through with you. However, please recognize that they are not computer specialists, and that networking is a dark and mysterious art. If you continue to have problems connecting to the network, contact your LNA, RCC, or ITSS, for additional support.

Please send inquiries about this page to:
Ronnie Fields

Last modified: July 7, 2006

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