I Get an Error Message Telling Me That Multiple Devices Have the Same IP Address

When I attempt to start up one of the devices on my network, I see an alert stating that a device has already been assigned the IP address and that IP services are being shut down. How do I correct this problem?

Two devices on the same network cannot have the same IP address. If you start up one device and see this error message, you have two or more devices trying to use the same address. Check the configuration of each device to see which devices are using that address (for Mac OS X machines, use the TCP/IP tab of the Network pane of the System Preferences utility to see how the computer is configured). Make sure that each device has a unique address, including an AirPort Base Station or other device that is sharing the account.

Occasionally, your hub will "remember" the devices that are using specific IP addresses and you will see this error even though you made sure that each device had a unique address. If this happens, power down your entire network, including the hub and all other devices attached to it. Wait a few minutes and power up everything again. The error should be cleared as each device registers its unique address on the network.

None of the Computers Can Access the Internet

When I attempt to access a service on the Internet, such as the Web, I get an error message stating that the resource can't be found. Why am I getting this error?

Troubleshooting a network connection to the Internet can be quite challenging. Your approach should be to eliminate potential sources of the problem one by one until you find the specific problem you are having.

If you are unable to connect to the Internet after you have installed and configured the hub, try the following steps:

  1. Remove the hub again and return your configuration to the way it was before you installed the new hub.

  2. Return one Mac to the condition it was in when you were able to access the Internet.

  3. Check to see whether you can access the Internet. If you can, that means your modem is working properly and the configuration information is correct.

  4. Attach that single computer and your modem to the DHCP hub again. This removes potential causes of problems that are due to the interaction of devices on the network.

  5. Repeat the hub configuration and verify that the settings match those you used to connect the single Mac to the Internet.

  6. Set the TCP/IP settings on the Mac to use a DHCP server.

  7. Try to connect to the Internet. If you can connect, add your other machines back to the network. If the problem recurs, you know that it is related to interaction among the devices.

  8. In some cases, you might need to configure your hub to use MAC address cloning. A MAC, or Media Access Control, address uniquely identifies each node on a network. In some cases, you will need to clone, or copy, the MAC address of one of the computers on your network onto the router. See the instructions that came with the hub to learn how to configure MAC cloning on your router.

  9. If you still can't connect, call your ISP for support.


Some broadband providers support only one computer for each IP address or DHCP name for each account. In these cases, you might have to purchase additional addresses in order to be able to share a single account.


You might be able to share an account using a software DHCP server even if you can't use a hardware device to do so. For example, try using an AirPort Software Base Station to share your account.

    Part I: Mac OS X: Exploring the Core
    Part III: Mac OS X: Living the Digital Lifestyle