This article describes how to troubleshoot problems with cable modems in Microsoft Windows XP.

Back to the top

Types of Cable Modem Services

There are two types of cable modem services: two-way cable modems and one-way cable modems. A two-way cable modem receives and sends information over the cable. A one-way cable modem receives information over the cable and sends information over the phone line.

Back to the top

Troubleshooting Cable Modem Connectivity

If you are unable to connect to the Internet by using a cable modem, you should first verify that you are not experiencing a cable outage. If your television has good cable reception and you are still unable to connect to the Internet using your cable modem, follow the troubleshooting steps in the appropriate section below:

Back to the top

Two-Way Cable Service

Two-way cable service uses a network adapter and a cable modem. You can use standard network connectivity troubleshooting to determine if the issue is a Windows XP connectivity issue.

For additional information about how to troubleshoot network connectivity problems, click the following article number to view the article in the Microsoft Knowledge Base:

Back to the top

One-Way Cable Service

If you are unable to connect to your cable company's Internet service provider (ISP), the connection is slow, or you connect but are unable to view any Web pages, use as many of the following steps as needed to resolve the issue. If one step does not work, proceed to the next step until the issue is resolved.

1.	There may be an interrupt request line (IRQ) or input/output (I/O) address resource conflict between your cable modem and another hardware device in your computer. This is usually indicated by an exclamation point in a yellow circle next to the device, or multiple incoming or outgoing cable modems listed in Device Manager. For additional information about how to troubleshoot resource conflicts using Device Manager in Windows XP, click the following article numbers to view the articles in the Microsoft Knowledge Base: 283658 (http://support.microsoft.com/kb/283658/) How to manage devices in Windows XP 244601 (http://support.microsoft.com/kb/244601/) How to troubleshoot unknown devices listed in Device Manager 310123 (http://support.microsoft.com/kb/310123/) Explanation of error codes generated by Device Manager 310126 (http://support.microsoft.com/kb/310126/) Troubleshooting device conflicts with Device Manager If multiple incoming or outgoing cable modems are listed in Device Manager, remove the duplicate modem entries, and then follow the steps in the article to troubleshoot the resource conflict. To remove duplicate cable modem entries in Device Manager, follow these steps: a. Click Start, click Control Panel, and then double-click System. b. Click the Hardware tab, and then click Device Manager c. Double-click the Modem Branch to expand it. d. Click a duplicate cable modem, and then click Remove. e. After you remove all duplicate cable modems, click Close, and then restart your computer.
2.	If your cable modem is redetected every time you start your computer, the modem's software may be unable to communicate with the modem during the boot process. To resolve this issue, uninstall the modem driver and then install the latest driver for your cable modem. For information about how to obtain and install the latest driver for your cable modem, contact your cable company's ISP support group or your modem's manufacturer.
3.	If you are unable to connect to the Internet at all, contact your cable company's ISP support group to verify that the proxy server address, Domain Name Service (DNS) address, line-in frequency, and line-out phone number are correct. If you are having performance problems while connected to the Internet, contact your cable company's ISP support group to verify that the connection parameters are in an acceptable range. Some cable modems include a utility that automatically obtains the correct cable connection parameters. If your modem does not include a utility such as this, you can usually obtain connection parameters from your cable company's ISP support group.
4.	If you have more than one network adapter on your multihomed Windows XP-based computer that is using Transport Control Protocol/Internet Protocol (TCP/IP) address from the Automatic Private IP Addressing (APIPA) subnet range 169.254.0.0-169.254.255.255, subnet mask 255.255.0.0, routing to this subnet may not work. For additional information about this issue, click the following article number to view the article in the Microsoft Knowledge Base: 244268 (http://support.microsoft.com/kb/244268/) Routing does not work when multiple adapters use automatic private IP addressing simultaneously

NOTE: Some cable modems can be reset by unplugging and powering down the modem for 10 seconds and then powering the modem back up again.

Back to the top