How to troubleshoot possible causes of Internet connection problems in Windows XP

This article describes ways to diagnose and resolve issues that can cause problems when you try to use one of the following to communicate with servers on the Internet:

• Internet browser
• File Transfer Protocol (FTP)
• Telnet

This article assumes that you can successfully connect with and log on to your Internet service provider (ISP).

Any one of the following issues can cause problems when you try to communicate with a server on the Internet:

• The server is not functioning correctly or has been temporarily removed from the Internet.
• Your Internet browser is not configured correctly.
• The TCP/IP configuration for your dial-up connection to your ISP is incorrect.
• Your ISP's Domain Name Service (DNS) server is not working correctly.
• Hosts files in the System_drive:\Windows, System_drive:\Windows\System32\Drivers, and System_drive:\Program Files\Network Ice\Black Ice directories may be damaged or corrupted.
  
  Note System_drive is a placeholder for the drive where Windows is installed,

To determine the cause and resolution of the problem that you are experiencing, follow the procedures in each of the following sections, in the order that they are presented in. After you complete a procedure, try again to see whether you can successfully communicate with servers on the Internet.

Try a known good server

If you cannot communicate with a specific server on the Internet, try to connect to the Microsoft Web site by using its fully qualified domain name (FQDN): An FQDN is made up of a host name (in this case, "microsoft") and a domain name (".com"). If you can connect to the Microsoft Web site by using its FQDN, the TCP/IP configuration on your computer is correct.

If you can connect to the Microsoft Web site but you cannot connect to another specific Internet site after several tries, the other site may not be functioning correctly or may be temporarily removed from the Internet. Try to connect to some different Web sites. If you can connect to some Web sites but not to other Web sites, contact your ISP if you need help.

If you cannot connect to any Web sites, there may be an issue with your Internet browser configuration or with the TCP/IP configuration for your dial-up connection to your ISP.

Make sure that your browser configuration is correct

Make sure that your Internet browser (for example, Microsoft Internet Explorer) is correctly configured to connect to the Internet through the dial-up connection to your ISP, and make sure that your Internet browser is not configured to connect through a proxy server. (A proxy server is a computer or a program that acts as a "go-between" barrier between a local area network (LAN) and the Internet. A proxy server is a firewall component that presents one single network address to external sites.)

To verify these settings, start Internet Explorer, and then click Internet Options on the Tools menu. Click the Connections tab, and then view the settings that relate to your ISP.

To see whether your browser is using a proxy server, click LAN Settings.

Confirm your Internet Protocol (IP) address

If your ISP has given you a static (permanent) IP address, make sure that the TCP/IP configuration for your ISP connection contains the correct information. Follow these steps:

1. Connect to your ISP.
2. Start a command prompt, type the following command, and then press ENTER:
   ipconfig /all
   The ipconfig /all command displays Windows TCP/IP settings for all your network adapters and modem connections. The address for a modem connection is displayed as "NDISWAN x adapter", where x is a number. The default gateway for the NDISWAN x adapter is the same as the IP address. This is by design. More than one NDISWAN x adapter may be displayed. Any NDISWAN x adapters that are not currently in use display zeros for the IP address.
3. If the IP address that is displayed for your dial-up connection to your ISP does not match the IP address that your ISP gave you, change the IP address that is displayed so that it matches the address that your ISP gave you. Follow these steps:
   1. Click Start, point to Settings, click Control Panel, and then double-click Network Connections.
   2. Right-click your Internet connection, click Properties, and then click the Networking tab.
   3. Click the Internet Protocol adapter, and then click Properties.
   4. If the settings are not correct, change the TCP/IP settings to match the settings provided by your ISP, click OK, and then click OK again.

Turn on the option to use a default gateway on the remote network

If you connect to a local network by using a network adapter and, at the same time, connect to your ISP by using a modem, configure your dial-up connection so that any routing conflicts are resolved in favor of your dial-up connection to your ISP. Follow these steps:

1. In Control Panel, double-click Network Connections.
2. Right-click your Internet connection, click Properties, and then click the Networking tab.
3. Click the Internet Protocol adapter, click Properties, and then click Advanced.
4. Click to select the Use default gateway on remote network check box, and then click OK.
5. Click OK.

Check the transfer and receive lights

If you connect to a local network by using a network adapter and, at the same time, connect to your ISP by using a modem, a conflict between your network adapter and your modem can prevent your modem from sending information to servers on the Internet. To verify that TCP/IP packets are being routed through your modem to your ISP, follow these steps:

1. Connect to and log on to your ISP.
2. Use the ping command to cause your modem to send test information. At a command prompt, type the following command, and then press ENTER:
   ping IP address
   
   where IP address is the IP address of a known good server on the Internet. If you do not know the IP address of a server on the Internet, use the IP address for ftp.microsoft.com, 207.46.133.140.

Dial-Up Networking Monitor uses lights to show the modem status.

• If the transfer (Tx) light in Dial-Up Networking Monitor flashes when you ping a server on the Internet, TCP/IP information is being routed through your modem to your ISP.
• If the transfer (Tx) light in Dial-Up Networking Monitor does not flash when you ping a server on the Internet, packets are not being routed through your modem. Make sure that the IP address that your ISP assigned to you for your dial-up connection is different from the IP address for your network adapter or loopback driver (if one is installed). Also, the IP address of your network adapter or loopback driver must not be on the same network as the IP address that your ISP assigned for your dial-up connection.
• If the receive (Rx) light in Dial-Up Networking Monitor does not flash when you ping a server on the Internet, packets are not being received from your ISP. Contact your ISP if you need help.
• If the receive (Rx) light in Dial-Up Networking Monitor flashes when you ping a server on the Internet, but you still cannot connect to the server by using its FQDN, there may be a name resolution issue.

Test the name resolution

A DNS server provides host name resolution. If you cannot connect to a server on the Internet by using its FQDN, there might be an issue with the DNS configuration of your dial-up connection to your ISP or with your ISP's DNS server.

To determine whether there is an issue with the DNS configuration of your dial-up connection to your ISP, follow these steps:

1. At a command prompt, type ipconfig /all, and then press ENTER to display the IP address of your DNS server. If the IP address for your DNS server does not appear, contact your ISP to obtain the IP address for your DNS server.
2. To verify that your computer can communicate with your DNS server, ping your DNS server's IP address. The reply looks something like this:

      Pinging ###.###.###.### with 32 bytes of data:
   
      Reply from ###.###.###.###: bytes=32 time=77ms TTL=28
      Reply from ###.###.###.###: bytes=32 time=80ms TTL=28
      Reply from ###.###.###.###: bytes=32 time=78ms TTL=28
      Reply from ###.###.###.###: bytes=32 time=79ms TTL=28 

   The series of number signs (###.###.###.###) represents the IP address of the DNS server.

If you cannot successfully ping the IP address of the DNS server, contact your ISP to verify that you are using the correct IP address and that the DNS server is working correctly.

If you can ping the IP address of your DNS server but you cannot connect to a server on the Internet by using its FQDN, your DNS server may not be resolving host names correctly. If more than one DNS server is available for your ISP, configure your computer to use a different DNS server. If using another DNS server resolves the issue, contact your ISP to correct the issue with the original DNS server.

Examine the host files

Open Internet Explorer. Connect to the Internet. Type www.microsoft.com and other FQDN addresses in the address bar, and then click Go. MSN Search reports that no page is found. However, if you type the IP address for any one of the Web sites, the Web site appears.

To resolve this issue, follow these steps:

1. Search for hosts files on the local hard disk(s).
2. If file name extensions are visible, find any hosts file without the .sam extension, open it with Notepad to verify that it contains references to the sites that are unavailable.
3. Delete all hosts files that do not have the .sam extension.

When you have verified the correct IP address for your DNS server, update the TCP/IP settings for your dial-up connection to your ISP. To change or add a valid IP address for your DNS server for a Dial-Up Networking phonebook entry, follow these steps:

1. In Control Panel, double-click Network Connections.
2. Right-click your Internet connection, click Properties, and then click the Networking tab.
3. Click the Internet Protocol adapter, and then click Properties.
4. Click Use the following DNS server addresses, and then type the correct IP address in the Preferred DNS Server box.
5. Click OK, and then click OK again.