Ping Lookback Address to test TCP/IP when having Network Connectivity Problems

When you are having network connectivity issues and you have ruled out problems with physical connections such as with your cables and network adapters, or your Windows Troubleshooter in the Windows Help and Support Center pointed to a TCP/IP address problem, you can use the Ping command. TCP/IP  is a network protocol used in the Windows environment.  TCP/IP automatically installs itself when it detects a network adapter.  The Ping command allows you to check for connectivity between devices on your network.

You should Ping the loopback address first.  The loopback address is 127.0.0.1.  IP addresses that have 127 in the first octet are called loopback addresses.  If this check fails, the TCP/IP configuration for your computer is incorrect.  To ping the loopback address:

1. Go to the Start menu.  Point to All Programs/Accessories/select Command Prompt.  Another method is to go to the Start menu, select Run, and type cmd in the selection box.
2. Type ping 127.0.0.1 at the command prompt.  If pinging the loopback address fails, check the TCP/IP configuration.
3. Open Network Connections.  Go to Start/Control Panel/Network Connections.  Right-click on the connection, and choose Properties.
4. Select Internet Protocol (TCP/IP), and click Properties.  Review your configuration.  Do you need a static IP address?  If so, select Use The Following IP Address and enter the address, subnet mask, and gateway to use.  Most home users will need to select Obtain An IP Address Automatically.  If your configuration is correct, you might have to reset TCP/IP.  For instructions on how to reset TCP/IP, see article http://support.microsoft.com/kb/299357
5. Click OK and reboot the computer if prompted.

For further information on TCP/IP troubleshooting tools, see http://support.microsoft.com/kb/314067