Appendix B: Ping and TCP/IP Debugging Tools
#2: You are having a problem with one of your workstations communicating to a server. You know the server's IP address is 192.168.1.100. I enter “ping 192.168.1.100”on the workstation’s command line. If the server is connected, you will receive a response to your ping.
NOTE: It’s easy to find a computer’s IP address. Go to the target computer (the one you wish to ping) and on its command line enter “ipconfig.” The IP address (and other addresses) will be displayed. More information on the ipconfig command can be found later in this section.
The Ping program has endless uses. Ping an address (as above): If you get a response using the IP address but do not get a response using the DNS address, there must be a problem with the DNS system. If you suspect this, try another debugging pro- gram “nslookup.” On the command line, enter nslookup fol- lowed by the DNS name (enter nslookup www. blackbox.com) and see if the IP address is displayed. If it is, your DNS appears to be working correctly. Ping yourself: You can use the ping com- mand to ping yourself, either using your own IP address or what is known as the loopback address. The loopback address is a special reserved address that works on all systems:127.0.0.1 (enter ping 127.0.0.1). If you would like to try pinging your own workstation address but do not know it use the “ipconfig” command (in the next section). Pinging yourself is the first test that should be conducted because if it fails, it most likely means that TCP/IP is not properly loaded on the workstation. If it passes and you were using your own IP address (not the loopback address), it confirms that you are the only one on the network with that address. Ping your gateway: If you get a response, it means that the packets are making it to the router (a gateway is a device on a network that serves as an entrance to another net- work). On business LANs, the gateway is generally the router. In homes, the gateway is the Internet service provider (ISP) that connects the user to the Internet.