Once TCP/IP is installed and configured on the computers on your network, a variety of helpful and interesting diagnostic and troubleshooting utilities become available to you. Most of these utilities are meant to be run from the command line, so make sure that you have that command prompt icon nice and handy on your desktop. The list below outlines some of the common utilities that you’ll want to be familiar with, along with their primary functions, and examples of how they are used.
PING – The most basic and essential of the TCP/IP utilities, the PING command is used to test basic connectivity on a TCP/IP network. When you ping another host on your network, the machine from which the command is used sends out an “echo request” message, and then determines success by whether it receives back an “echo reply”. When echo reply messages are received, it means that the two computers are capable of communicating via TCP/IP. PING is the first utility that should always be used when attempting to troubleshoot a connectivity issue on a TCP/IP network. The ping command can be used with IP addresses or FQDNs. For example, to ping the PC Answers web server, you would type ping www.pcanwers.co.uk, press Enter. If you receive 4 echo reply messages, you’re likely up and running correctly.
IPCONFIG – The IPCONFIG command represents the easiest way to gather TCP/IP configuration information for your computer from the command line. Instead of accessing your network properties through the Windows interface, simply type ipconfig at the command prompt and press Enter. You will be provided with information on the IP address, subnet mask, and default gateway values configured on your PC. For more comprehensive information (including the IP addresses of DNS servers), type ipconfig /all and press Enter. If you’re running Windows 2000 or XP, try using the ipconfig /displaydns command to view the FQDNs that your system has resolved to IP addresses.
TRACERT – One exceptionally interesting TCP/IP command used to troubleshoot network connectivity issues is TRACERT. The purpose of the TRACERT command is to trace the route that a packet takes between a source and destination host. For example, when you cannot ping a host, it does not necessarily mean that the host is unavailable. Instead, it might mean that a problem exists somewhere on the path between the two hosts. When the TRACERT command is issued with an IP address or FQDN, it will report back with information on the entire path taken (namely the routers crossed) in trying to reach the destination network. For example, try typing tracert www.yahoo.com and press Enter. This command will display all of the routers crossed between your PC and the Yahoo web server, as shown above – probably more than you would have thought!
NETSTAT – The NETSTAT command is useful when attempting to determine the status of connections between your computer and other computers on your network or the Internet. From the command line, type netstat and press Enter. The results will show you both the systems that this computer is connected to, along with the status of the connections.
Traceroute.bmp: Use the TRACERT utility to determine the path that a packet takes between a course and destination host.