One of the most common reasons for a service call for a computer is because a user can't get "the Interne", or their email, or some other network resource. Finding the problem requires a set of tools that will help you locate what's available on the network. From there it's a matter of deducing where the problem lies, and if it lies on your network at all.

The following is list of command line tools that are useful for troubleshooting networking problems from a Windows computer. There are similar, and often more powerful tools available in Linux, but the tools to discover these are built in to Linux systems (apropos and man). It helps to have a list of useful network tools for Windows systems.

Each of these tools has help with usage and syntax, and that help is available from the command line by following the command with the /? switch. You get to the command line (dos box) on an XP system by clicking [Start] -> Run and putting cmd in the field before hitting the Enter key. On a Vista system, getting a command line is not that obvious. On Vista, type cmd into the search field and hit Enter. Go figure!

ipconfig

This command will tell you the local machine's ip address, and the gateway machine. the /renew switch will cause the interface to try to get a new ip lease from the DHCP server.

net view

The net command has quite a few options. The view option lists the names of computers on the network.

The start and stop options of the net command are frequently used with the spooler to start and stop the printer service.

The share option makes a resource available to other computers through the server message block protocol, and the use command is useful in logon scripts to map network drives, especially on domains.

arp -a

The arp command, although of limited use, can help discover ip addresses.

netstat -a

 This command lists ports that are open and listening for connections. This can be very useful in certain circumstances.

nbtstat -c

This is useful for discovering computer names and their associated ip and mac addresses. Also look at the -a switch.

nslookup

This command, followed by a domain name, will try to return the ip address of that domain name.

ping

This is useful for checking connections and how far the network packets can travel. You can use either domain names or ip addresses with this command. Sometimes you can isolate a problem to a particular device if you can get a response from pinging it's lan side address, but none from it's wan side address.

tracert

This is similar to ping, but gives a list of all connections made en route to the destination name or ip address. It also lists time taken, so you might be able to gain some insight into where slowdowns and bottlenecks might be.