Useful Tools for Network Troubleshooting
In this section, I'd like to list the tools mentioned previously, and add a few others that I use. At some point, I plan to expand this section with examples for the tools not already used elsewhere. For now, this is just a list of those tools with a short explanation of each. It's a work in progress.
ipconfig - The command used in a command prompt window on Windows-based systems to display the current IP settings of the Ethernet adapters.
netstat - A command used in a command prompt window that will return various sorts of network status and configuration information. It can be used to find out how your computer is routing data and what ports are listening for connections or using outgoing connections.
nslookup - A command used in a command prompt window that queries a domain name server (DNS) with a command network name (e.g., www.google.com) and returns an IP address associated with that name.
ping - The command used in a command prompt window that can be used to send a test message to another device which will reply with the same message.
Ping Plotter - A Windows program available in free, standard and professional versions that does the same thing as tracert and ping, but with a graphical display that makes it easy to see where network slowdowns are occurring. The free version includes a 14-day trial to the other versions. The professional version is pricey, but the standard version is $40. The main differences are the ability to trace two targets at once (e.g., one known to be reliable or close and one that is under test) and keep the trace history for an indefinite period rather than only 10 minutes.
Process Explorer - A Windows program from Microsoft that can ferret out what services are running with every option imaginable. Works on every Windows OS since Windows XP. Windows' Task Manager has a Services tab that provides some of the functions, but not at as fine of level of granularity.
Speed tests - Web sites that will allow you to perform a speed test over the Internet to see if you are getting the speed you are paying for. Good speed tests can be found at www.dslreports.com, www.speedtest.net, myspeed.visualware.com, and www.speakeasy.net.
tracert - A command used in a command prompt window on Windows-based systems to trace the route taken by a packet send from your computer to another computer or device. (Linux/Unix users will recognize this as a version of traceroute - with differences.) The IP addresses of the intermediate nodes are given along with the time it took for the response. The information is the same as that returned by Ping Plotter, but is included with the Windows OS like ipconfig, ping, nslookup, and netstat.
WinIPconfig - A Windows GUI version of the ipconfig command.
Wireshark - (Formerly known as Ethereal) A program for Windows, OS X & Linux that can be configured to capture data traffic based on a set of criteria like source IP address, port number used, etc. Gathers statistics on what it captures.