Network Commands

For any computer connected to the internet, at some point, the internet connection will not work. This can be extremely frustrating, especially if the internet connection is supplied by a low cost ISP who has cut costs by not providing technical support of any worth.

It may be that in this situation, the only way to contact the ISP is via:

  • The phone (of course, the phone number will be on the ISP’s website, and since the internet connection is not working, they can’t be phoned up)
  • Email (of course, the email address will also be on the ISP’s website, and since the internet connection is not working, they can’t be emailed)
  • Web form (of course, the web form is on the ISP’s website, and since the internet connection is not working, they can’t be contacted via the web form either)

It is at times like this, that it becomes painfully apparent why a good ISP is worth paying for, and making a note of relevant numbers on paper is a good back up option.

However, even given these problems, all is not lost, since it is possible to use a core set of network commands / software tools that are essential for troubleshooting and diagnosis. This way, it is possible to isolate the problem before even contacting the technical support line. These network commands / software tools are available on Linux and UNIX operating systems, and some of them are available on Windows operating systems, so they are pretty widely spread. This core set of tools are the following:

  • ping
  • netstat
  • traceroute / tracert
  • nslookup

 

Diagnosis.

To diagnose any problems with an internet connection. There are a number of straight forward steps to take before anything else:

  1. First of all, one needs to check that the internet connection really is down. To do this, in Linux or UNIX, open a terminal window. In Windows, press start, then choose the run option, then type cmd in the run box to get a command prompt (a window with a black background).
  2. Type ping www.domainname.com where domain name is a website domain known to exist, or even better, if an IP address other than the local machine’s IP address is known, then type ping xxx.xxx.xxx.xxx where the xxx is the known IP address.
  3. If step 2 did not work, then the next test to try is to ping the web server of the ISP. Again, following the same procedure as above, one would type ping www.ISPdomainname.com or the IP address of the ISP. If this works, then the ISP is OK, but their link to the internet may well be having problems.
  4. If step 3 did not work, then the next test to try is to ping the current local machine. Once again, following the same procedure as above, one would type ping xxx.xxx.xxx.xxx (the IP address of the current local machine). If this works, then the current local machine is OK, but there may be a routing problem.
  5. If step 4 did not work, then the next test attempts to determine whether the physical attributes of the network adaptor hardware in the machine are OK. It may be that the hardware is faulty, damaged or has just overheated.