Windows Powershell: nslookup command (same command in OSX)


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When I walk through the steps that a computer takes to resolve an IP address (checking local cache, etc)… I had the kids open up a Windows Powershell command prompt and use the ‘nslookup’ command. I highlight the difference between just running an nslookup command to get an IP address (e.g. “nslookup code.org.”) versus using nslookup to get the IP address of the authoritative nameserver (e.g. “nslookup -q=ns code.org.”). I then have the students re-execute the nslookup command to use the authoritative nameserver (e.g. nslookup code.org. ns-1497.awsdns-59.org.).

It is a nice way to get the kids engaged and break up the teacher air time. I suggest that they perform lookups on various domain names and pick students at random to share results. In each section, a student discovered a domain name that returns more than one IP address for the same domain name, which is a fun discussion to have (see https://en.wikipedia.org/wiki/Round-robin_DNS).

If you also use Windows Powershell to have students run ‘tracert’ in the Lesson 10 (Routers) class, this is another tool to add to their toolkit.

Unfortunately, our district prohibits execution of Windows Powershell scripts, so I have the students run a few whois queries using http://whois.icann.org/ (instead of the whois powershell script you can download and install from Microsoft) and then we talk a little bit about domain registration and registrars.

Windows Powershell whois script