Computer Networks

INCOMPLETE: this pracsheet is still being revised

Practical Exercises #8

1. The nslookup and dig Unix command-line utilities allow humans to look up RRs in the DNS. They work in rather different ways, with nslookup being oriented towards an interactive user interface, whilst dig wants all of its arguments on the command line. However, dig can be regarded as better in that it shows all of the RRs returned from the DNS, whereas nslookup only gives you the answer to your question. You can also ask dig to return any RRs associated with a particular domain name. Note that there are software tools with similar functionality for both PCs and Macs.

   Use these utilities to investigate the DNS. Within nslookup, type h for help and take it from there. Try typing bindi.bendigo.latrobe.edu.au and bindi.bendigo.latrobe.edu.au. (ie, with a trailing dot). Try just bindi on its own, and bindi.bendigo Interesting? Try set query=CNAME, or a few other RR types, then repeat the exercise. Try a PTR lookup - how do each of the utilities handle these? What about an SOA? NB: use exit or ^D to quit from nslookup.

2. Investigate some hosts which have
3. Ever thought of registering your own domain name? It's not so difficult. In Australia, check out AUNIC. It has links to just about everything you could want to know about Internet domain names.

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