Automating System Administration with Perl, 2nd Edition

Chapter 13. Network Mapping and Monitoring

People who administer networks of machines, even if they don’t officially have the title “network administrator,” care about the answers to at least two basic questions: “What’s on my network?” (mapping) and “Are the nodes doing what I think they should be doing?” (monitoring). Even though you’d probably like to think the first question is an easy one (after all, it is your network, right?), the answer turns out to be less simple in these days of $20 mini-hubs and wireless access. Making sure that the web servers are constantly serving HTTP or HTTPS, the routers are moving packets, and the database servers can be queried has become really important. Perhaps even more important is knowing when the web servers suddenly start serving SMTP, the database servers unexpectedly begin offering web access, or the routers are dropping packets. This chapter is about answering both the mapping and monitoring questions. Its goal is to help you identify and understand the various components necessary to build the custom solutions you need in these areas.

Network Mapping

We’ll start by looking at the mapping question, because it’s generally a good idea to know exactly what you have before you start trying to monitor it. Back in the Mesozoic age of computing, it was much easier to map one’s environment. The most sophisticated tools you needed were a pencil and paper and a few moments of quiet reflection. There were fewer computers, all ran services you’d ...