According to the Perl web site, "Perl is a high-level programming language with an eclectic heritage written by Larry Wall and a cast of thousands. It derives from the ubiquitous C programming language and, to a lesser extent, from sed, awk, the Unix shell, and at least a dozen other tools and languages. Perl's process, file, and text manipulation facilities make it particularly well-suited for tasks involving quick prototyping, system utilities, software tools, system management tasks, database access, graphical programming, networking, and world wide web programming."
Many of the scripts written in Perl these days tend to involve dynamically generating web pages. But all of the scripts in this book use Perl at the command line of either a Unix or Windows computer.
We frequently use Perl for scripting network administration functions because it is an extremely powerful and flexible language, particularly for things like pattern matching. This makes it perfect for tasks like scanning logfiles, as well as for spawning dynamic queries and formatting the output into a useful report.
Perl is available for both Unix and Windows systems. This is important because while the engineers who run most of the world's larger networks use Unix, smaller organizations frequently don't have any Unix expertise. So it is not uncommon to see Windows computers managing smaller networks.
Perl's free and open distribution policy means that there is usually a good port available, even if you use a different system. And, most importantly for organizations on a tight budget, it's free.
The scripts in this book were written and tested with a variety of different releases of Perl Version 5. However, we deliberately wrote the scripts to be as portable as possible, so they should run without alteration in most versions of the language.
The official Perl web page is http://www.perl.com/. This site has a wealth of information to help people who program in Perl, including many helpful ideas for beginners.
You can download the most recent source code for Perl from the Perl web site. This site also has compiled versions for a variety of platforms. The following URL will direct you to the download area: http://www.perl.com/pub/a/language/info/software.html
The Perl web site also has extensive documentation that is quite well-written and easy to follow at http://www.perl.com/pub/q/documentation.
There are also several excellent books on Perl that you may find helpful. Programming Perl by Larry Wall, Tom Christiansen, and Jon Orwant (O'Reilly) is an excellent to the language and its features. We also recommend Perl in a Nutshell by Ellen Siever, Stephen Spainhour, and Nathan Patwardhan (O'Reilly). And, if you are interested in seeing some of the other things that you can do with this language, have a look at Perl Cookbook by Tom Christiansen and Nathan Torkington (O'Reilly).
Router Configuration and File Management
User Access and Privilege Levels
Handling Queuing and Congestion
Tunnels and VPNs
NTP and Time
Router Interfaces and Media
Simple Network Management Protocol
First Hop Redundancy Protocols
Appendix 1. External Software Packages
Appendix 2. IP Precedence, TOS, and DSCP Classifications