What you need for this book
For this book you'll need a copy of Linux, preferably Ubuntu 14.04.
You'll also want access to three computers to install Linux on. One of the servers will need to have three network cards built into it.
For this purpose, I would strongly recommend using Virtual machines (VMs). Virtual Box will allow you to do this for free and is available on Windows, Linux, or OS X. You may find that the commercial offerings from VMWare, Parallels, or Microsoft may provide better performance, however.