You need to have a basic networking knowledge to start with this book. You should also have a good understanding with Communication Models, Network Services & Architecture, Media, Devices and Protocol Suites. Understanding TCP/IP classless addressing scheme is essential.
You are expected to have an introductory concept to any of the common UNIX flavored operating systems like: Redhat, Slackware, Suse, Mandrake, BSD group of UNIX, SunOS. Windows administrators are expected to have a clear idea about command line as well.
You need to be content with basic internet facilities. Because, the referred learning materials are available in internet.