The Cisco SAFE Implementation Exam (which carries the examination ID number of 642-541) is intended to evaluate whether you understand the ideas behind a secured network architecture and whether you can implement such an architecture (across a wide range of network types) using Cisco Systems' equipment.
That's a tall order. This is not an easy exam.
However, it's not a hurdle too high if you have properly prepared yourself. Understanding the material in this book is one part of that preparation. Understanding basic networking is another: That includes concepts such as the OSI model and what happens at each layer, how IP addressing works and what addresses are used where, and what the various networking devices are and do. All of these ...