Of the preparation guides available for the Cisco Certified Design Associate exam (640-441), CCDA: Cisco Certified Design Associate Study Guide comes out on top. Authors Todd Lammle and Donald Porter clearly explain what you need to know, both to pass the exam and to prove yourself a competent network technician once on the job. Some of the material that appears in these pages - a table listing various Cisco router product lines, their capabilities, and suitable applications for them, to cite one example - makes great reading, and will prove useful long after the exam is over.The authors' presentation style uses text to great effect, explaining potentially confusing topics with clear, fact-rich prose that rewards close attention from the reader. There are plenty of helpful conceptual diagrams (illustrating network segmentation with a bridge, for example) and flow charts (a good one illustrates packet-switching logic) as well.It's sometimes possible to forget that this is an exam preparation aid, but realistic problems and multiple-choice review questions bring readers back to the task at hand. Elaborate solutions to the problems and quick answers to the review questions appear in the back of this book (along with an excellent, extensive glossary), but the answer key would be more helpful if it included brief discussions explaining the reasoning behind the correct answers.