WAN Technologies CCNA 4 Companion Guide is the official supplemental textbook for the CCNA 4 course of the Cisco Networking Academy Program. Completely revised from the previous edition with new examples and explanations, this textbook includes original material developed by the author, yet it fully aligns with the CCNA 4 curriculum. Written by an experienced author who present material in a comprehensive manner--using his own voice and own examples--this new edition augments student understanding of course material. The new edition incorporates improved features to aid instructors and enhance student comprehension. For example, chapters align with course modules in both name and number, and chapter objectives are stated as questions to encourage students to think about and find answers as they read chapters. End-of-chapter questions and summaries align with chapter objectives to emphasize key topics, while key terms are listed in each chapter opener in the order of occurrence to alert students to upcoming vocabulary words. In addition, new features include "How To" quick references for step-by-step tasks; real-world examples and all-new illustrations; concise explanations with a focus on word usage and sentence structure for improved readability; and correlations to the CCNA exam in Chapter Objectives, Check Your Understanding questions, and new Challenge Activities.