pologize. My purpose for the last year has been the completion of this book. All other respon- sibilities, with the exception of health and family, took a back seat to my goal. Realizing this book's publication is a dream come true for me. You may have dreams yourself, for which I can offer only this one bit of advice: work toward your goals, and you will realize them. It really is that simple. Preface PART I Hubs, Switches, and Switching This section begins with a brief introduction to networks. It then moves on to describe the benefits and drawbacks of hubs and switches in Ethernet networks. Finally, many of the protocols commonly used in a switched environment are covered. This section is composed of the following chapters: Chapter 1, What Is a Network? Chapter 2, Hubs and Switches Chapter 3, Auto-Negotiation Chapter 4, VLANs Chapter 5, Trunking Chapter 6, VLAN Trunking Protocol Chapter 7, EtherChannel Chapter 8, Spanning Tree CHAPTER 1 What Is a Network? Before we get started, I would like to define some terms and set some ground rules. For the purposes of this book (and your professional life, I hope), a computer net- work can be defined as "two or more computers connected by some means through which they are capable of sharing information." Don't bother looking for that in an RFC because I just made it up, but it suits our needs just fine. There are many types of networks: Local Area Networks (LANs), Wide Area Net- works (WANs), Metropolitan Area Networks (MANs), Campus Area Networks (CANs), Ethernet networks, Token Ring networks, Fiber Distributed Data Interface (FDDI) networks, Asynchronous Transfer Mode (ATM) networks, frame-relay networks, T1 networks, DS3 networks, bridged networks, routed networks, and point-to-point networks, to name a few. If you're old enough to remember the pro- gram Laplink, which allowed you to copy files from one computer to another over a special parallel port cable, you can consider that connection a network as well. It wasn't very scalable (only two computers), or very fast,