This book is about wireless local area networks (WLANs) based upon the IEEE 802.11 standards. It has three primary objectives: * To introduce the principles of 802.11 wireless networks and show how to con- ure equipment in order to implement various network solutions. * To provide an understandingof the security implicationsof wireless networks and demonstrate how vulnerabilities can be mitigated. * To introduce the underlying 802.11 protocols and build mathematical models in order to analyse performance in a WLAN environment. The book is aimed at industry professionals as well as undergraduate and gra- ate level students. It is intended as a companion for a university course on wireless networking. A practical approach is adopted in this book; examples are provided throughout, supported by detailed instructions. We cover a number of wireless vendors; namely, Cisco's Aironet, Alactel-Lucent's Omniaccess and Meru Networks. While separate vendors, all three systems have a Cisco IOS-like command-line interface. The GNU/Linux operating system is used extensively throughout this book.