The Cisco CCNA certification is considered one of the most valued in the field of networks and communications worldwide. It proves that its holders have the necessary knowledge to perform each of the functions carried out by a network administrator. In addition, it acts as an access requirement for more prestigious certifications, such as the CCNP.This book contains the official Cisco agenda required to obtain the CCNA and, as a result, the reader will acquire the necessary skills to design, manage and secure a medium-sized corporate network, as well as the capacity for analysis and resolution of incidents when necessary.To achieve this purpose, the work is divided into 7 chapters, through which they are analyzed from the most basic concepts, such as TCP / IP and OSI, to advanced protocols. It is a mostly practical approach, where all configuration is applied to Cisco devices.The main objective of this book is to provide its readers with the necessary knowledge to get prepared for the CCNA certification exam. All theory is accompanied by examples and practical configuration assumptions in the required subjects. We recommended you use the “Packet tracer” application, developed by Cisco. If you are interested in advancing your career, get started today!