This study guide is the result of several years of experience in teaching computer networking and working with networking technologies. Throughout these years, I have remained convinced that learning, understanding, and mastering IPv4 and IPv6 addressing are essential for students pursuing studies in computer networking and for networking professionals seeking to strengthen their knowledge and practical skills in network design and implementation. A thorough understanding of IPv4 and IPv6 addressing provides a solid foundation for the effective design, deployment, administration, and troubleshooting of networks. It facilitates the planning and implementation of new networks and supports the efficient improvement, expansion, and management of existing ones. This study guide is organized into four chapters: 1. IPv4 Addressing 2. IPv4 Subnetting 3. Variable-Length Subnet Masking (VLSM) and Classless Inter-Domain Routing (CIDR) 4. IPv6 Addressing Each chapter presents detailed explanations, practical techniques, and worked examples related to its subject. A series of exercises is also provided at the end of each chapter, with answers included in the appendix. A review of networking textbooks, study guides, and specialized technical documents revealed that IPv4 and IPv6 addressing is often covered too briefly. In many publications, addressing concepts are presented only in summarized form, requiring readers to consult several sources to obtain the depth of knowledge and practical guidance they need. The purpose of this study guide is therefore to bring together, in a single comprehensive and accessible resource, the essential concepts, methods, and techniques associated with IPv4 and IPv6 addressing. Through its detailed explanations, worked examples, and end-of-chapter exercises, the guide aims to help readers develop both a sound theoretical understanding and the practical skills required to apply IP addressing effectively in real-world networks.