This book explores the essential concepts and practical implementation of IPv6, the next-generation Internet Protocol designed to address the limitations of IPv4 and support the exponential growth of Internet-connected devices. IPv6 Fundamentals: Packet and Data Structures, Addressing Architecture, Device Discovery, and Configuration Protocols delivers critical knowledge through detailed explanations of IPv6 header and extension formats, addressing architecture, neighbor discovery protocols, and DHCPv6 operations. Readers benefit from comprehensive coverage of mobility mechanisms that enable seamless roaming across networks, along with practical implementation guidance for transitioning from IPv4. This book uniquely bridges theoretical concepts with real-world applications, explaining not just how IPv6 functions work individually, but how they interconnect within the broader network ecosystem between hosts and routers. The author specifically focuses on the technical foundations of IPv6 packet structures and neighbor discovery protocols at a deeper level than existing titles. Finally, this book includes appendices covering Ethernet frame formats, IPv4 packet structures, and various ARP mechanisms, providing valuable context for understanding the evolution from IPv4 to IPv6. This book is intended for network engineers, IT administrators, system architects, and telecommunications professionals responsible for planning, implementing, and managing network infrastructure. Academic readers, including advanced undergraduate and graduate students in computer networking courses, will appreciate the clear explanations of fundamental concepts.