With the tremendous increase in the use of internet in almost every sector of society, assigning addresses has appeared to be inefficient. The previous Internet Protocol version 4 (i.e. IPv4) failed to fulfill the highly growing demand. Though previous Internet Protocol Version 4 was used for assigning addresses, it could not sustain the high demand resulting in the downfall of IPv4. The chapter outlines the various advantages and disadvantages of the shift from IPv4 to IPv6. It also highlights the security threats of both the protocols and security issues due to which the coexistence of the two protocols was thought of as the solution. This chapter overall covers the transition from IPv4 to IPv6, their uses and management, followed by the analysis of IPv6 in terms of security issues. It further takes into account the effect of IPv6 on the world of Internet of Things (IoT). The eventual objective of this framework is to give comprehensive and detailed knowledge about the internet protocols in the Internet-of-Things world.