IPv4 exhaustion refers to the depletion of available IPv4 addresses for connected devices. The original pool of IPv4 addresses numbered less than 4.3 billion, and the depletion has been anticipated since the late 1980s due to the rapid growth of the Internet.
This exhaustion has led to the development and deployment of its successor protocol, IPv6. To mitigate IPv4 exhaustion, various technologies have been implemented, including IPv4 address sharing, IPv6 dual-stack implementation, protocol translation, and bridging and tunneling. Regional Internet Registries (RIRs) have also set aside small pools of IP addresses for the transition to IPv6.
The exhaustion of IPv4 addresses has led to the adoption of technologies such as Classless Inter-Domain Routing (CIDR), Network Address Translation (NAT), Carrier-Grade NAT (CGNAT), and the IPv4 transfer market. While IPv6 is considered the long-term solution to the issues derived from IPv4 depletion, its adoption is still taking place at a slow pace.