CCNA Routing and Switching Practice and Study Guide: Exercises, Activities, and Scenarios to Prepare for the ICND2 (200-101) Certification Exam

Chapter 14. Network Address Translation for IPv4

All public IPv4 addresses that transverse the Internet must be registered with a Regional Internet Registry (RIR). Only the registered holder of a public Internet address can assign that address to a network device. With the proliferation of personal computing and the advent of the World Wide Web, it soon became obvious that 4.3 billion IPv4 addresses would not be enough. The long-term solution was to eventually be IPv6. But for the short term, several solutions were implemented by the IETF, including Network Address Translation (NAT) and RFC 1918 private IPv4 addresses.

NAT Operation

There are not enough public IPv4 addresses to assign a unique address to each device connected to the Internet. ...