The challenge of using IPv4 on the internet

One of the many issues we face is that there aren't enough public IPv4 addresses to assign to each unique device on the internet. As you learned in Chapter 3, IP Addressing and Subnetting, each device that is directly connected to the internet must be assigned a unique IP address. Furthermore, there are 232 public IPv4 addresses, which means that there are approximately 4,294,967,296 public IPv4 addresses that are routable on the internet. This number seems huge, but the reality is that most internet-connected devices have already been assigned a public IPv4 address and the rest of the public IPv4 pool is reserved by various organizations for special use.

In the world today, there are more than 4 billion devices connected to the internet. How is it possible to have more devices online than the number of available public IPv4 addresses? RFC 1918 defines three classes of IPv4 addresses that are assignable on private networks and are...