Network Security First-Step, Second Edition

Network Address Translation (NAT)

The Internet has grown larger than anyone ever imagined. Although its exact size is unknown, the current estimate is that there are approximately 100 million hosts and more than 350 million users actively on the Internet. This is more than the entire population of the United States. The Internet is effectively doubling in size each year.

When IPv4 addressing first appeared, everyone thought there were plenty of addresses to cover any need. Theoretically, you could have 4,294,967,296 unique public addresses (232). The actual number of available public addresses is smaller (somewhere between 3.2 and 3.3 billion) because of the way the addresses have been separated by the Internet Engineering Task Force (IETF) into ...