Explain the Basic Operation of NAT

NAT was originally designed to slow the depletion of available IP address space by allowing many private IP addresses to be represented by some smaller number of public IP addresses. In this regard, its original intent was similar to Classless Inter-Domain Routing (CIDR).

Since then, NAT has also become a useful tool for network migrations and mergers, server load sharing, and creating “virtual servers.” So, in this section, I’m going to describe the basics of NAT functionality and the terminology common to NAT.

Here’s a list of situations when it’s best to have NAT on your side:

• You need to connect to the Internet and your hosts don’t have globally unique IP addresses
• You change to a new ISP that requires you to renumber your network