Types of Network Address Translation
In this section, I’ll go over the three types of NAT with you:
Static NAT
This type of NAT is designed to allow one-to-one mapping between local and
global addresses. Keep in mind that the static version requires you to have one real Internet IP
address for every host on your network.
Dynamic NAT
This version gives you the ability to map an unregistered IP address to a registered
IP address from out of a pool of registered IP addresses. You don’t have to statically
configure your router to map an inside to an outside address as you would using static NAT,
but you do need to have enough real, bona fide IP addresses for everyone who is going to be
sending packets to and receiving them from the Internet.
Overloading
This is the most popular type of NAT configuration. Understand that overloading
really is a form of dynamic NAT that maps multiple unregistered IP addresses to a single
registered IP address—many-to-one—by using different ports. Now, why is this so special? Well,
it’s also known as Port Address Translation (PAT). And by using PAT (NAT Overload), you get
to have thousands of users connect to the Internet using only one real global IP address—pretty
slick, yeah? Seriously, NAT Overload is the real reason we haven’t run out of valid IP address
on the Internet. Really, I’m not joking.