First we look at what exactly NAT is? It means Network Address Translation. This technology or technique was developed to overcome the shortage of public IP addresses in IPv4 standard. With the invent of NAT, the problem of shortage of public IP addresses has been solved quite a bit. Now we have moved to IPv6 which has a lot more addresses than IPv4 but still most of the world uses IPv4 in combination with NAT.

If anyone wants to dig down deep to understand NAT, he can go to the following Wikipedia article:

http://en.wikipedia.org/wiki/Network_address_translation

Now let’s start by configuring a basic NAT on a Cisco router. The type of NAT we are going to configure here is Overloading. This means that we will map one public IP address to many private or local IP addresses.

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