What is Network Address translation used for?

Answer 1

The main use is for an entire network to share a single public IP address - or a small set of public IP addresses. The computers in the network would typically use private addresses, as defined in RFC 1918 - for example, IP addresses that have "10" in the first byte.

Example -

There is a network of 5 computers:

PC1 (192.168.1.1), PC2 (...1.2), PC3 (...1.3), PC4 (...1.4), PC5 (...1.5)

Connected to a router:

ROUTER (216.27.61.137)

Which is connected to the internet:

INTERNET

Which has other computers on it.

PC6 (217.47.63.149) - This computer does not have NAT because there is no router.

1. If PC1 wants to send PC3 some information, it will reference 192.168.1.3 through the router.
2. If PC2 wants to send PC6 something, its IP address (192.168.1.2) is masked by the router, and instead the router's IP is used (216.27.61.137).
3. If PC6 wants to send PC5 anything, PC6 uses its own IP (217.47.63.149), and sends the information to the router (216.27.61.137). It also references PC5 inside that: 192.168.1.5.
4. If a hacker comes along, they try to hack PC 1.They can't, because they don't know where it is in the network (192.168.1.1)!
5. If the hacker tries to hack PC6, he knows where to get it: 217.47.63.149!