Takes one IP address and translates it into another. IT preserves the limited amount of available IPv4 space and sets security safeguards.
A technology that allows a gateway, usually a router or firewall, to rewrite the source IP of an outgoing IP datagram while retaining the original IP in order to rewrite into the response.
Network A - 10.1.1.0/24
Network B - 192.168.1.0/24
NAT - 10.1.1.1 and 192.168.1.1
Computer 1 - 10.1.1.100
Computer 2 192.168.1.100
Destination IP: 192.168.1.100
Source IP: 10.1.1.100
sent to Router
After reaching the Router
Destination IP: 192.168.1.100
Source IP: 192.168.1.1
The source IP address have changed to the router’s IP on Network B or 192.168.1.1. Now, Computer 2 crafts its response and sends it back to router. The router, knowing that this traffic is actually intended for computer 1 , rewrites the destination IP field before forwarding it along. What NAt is doing in this example is hiding the IP of Computer 1 from Computer. This is know as IP masquerading. Ip masquerading is an important security concept. The most basic concept at play here is that no one can establish a connection to your computer if they don’t know what IP address it has. By using NAT in the way we’ve just describe. We could actually have hundreds of computers on Network A, all of their IPs being translated by the router to its own. To the outside world, the entire address space of Network A is protected and invisible. This is known as one-to-many NAT, and you’ll see it in use on lots of LANs today.