What is NAT?

In the field of computer networks, network address translation (abbreviated to NAT) is a mechanism that allows the IP address of transiting packets to be changed through network devices - such as routers or firewalls - during an ongoing communication between two or more network nodes. The NAT mechanism has become crucial since IP addresses of the IPv4 protocol have become scarce. The exponential increase in the number of devices connected to the Internet has meant that the addresses available in this network space (about 4 billion and 300 million) have been quickly used up. NAT has therefore been used to hide dozens and dozens of private addresses (and therefore just as many devices) behind a single public address. Despite the introduction of the IPv6 protocol, this tactic of "masking" private addresses is widely used both for convenience and because it provides a number of advantages. NAT uses a gateway with at least one interface connected to the internal network and at least one network interface connected to the web (and therefore outside the LAN). Thanks to this "portal", all devices connected to the LAN can access the Internet using, and therefore "consuming", a single public IP address, namely the gateway’s. In this case, the gateway takes care of transferring - or translating - the IP addresses of the packets transiting through the router: when an internal network terminal makes a request to the Internet, the resulting source IP address will be the gateway's public IP address and not the private one of the requesting device; in the case of incoming packets, on the other hand, the gateway takes care of redirecting the traffic to the destination devices belonging to the network by modifying the destination IP accordingly.