Network Address Translation (NAT) is a process that enables the mapping of multiple private IP addresses within a local network to a single public IP address before transferring data to the internet. It allows a single, unique IP address to represent an entire group of computers, conserving the number of public IP addresses in use. NAT is typically implemented in routers or NAT firewalls and can be of various types, such as static NAT, dynamic NAT, and port address translation (PAT). Its main purposes are to conserve IP addresses and enhance security by hiding the entire internal network. NAT is an essential tool in conserving global address space in the face of IPv4 address exhaustion.
NAT works by modifying the network address information in the IP header of packets, enabling one public IP address to be used for an entire private network. It translates private internal network addresses into legal, globally unique addresses before forwarding packets between the connected networks. This process effectively hides the entire internal network and provides additional security.
NAT is widely used to enable private IP networks to connect to the internet and cloud, and it allows organizations to connect IPv6 and IPv4 networks using NAT64 translations. Additionally, carrier-grade network address translation (CGN or CGNAT) is used to handle tens of millions of NAT translations, supporting large-scale networks.
In summary, Network Address Translation (NAT) is a crucial process that enables the conservation of public IP addresses and enhances security by allowing multiple devices within a private network to access the internet through a single public IP address.