NAT (Network Address Translation) is a network addressing technology that allows devices from private local networks to access the internet through one or several public IP addresses. A router with NAT replaces internal device IP addresses and ports with its own external address, providing access to external resources and hiding the internal network structure. NAT has become a key mechanism in IPv4 networks due to the shortage of public addresses and is widely used in office, home, and corporate networks.
How NAT works
The router intercepts outgoing traffic from the local network and performs address translation. In the NAT table, it stores mappings between internal addresses and the external IP with specific ports. When a response arrives from the internet, the router uses this table to restore the original route and deliver the packet to the correct client inside the network. As a result, external systems see only one public address, even if dozens or hundreds of devices are operating inside the network.
Main types of NAT
- Static NAT. One internal device is mapped to one public address. Used rarely, typically for servers that require a constant external presence.
- Dynamic NAT. Several internal addresses use a pool of public addresses. Each device is temporarily assigned a free external IP.
- PAT (Port Address Translation). The most common type. Multiple internal devices share one public IP, with differentiation performed through port numbers. Also known as NAT overload.
- NAT64 / DNS64. Mechanisms for interaction between IPv6 and IPv4 networks, allowing IPv6-only devices to access IPv4 resources.
Tasks solved by NAT
The technology addresses several important networking tasks:
- conservation of public IPv4 addresses;
- increased security through hiding internal topology;
- simplified internet access for many devices through a single IP;
- traffic control and filtering at the router level;
- adaptation between IPv4 and IPv6 networks.
NAT is not a full-fledged security tool, but it provides a basic layer of masking, making direct access to internal devices more difficult for external entities.
Where NAT is used
The technology is used almost everywhere: in home routers, office networks, corporate infrastructures, cloud platforms, virtual environments, and container environments.
For example, when connecting a laptop to office Wi-Fi, NAT allows all employees to access the internet through a single external company IP address. In virtual machines and Docker containers, NAT is used to access external resources while maintaining isolation of environments.
Advantages of using NAT
NAT enables network scalability without requiring a large pool of public IP addresses, simplifies infrastructure management, and creates an additional layer of abstraction between internal and external environments. With flexible configuration, NAT supports complex network topologies, tunnels, cloud services, and hybrid architectures, making it a fundamental technology for modern networks.