What is network address translation?
Network address translation (NAT) changes IP addresses and sometimes port information as packets cross a gateway.
How it works and where it is used
Home routers let multiple private IPv4 devices share one public address. Return traffic is mapped using connection state. This eases IPv4 scarcity, but inbound connections, some games and peer-to-peer applications may need additional setup.
Limits, safety and selection criteria
NAT is not itself a firewall or encryption; apply security policy separately. Carrier-grade NAT may prevent inbound port forwarding from a home router. IPv6 uses a different address model and does not require NAT by default. A home device may use a private 192.168 address that cannot route directly across the public internet. The router records a temporary mapping from outbound traffic to a public address and port, then uses it for replies. Hosting a service reachable from outside may need port forwarding, IPv6 or a tunnel. Shared public addresses also make an IP a poor identifier of a single individual. When debugging, distinguish the device’s local address, the router’s public address and possible carrier-grade NAT.