What Is NAT?

Learn how NAT lets devices share public IPv4 addresses, how port mappings work, and how NAT differs from a firewall.

Network Address Translation, or NAT, changes address information as traffic moves between networks. Home routers commonly use NAT so many private IPv4 devices can share one public IPv4 address.

NAT is central to modern IPv4 networking, but it is often confused with security. It changes and tracks connections; a firewall separately decides which traffic is allowed.

Outbound connection tracking

When a local device opens a connection, the router creates a translation entry that maps the private address and port to a public address and port. Replies use that state to return to the correct device.

Port forwarding

A port-forward rule creates a predictable inbound mapping from the router public address to a specific device and port inside the network.

NAT and firewalls

NAT can make unsolicited inbound connections less straightforward, but it is not a replacement for firewall rules, secure services, updates, and strong authentication.

NAT with IPv6

IPv6 generally does not require address sharing for conservation. Networks still use stateful firewalls, and some environments use forms of translation for operational reasons.

Frequently Asked Questions

Does NAT hide my public IP?

No. Websites see the public address used by the NAT gateway.

Is NAT a firewall?

No. They are often combined in one router, but they perform different functions.

Why is port forwarding needed?

It tells the router where to send selected inbound traffic that would not match an existing outbound connection.