What is NAT (Network Address Translation)?

NAT allows multiple devices on a private network to share a single public IP address. It's the reason your home router can connect dozens of devices to the internet using just one IP from your ISP.

Why NAT Exists

IPv4 has roughly 4.3 billion addresses — not enough for every device on Earth. NAT was invented in the 1990s as a stopgap, allowing private IP ranges (10.x.x.x, 192.168.x.x, 172.16-31.x.x) to be reused across millions of networks.

Types of NAT

PAT (Port Address Translation)

The most common type. Maps multiple private IPs to a single public IP using different port numbers. Also called "NAT overload." This is what your home router does.

Static NAT

One-to-one mapping between a private and public IP. Used for servers that need a consistent public address.

DNAT (Destination NAT)

Redirects incoming traffic to a different internal address. Used for port forwarding — e.g., sending port 80 traffic to your web server at 192.168.1.100.

NAT and IPv6

IPv6 provides enough addresses (3.4×10³⁸) for every device to have a unique public IP, theoretically eliminating the need for NAT. However, NAT66 exists for organizations that still want the security benefits of address hiding.

NAT Issues

• Peer-to-peer: NAT complicates direct connections (gaming, VoIP, torrents) — hence "NAT traversal" techniques like STUN/TURN
• End-to-end principle: NAT breaks the original internet design where every device is directly addressable
• Performance: NAT tables consume router memory and add slight latency