NAT (Network Address Translation)

A method of remapping IP addresses by modifying network address information in packet headers, allowing multiple devices to share a single public IP.

What is NAT?

Network Address Translation (NAT) is a technique used to modify IP address information in packet headers as they pass through a router or firewall. NAT enables multiple devices on a private network to access the internet using a single public IP address.

How NAT Works

When a device on a private network sends traffic to the internet, the NAT device replaces the source IP address with its own public IP address. It maintains a translation table to track connections, ensuring responses return to the correct internal device.

Types of NAT

Static NAT: One-to-one mapping between private and public addresses
Dynamic NAT: Maps private addresses to a pool of public addresses
PAT (Port Address Translation): Multiple devices share one public IP using different ports
NAT64: Translates between IPv6 and IPv4 addresses

Benefits and Limitations

Benefits:

Conserves IPv4 address space
Provides basic security by hiding internal addresses
Enables flexible network design

Limitations:

Can break end-to-end connectivity
Complicates peer-to-peer applications
May impact certain protocols requiring consistent addressing