Network Address Translation (NAT)
This is a method that allows multiple devices on a local network to be mapped to a single public IP address, which conserves the number of public IP addresses needed.
How it works
- Private to Public – When a device on a private network sends a packet to the internet, the NAT device (typically a router) changes the private IP address of the sender to the router’s public IP address.
- Public to Private – When a response packet comes back, the NAT devices translates the public IP address back to the private IP address of the original sender, ensuring the packet reaches the correct device on the private network.
Types of NAT
- Static NAT: Maps a single private IP address to a single public IP address. one-to-one mapping.
- Dynamic NAT: Maps a private IP address to a public IP address chosen from a pool of public addresses. It is a many-to-many mapping.
- Overloading (PAT): Uses a single public IP address to map multiple IP addresses by differentiating the connections using port numbers. It is many-to-one mapping.
Port Address Translation (PAT)
This is an extension of NAT that permits multiple devices on a local area network (LAN) to be mapped to a single public IP address, using multiple port numbers to distinguish between the multiple devices.
How it works
- Private to Public – Each device on the private network is assigned a unique port number by the PAT device (typically a router). When a device sends a packet to the internet, PAT changes the private IP address to the router’s public IP address and appends a unique port number.
- Public to Private – When the response comes back, PAT uses the port number to determine which private IP address and port number the packet should be sent to. Ensuring the packet reaches the correct device on the private network.
With this said, NAT and PAT work together to allow multiple devices on a private network to access the internet using a single public IP address, making the use of available IP addresses more efficient.
