Let’s say that there is a laptop connected to a home router. Someone uses the laptop to search for directions to their favorite restaurant. The laptop sends this request in a packet to the router, which passes it along to the web. But first, the router changes the outgoing IP address from a private local address to a public address.
If the packet keeps a private address, the receiving server won’t know where to send the information back to — this is akin to sending physical mail and requesting return service but providing a return address of anonymous. By using NAT, the information will make it back to the laptop using the router’s public address, not the laptop’s private one.
NAT Types
There are three different types of NATs. People use them for different reasons, but they all still work as a NAT.
1. Static NAT : When the local address is converted to a public one, this NAT chooses the same one. This means there will be a consistent public IP address associated with that router or NAT device.
2. Dynamic NAT : Instead of choosing the same IP address every time, this NAT goes through a pool of public IP addresses. This results in the router or NAT device getting a different address each time the router translates the local address to a public address.
3. PAT : PAT stands for port address translation. It’s a type of dynamic NAT, but it bands several local IP addresses to a singular public one. Organizations that want all their employees’ activity to use a singular IP address use a PAT, often under the supervision of a network administrator.
