NATlaitteet

NATlaitteet is a term used in Finnish to refer to network address translation devices. These are hardware or software implementations that modify the IP address and port information of network packets while they transit across a routing device. NAT is commonly used to allow multiple devices on a private network to share a single public IP address, conserving the limited supply of IPv4 addresses.

The primary function of a NAT device is to remap private IP addresses used within a local area network (LAN) to public IP addresses that are routable on the internet. This process involves maintaining a translation table that keeps track of the mappings between internal and external addresses and ports. When a packet leaves the private network, the NAT device replaces the private source IP address with its own public IP address and updates the source port. Upon receiving a response packet from the internet, the NAT device consults its table to determine which internal device the packet is intended for and translates the destination IP address and port back to the original private ones before forwarding it.

There are several types of NAT, including static NAT, dynamic NAT, and port address translation (PAT), also known as NAT overload. PAT is the most common form, allowing many private IP addresses to share a single public IP address by assigning unique source port numbers to each outgoing connection. NAT plays a crucial role in modern network infrastructure, enabling efficient use of IP addresses and providing a basic level of security by hiding internal network structures from the outside world.