PortMapping

Port mapping, also known as port forwarding, is a network address translation (NAT) technique used to direct incoming network traffic from a public IP address and port to a specific private IP address and port within a local network. When a device on the internet attempts to connect to a service running on a local machine, the router or firewall intercepts the request. It then consults its port mapping rules to determine which internal device should receive the traffic. Without port mapping, devices on the internet would only be able to access services directly exposed on the router's public IP address.

This process is essential for allowing external access to services hosted on internal networks, such as web servers, game servers, or remote desktop connections. For example, if a web server is running on a computer with a private IP address of 192.168.1.100 and listening on port 80, a port mapping rule would be configured on the router to forward incoming traffic on its public IP address's port 80 to 192.168.1.100:80. This enables users outside the local network to access the web server by connecting to the router's public IP address.

Port mapping can be configured manually on most routers and firewalls. It involves specifying the external port, the internal IP address of the target device, and the internal port that the service is listening on. While beneficial for accessibility, improperly configured port mappings can create security vulnerabilities by exposing internal services to the public internet.