What is the main function of port forwarding in a firewall?

The main function of port forwarding in a firewall is to allow access to internal services from external networks. This process involves configuring the firewall to redirect specific traffic that arrives at a designated port on the firewall to a specific internal IP address and port where a service is running. For example, if a web server is hosted within a private network, port forwarding enables external users to access that server by directing requests to the correct internal address.

In this setup, the firewall plays a crucial role in maintaining security by only permitting the traffic directed toward the designated ports. This means that while the firewall blocks unsolicited traffic, it can still facilitate legitimate connections to services that need to be reachable from outside the network, such as web servers, FTP servers, or remote desktop services. Therefore, the correct answer highlights the essential functionality of port forwarding in enabling external access to internal services while maintaining overall network security.