What configuration step is necessary to make a web server on a private LAN accessible on the public Internet?

To allow a web server located on a private LAN to be accessible from the public Internet, configuring destination NAT (dst-nat) in the firewall is essential. This process involves mapping a public IP address to the private IP address of the web server. When users from the Internet try to access the web server's public IP, the NAT router effectively translates those requests and forwards them to the corresponding private IP address of the web server.

This configuration is necessary because private IP addresses are not routable over the Internet. By setting up destination NAT, the router can accept incoming traffic intended for the public IP and direct it to the correct internal server without exposing the private IP directly.

The other options either represent configurations that are not specifically required for making the web server accessible or do not contribute to the NAT process necessary for achieving this goal.