Port forwarding forwards all traffic on a specific port (or range of ports) from the firewall to a computer on the internal LAN. This can be required to support special situations. For instance, this is the only way to support file transfers with an ICQ client on an internal computer. It's also required if an internal system hosts a service such as a web server. However, it's also a dangerous option. It allows Internet computers access to your internal network. Use it carefully and only if you're certain you know what you're doing.
Easy Firewall Generator supports the creation of a single port forwarding rule (or two if both tcp and udp are selected). If you require additional rules, use the generated rules as a template to build the additional rules in the output script. Be sure to create the appropriate rule both in the PREROUTING chain of the NAT table and the FORWARD chain of the INPUT table.
The following lists may help you determine which ports to forward (open in new tab):