When setting up port forwarding using NETGEAR Genie, I can specify up to 4 different ports for each forwarding:
- External Start Port
- External End Port
- Internal Start Port
- Internal End Port
If you could only specify two ports (eg. external and internal), I would assume that the router would check if the port specified in the packet matched the external port and if so, it would rewrite the packet with the internal port and send it to the specified local ip address.
What do each of these mean? Which are conditions and which are rewriting rules?