Port forwarding on a ROBIN gateway is very helpful (say, to remotely manage a subscriber CPE, for example). There are some limitations in how it's implemented in the ROBIN code, though.
1) only 3 TCP forwards and 3 UDP forwards are allowed. This is not only built in the local web interface, but also is hardcoded in ROBIN.
2) Setting a port forward causes the node to reboot. This is problematic for many reasons - in this managed CPE scenario, because you may be trying to check and see why some customer is experiencing a problem. Rebooting their gateway is not a great way to start troubleshooting.
Workaround to these limitations is to ssh into the node and setup a forward manually and on-the-fly:
Edit the file /etc/config/forwarder and set the values under one of the config 'rule' sections:
config 'forwarder' 'rule_2'
option 'IncomingPort' '443'
option 'IPAddr' '188.8.131.52'
option 'DstPort' '443'
This could also be done with uci commands:
uci set forwarder.rule_2.IncomingPort=443
uci set forwarder.rule_2.IPAddr=184.108.40.206
uci set forwarder.rule_2.DstPort=443
uci commit forwarder
Finally, you just need to restart iprules to put the changes into effect: