Cisco 800 series
Our main router for internet access is a Cisco 800 series.
Port forwarding howto
The router's interface is connected only to a separate management VLAN accessible only from the central router. You must first authenticate to it via SSH, then you may log in with root on 172.31.255.2.
Once you have an eco-stiwa prompt:
enable show config
Currently forwarded ports are listed in the lines beginning with "ip nat inside source static"
Now add a new line similar to the existing ones, for example:
ip nat inside source static tcp <internal ip> <internal port> <external ip> <external port> extendable <enter> <ctrl>+z write memory
Check your result with
Remove existing port forwarding rules
Copy a rule from "show config" and paste "no" in front of it.