Ever needed to change an existing portforwarding on a Cisco switch / router ? Or needed to add a new portforwarding? This is a short howto..

1) First connect to the switch by telnet

e.g. telnet <<IP or HOSTNAME>> <<PORT; default 23>>

2) Login on the Cisco device with your admin credentials

3) Look at the existing port forwardings:

sh run | i ip nat inside source static

4) Check if you’re portforwarding is there, if not, you can just add a new one

5) Let’s get into the configuration mode

conf t

6 ) If you want to change an existing port forwarding, you must clear the existing translation table

do clear ip nat translation *

7) If you want to change an existing port forwarding, you must remove this one by typing

no ip nat inside source static <<Protocol>> <<IP address>> <<PORT>> <<INTERFACE>> <<LISTEN_PORT>>

Add a new port forwarding by typing

ip inside source static <<Protocol>> <<IP address>> <<PORT>> <<INTERFACE>> <<LISTEN_PORT>>

9) Alow port to be used by typing:

do sh ip acce f0/0-in
ip access-list ex f0/0-in
no 31
31 permit tcp any any eq 80

10) End configure session

CTRL Z

11) Save config

copy run start

12) That’s it!