Let’s say you need to direct port 8888 on your external IP address to port 80 on a machine inside your network. You begin this process by logging into the router and running enable and entering config mode.

router> enable
Password: ********
router# conf t
router(config)#

For the sake of simplicity, we’ll assume that there is already a working configuration. If there wasn’t, we’d need to add our internal and external interfaces with a command similar to:

router(config)# ip address outside 71.155.211.233 255.255.255.0
router(config)# ip address inside 192.168.1.1 255.255.255.0

But most likely, this has already been setup. Then you’ll need to know the name of your access-list (providing it has already been created). You can obtain that information by running show access-list. Once you have that information, we’re ready to go.

static (inside,outside) tcp interface 8888 192.168.1.101 www netmask 255.255.255.255 0 0
access-list acl_list permit tcp any interface outside eq 8888
access-group acl_list in interface outside

Now exit conf mode with exit and run wr me to save the changes.