Once a meterpreter shell is obtained on a system a larger range of options is available to the Penetration Tester for accessing the system. In a hypothetical scenario the victim is running a vulnerable mail server on port 25, and we have a remote exploit we wish to use against it. Unfortunately for us it’s behind a firewall. After getting a meterpreter shell via a client side attack we want to somehow bypass the firewall and get access to port 25. Meterpreters portfwd can do this.