WESTELL 327W Modem and VPN

If I set my Westell 327W Modem to Medium security it will not allow my VPN to work. I believe I need to open Ports 47 and 1723 to do this. I don’t understand the firewall’s scripting language to be able to do this. Does anyone know how to do this? Is there a resource that will descibe the scripting language for the firewall?