TRENDnet TW-H6W1IR - Manual (Page 101)

TW-H6W1IR ISDN Remote Router
Configuration and Management 93
over the Internet and you are using NAPT, you may need to exempt
certain port numbers from the NAPT port translation process. Please
refer to the user guide for the program to find out whether it transmits
and receives data only through specified IP port numbers. In order for
these programs to work with NAPT, the IP port numbers required by
these applications must be entered in the Configure NAPT for Special
APs screen shown below.
In the above window, position the cursor on any of the numbered name
fields and press Enter. This will take you to the NAPT configuration
screen for special applications shown below.