TRENDnet TW-H6W1IR - Manual (Page 100)

TW-H6W1IR ISDN Remote Router
92 Configuration and
Management
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Port – this is a destination port number used by TCP and UDP to
de-multiplex incoming IP packets.
In the above example, incoming packets with the global destination IP
Address (211.11.22.3) and global destination TCP/UDP port (21) will
be translated to a packet with the local destination IP Address (1.1.1.5)
and local TCP/UDP port (21).
Port 21 is assigned to FTP servers. Please see Appendix C – IP
Protocol and Port Numbers for more commonly assigned port
numbers, or RFC 1700 for a more complete list.
Configure NAPT for Special Ap[plication]s
Some applications programs that are used over the Internet such as
Microsoft NetMeeting, Diablo, CU See Me and Xwindows send
information to a certain port number or within a specified range of port
numbers. The exact port number used is specific to the application.
However, if you find that you are having trouble using an application