User's Manual

Chapter 10 Network Address Translation (NAT) 129
You may enter a single port number or a range of port numbers to
be forwarded, and the local IP
address of the desired server. The port number identifies a service; for example, web service is on
port 80 and FTP on port 21. In some cases, such as for unknown services or where one server can
support more than one service (for example both FTP and web service), it might be better to specify
a range of port numbers. You can allocate a server IP address that corresponds to a port or a range
of ports. Please refer to RFC 1700 for further information about port numbers.
 Many residential broadband ISP accounts do not allow you to run any server processes
(such as a Web or FTP server) from your location. Your ISP may periodically check for
servers and may suspend your account if it discovers any active services at your location. If
you are unsure, refer to your ISP.
Configuring Servers Behind Port Forwarding (Example)
Let's say you want to assign ports 21-25 to one FTP, Telnet and SMTP server (A i
n the example), port
80 to another (B in the example) and assign a default server IP address of 10.0.0.35 to a third (C in
the example). You assign the LAN IP addresses and the ISP assigns the WAN IP address. The NAT
network appears as a single host on the Internet.
Figure 83 M
ultiple Servers Behind NAT Example
A=10.0.0.33
D=10.0.0.36
C=10.0.0.35
B=10.0.0.34
WAN
LAN
10.0.0.1
IP Address assigned by ISP
10.3.1 The Port Forwarding Screen
Click Network Setting > NAT to open the Port Forwarding screen.
Figure 84 Network Setting
> NAT > Port Forwarding