ZyXEL Communications NBG7815, User Manual, Page: 94 / 186

Chapter 9 WAN
NBG7815 User’s Guide
94
9.5 NAT and Port Forwarding
Use Port Forwarding to forward incoming service requests from the Internet to the servers on your local
network. Port forwarding is commonly used when you want to host online gaming, P2P file sharing, or
other servers on your network.
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.
Note: TCP port 7547 is reserved for system use.
Note: 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 us say you want to assign ports 21 – 25 to one FTP, Telnet and SMTP server ( A in the example), port 80
to another ( B in the example) and assign a default server IP address of 192.168.123.35 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 46 Multiple Servers Behind NAT Example