ZyXEL Communications P-2802H-I Series, User Manual

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Chapter 9 Network Address Translation (NAT) Screens
P-2802H(W)(L)-I Series User’s Guide
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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.
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.
9.4.1 Default Server IP Address
In addition to the servers for specified services, NAT supports a default server IP address. A
default server receives packets from ports that are not specified in this screen.
"
If you do not assign a Default Server IP address, the ZyXEL Device discards
all packets received for ports that are not specified here or in the remote
management setup.
9.4.2 Port Forwarding: Services and Port Numbers
Use the Port Forwarding screen to forward incoming service requests to the server(s) on your
local network.
The most often used port numbers and services are shown in
Appendix E on page 373 . Please
refer to RFC 1700 for further information about port numbers.
9.4.3 Configuring Servers Behind Port Forwarding (Example)
Let's 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
192.168.1.35 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.