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P-660R-Tx v2 Series User’s Guide
Chapter 7 Network Address Translation (NAT) Screens 70
Note: 1. Choose SUA Only if you have just one public WAN IP address for your
ZyXEL Device.
2. Choose Full Feature if you have multiple public WAN IP addresses for your
ZyXEL Device.
7.3 SUA Server
A SUA server set is a list of inside (behind NAT on the LAN) servers, for example, web or
FTP, that you can make visible to the outside world even though SUA makes your whole
inside network appear as a single computer to the outside world.
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.
7.3.1 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.
Note: If you do not assign an IP address in Server Set 1 (default server) the ZyXEL
Device discards all packets received for ports that are not specified here or in
the remote management setup.
7.3.2 Port Forwarding: Services and Port Numbers
The most often used port numbers are shown in the following table. Please refer to RFC 1700
for further information about port numbers.
Table 16 Services and Port Numbers
SERVICES PORT NUMBER
ECHO 7
FTP (File Transfer Protocol) 21
SMTP (Simple Mail Transfer Protocol) 25
DNS (Domain Name System) 53
Finger 79