ZyXEL Communications ZyXEL ZyAIR 100 - Manual (Page 129)

ZyWALL 10~100 Series Internet Security Gateway
NAT 9-7
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.
In addition to the servers for specified services, NAT supports a default server. A service request that does
not have a server explicitly designated for it is forwarded to the default server. If the default is not defined,
the service request is simply discarded.
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.
The most often used port numbers are shown in the following table. Please refer to RFC 1700 for further
information about port numbers. Please also refer to the Supporting CD for more examples and details on
SUA/NAT.
Table 9-3 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
HTTP (Hyper Text Transfer protocol or WWW, Web) 80
POP3 (Post Office Protocol) 110
NNTP (Network News Transport Protocol) 119
SNMP (Simple Network Management Protocol) 161
SNMP trap 162
PPTP (Point-to-Point Tunneling Protocol) 1723
9.3.2 Configuring Servers Behind SUA (Example)
Let's say you want to assign ports 22-25 to one server, port 80 to another and assign a default server IP
address of 192.168.1.35 as shown in the next figure.