ZyXEL Communications P-335WT - Manual (Page 148)

P-335 Series User’s Guide
148 Chapter 9 Network Address Translation (NAT) Screens
9.3.2 Port Forwarding: Services and Port Numbers
A NAT server set is a list of inside (behind NAT on the LAN) servers, for example, web or
FTP, that you can make accessible to the outside world even though NAT makes your whole
inside network appear as a single machine to the outside world.
Use the SUA Server page to forward incoming service requests to the server(s) on your local
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.
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.
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.
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 45 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