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P-320W User’s Guide
102 
Chapter 8 Network Address Translation (NAT)
Note: If you do not assign a Default Server IP Address, the Prestige discards all 
packets received for ports that are not specified in this screen or remote 
management.
8.1.6  Port Forwarding: Services and Port Numbers
A SUA 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 Port Forwarding 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 41   Services and Port Numbers
SERVICE
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