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Prestige 310 Broadband Sharing Gateway
Network Address Translation (NAT)
6-13
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 included disk for more examples and details on
NAT.
Table 6-7 Services & Port Numbers
SERVICES
PORT NUMBER
ECHO
7
FTP (File Transfer Protocol)
21
Telnet
23
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
6.4.1 Configuring a Server behind NAT
Follow these steps to configure a server behind NAT:
Step 1.
Enter 15 in the main menu to go to
Menu 15 — NAT Setup.
Step 2.
Enter 2 to go to
Menu 15.2 — NAT Server Setup
.
Step 3.
Enter a port number in an unused
Start Port No
field. To forward only one port, enter it again in
the
End Port No
field. To specify a range of ports, enter the last port to be forwarded in the
End
Port No
field.
Step 4.
Enter the inside IP address of the server in the
IP Address
field. In the following figure, you have
a computer acting as an FTP, Telnet and SMTP server (ports 21, 23 and 25) at 192.168.1.33.