ZyXEL Communications P-660R-F1 series, User Manual

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Chapter 6 Network Address Translation (NAT) Screens
P-660R-F1 Series User’s Guide
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6.4 Port Forwarding
A port forwarding 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 NAT 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.
6.4.1 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 a Default Server IP address, the ZyXEL Device discards all
packets received for ports that are not specified here or in the remote management
setup.
6.4.2 Port Forwarding: Services and Port Numbers
Use the Port Forwarding screen to forward incoming service requests to the server(s) on your
local network.
The most often used port numbers are shown in the following table. Please refer to RFC 1700 for
further information about port numbers.
Table 26
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