Chapter 8 Network Address Translation (NAT)
P-870HN-51D User’s Guide
139
Port Forwarding: Services and Port Numbers
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 port forwarding and NAT.
Port Forwarding Example
Let's say you want to assign ports 21-25 to one FTP, Telnet and SMTP server (A in
the example), port 80 to another (B in the example) and assign a default server IP
address of 192.168.1.35 to a third (C in the example). You assign the LAN IP
addresses and the ISP assigns the WAN IP address. The NAT network appears as a
single host on the Internet.
Figure 69 Multiple Servers Behind NAT Example
Table 43 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
D=192.168.1.36
192.168.1.1
IP address assigned by ISP
A=192.168.1.33
B=192.168.1.34
C=192.168.1.35
