ZyXEL Communications SBG5500 Series User Manual page 137

Chapter 8 Network Address Translation (NAT)
Figure 107 NAT Application With IP Alias
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.
Table 54 Services and Port Numbers
SERVICES
ECHO
FTP (File Transfer Protocol)
SMTP (Simple Mail Transfer Protocol)
DNS (Domain Name System)
Finger
HTTP (Hyper Text Transfer protocol or WWW, Web)
POP3 (Post Office Protocol)
NNTP (Network News Transport Protocol)
SNMP (Simple Network Management Protocol)
SNMP trap
PPTP (Point-to-Point Tunneling Protocol)
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
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PORT NUMBER
7
21
25
53
79
80
110
119
161
162
1723