Chapter 12 Network Address Translation (NAT)
VSG1435-B101 Series User’s Guide
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12.8.4 NAT Application
The following figure illustrates a possible NAT application, where three inside LANs
(logical LANs using IP alias) behind the ZyXEL Device can communicate with three
distinct WAN networks.
Figure 75 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 52 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
