Prestige 623ME-T User’s Guide

Figure 5-2 Multiple Servers Behind NAT Example

Please note that a server can support more than one service, e.g., a server can provide both FTP and DNS service, while another provides only web service. Also, since you need to specify the IP address of a server in the Prestige, a server must have a fixed IP address and not be a DHCP client whose IP address potentially changes each time it is powered on.

In addition to the servers for specific services, SUA supports a default server. A service request that does not have a server explicitly designated for it is forwarded to the default server. If the default server is not defined, the service request is simply discarded.

The most often used port numbers are described in the following table:

Table 5-1 NAT Mode

SERVICES

PORT NUMBER

 

 

FTP (File Transfer Protocol)

21

 

 

Telnet

23

 

 

SMTP (Simple Mail Transfer Protocol)

25

 

 

DNS(Domain Name System)

53

 

 

HTTP (Hyper Text Transfer Protocol or WWW, Web)

80

 

 

PPTP (Point-to-Point Tunneling Protocol)

1723

 

 

NAT

5-3