ZyXEL Communications NBG410W3G Series User Manual

 Chapter 12 Network Address Translation (NAT)

NBG410W3G Series User’s Guide

Figure 142   Multiple Servers Behind NAT Example

The ZyXEL Device has two WAN interfaces. You can configure port forwarding and trigger 
port rule sets for the first WAN interface and separate sets of rules for the second WAN 
interface. 

The ZyXEL Device can translate the destination port number or a range of port numbers of 
packets coming from the WAN to another destination port number or range of port numbers on 
the local network. When you use port forwarding without port translation, a single server on 
the local network can use a specific port number and be accessible to the outside world 
through a single WAN IP address. When you use port translation with port forwarding, 
multiple servers on the local network can use the same port number and still be accessible to 
the outside world through a single WAN IP address.
The following example has two web servers on a LAN. Server A uses IP address 192.168.1.33 
and server B uses 192.168.1.34. Both servers use port 80. The letters a.b.c.d represent the 
WAN port’s IP address. The ZyXEL Device translates port 8080 of traffic received on the 
WAN port (IP address a.b.c.d) to port 80 and sends it to server A (IP address 192.168.1.33). 
The ZyXEL Device also translates port 8100 of traffic received on the WAN port (also IP 
address a.b.c.d) to port 80, but sends it to server B (IP address 192.168.1.34). 

"

In this example, anyone wanting to access server A from the Internet must use 
port 8080. Anyone wanting to access server B from the Internet must use port 
8100.

A=192.168.1.33

D=192.168.1.36

C=192.168.1.35

B=192.168.1.34