ZyXEL Communications ZyWALL 300 User Manual

Chapter 6 Tutorials

ZyWALL USG 300 User’s Guide

When a LAN user sends SMTP traffic to IP address 1.1.1.1, the traffic comes into the 
ZyWALL through the ge1 (LAN) interface, thus it does not match the NAT 1:1 mapping’s 
virtual server rule for SMTP traffic coming to IP 1.1.1.1 from ge3 (the WAN). So you must 
configure a similar virtual server rule for ge1. 

Figure 98   NAT Loopback Virtual Server

Click Network > Virtual Server and the + symbol and create the virtual server rule as shown 
next. This virtual server rule is the same as the NAT 1:1 virtual rule in 

, except you use the LAN interface (ge1) instead of the WAN interface (ge3). This rule 

maps TCP port 25 (SMTP) traffic destined for IP address 1.1.1.1 and coming in on ge1 to the 
IP address of the SMTP server (192.168.1.21). In this example the SMTP server also uses port 
25, so the Mapped Port is set to 25.

Figure 99   Create a Virtual Server