ZyXEL Communications 100 Series User Manual

 Chapter 16 Virtual Servers

ZyWALL USG 100/200 Series User’s Guide

The following sections provide examples of manually configuring NAT 1:1 mapping and a 
policy route rule for NAT loopback. These are provided for your reference, you can select 
options in the Virtual Server Add/Edit screen to have the ZyWALL automatically configure 
these for you instead of configuring them manually.

In this example, there is an SMTP mail server in the LAN1 zone. It has a private IP address of 
192.168.1.21. The public IP address of the server is 1.1.1.1.

In order for the server to be accessible to people from the Internet (WAN zone), you need to 
create a 1:1 NAT mapping from the public IP address to its private one.

The firewall is enabled, so you also need to create a rule to allow traffic in from the WAN 
zone.

Figure 214   NAT 1:1 Example Network Topology

Add 
corresponding 
Policy Route rule 
for NAT 
Loopback.

Select this to allow local users to use a domain name to access this virtual server. 
By default this virtual server entry only applies this address mapping to packets 
coming in from the WAN.
Or you can click Policy Route to go to the screens where you can manually 
configure a NAT loopback policy route for this virtual server.
See 

 for an example of NAT loopback.

Firewall

By default the firewall blocks incoming connections from external addresses. After 
you configure your virtual server rule settings, click the Firewall link to configure a 
firewall rule to allow the virtual server’s traffic to come in.
The ZyWALL checks virtual servers before it applies To-ZyWALL firewall rules, so 
To-ZyWALL firewall rules do not apply to traffic that is forwarded by virtual servers. 
The ZyWALL still checks other firewall rules according to the source IP address 
and mapped IP address.

OK

Click OK to save your changes back to the ZyWALL.

Cancel

Click Cancel to return to the Virtual Server summary screen without creating the 
virtual server (if it is new) or saving any changes (if it already exists).

Table 105   Network > Virtual Server > Edit (continued)