Draytek Vigor 2200VG User Manual page 42

On the page, you will see the private IP address defined in RFC-1918.
Usually we use the 192.168.1.0/24 subnet for the router. Also, as stated
before, the NAT facility can map one or more IP addresses and/or service
ports into different specified services. In other words, the NAT function
can be achieved by using port mapping method.
In the Vigor routers, we support three variants of port mapping methods:
Port Redirection, Open Ports, and DMZ host
Port Redirection
Open Ports
DMZ host
It should be noticed that, while you are using combinations of these three
systems, there is a priority structure. That is, if a rule in one method
conflicts with a rule in another method, then there is strict precedence. This
leads to a predictable result and resolution of rule-conflict. The precedence
is defined as follows.
Port Redirection > Open Ports > DMZ host
Example: If the port number of an incoming packet matches a rule
specified in both Port Redirection and Open Ports, then the packet will be
forwarded to the local address designated in Port Redirection.
Now, let us move on individual setting of these three port-mapping
NAT Setup
The packet is forwarded to a specific local host if the port
number matches that defined in the table. A user can also
translate the port to another port locally.
Similar to the Port Redirection, the Open Ports facility also
supports users to define a range of ports.
This opens up a single host completely. All incoming packets
will be forwarded to the host with the local IP address you
designated. The only exception is packets received in
response to outgoing requests from other local computers or
incoming packets that match rules in the other two methods.
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