Draytek Vigor 3100 Series User Manual page 40

The inherent security properties of NAT are somewhat bypassed if you set up DMZ
host. We suggest you to add additional filter rules or a secondary firewall.
Click DMZ Host to open the following page:
Enable
Private IP
Choose PC
34
Check to enable the DMZ Host function.
Enter the private IP address of the DMZ host, or click Choose PC to
select one.
Click this button and then a window will automatically pop up, as
depicted below. The window consists of a list of private IP addresses
of all hosts in your LAN network. Select one private IP address in
the list to be the DMZ host.
Vigor3100 Series User's Guide