Titan Electronics Inc NETCOM423 Benutzerhandbuch

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NetCom 123 WLAN, 423 WLAN, 
 
9001 and 9000 in this example. Please note, so far there is no number 
for the Virtual Com Port available. The driver is not installed in this 
moment, and Windows does not know about the available hardware. 
This will happen later in the installation. Click the “OK” button, and 
proceed with the driver installation as already described. 
5.2.7.5. 
DMZ and Virtual Servers 
Why is it recommended not to use the DMZ function of the router? 
There are two reasons. The first one is simple, only one device in the 
LAN can be defined as the DMZ target. The DMZ is implemented as 
“Send all IP data targeted for the router to the DMZ station, as long as 
there is no specific rule for a different target”. When a second NetCom 
shall be installed on the LAN, the Virtual Servers have to be configured 
anyway. The second reason is the security. Using the DMZ the Firewall 
in the router becomes transparent. All data from outside is transferred to 
the LAN, including all malicious data. 
5.2.8. D
YNAMIC 
IP A
DDRESS AND 
O
PEN
VPN™ 
Since Firmware version 2.2 there is a different method to provide a 
tunnel to the NetCom. The option of Encryption uses a Virtual Private 
Network (VPN) based on a single TCP connection between the NetCom 
and a client computer. Regardless of strong encryption or even weak as 
not encrypted, here the key point is the single TCP connection. It is 
more simple to provide a Firewall configuration for a single connection, 
so the Router Firewall is more easy to set up. 
The network link established by OpenVPN™ requires to have a target 
address and a port number. Since the basic TCP connection is activated 
by the openvpn.exe program, there is the freedom of using a DNS name 
for the target device. 
With a Dynamic IP Address for the NetCom site, one of the several 
Internet services for Dynamic DNS (DDNS) may help. It is even 
relatively simple to construct an own version. Using this service the 
openvpn.exe program gets the IP Address of the Firewall Router, and 
will establish the link. When the IP Address changes (after 24 hours), 
the connection first gets lost. OpenVPN™ will continuously attempt to 
connect again. When the new IP Address is known via DDNS, the 
network link is re-established. The NetCom is available again. Even 
when a serial port has been open, the function will continue seamlessly.