Titan Electronics Inc NETCOM423 Manuel D’Utilisation

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823RM WLAN, 1623RM WLAN  
Page 
50 
 
router there is only one public IP-Address on the external side, and 
typically 254 internal IP-Addresses for the LAN side. These internal 
addresses may be assigned by DHCP or static. Such routers offer a 
feature typically named “DMZ”, which in fact is only a single exposed 
host. It is recommended not to use the “DMZ” for several reasons, some 
of them are security related. 
5.2.7.2. 
SOHO Virtual Servers 
The router also offers “Virtual Servers”, which is the option required 
for NetCom installation. These “Virtual Servers” (here named VSrv for 
short) operate by a technique called PAT (Port Address Translation). 
Certain data addressed to the public IP-Address of the router are 
forwarded to the internal private address of the NetCom. The NetCom 
can be contacted via the public IP-Address of the router. 
First you need to configure the router for some VSrvs. As the absolute 
minimum there is one VSrv for the NetCom device itself, and another 
two VSrvs for each serial port of the NetCom. Those VSrv are to be 
configured for TCP or UDP transmissions. Please read in the manual of 
your router how to do that. You need a port for the external interface, 
and an IP-Address plus a port for the LAN side. The IP-Address is of 
course that of the NetCom. As an example the most easy device is a 
NetCom 113. The internal port for SNMP is 161 for UDP. The serial 
port requires ports 2000 and 2001 for TCP. 
Function External port Internal port
SNMP 8161/UDP  161/UDP 
Control 9000/TCP  2000/TCP 
Data 9001/TCP 2001/TCP 
Configure your router for these example VSrvs, and use the internal 
IP-Address of  the NetCom for the targets. Connect the NetCom to your 
LAN. Now you are ready for a very first test. Use Telnet to connect to 
the Data port of the NetCom serial port. Open a console (DOS Box) and 
type the command 
 
  
Telnet <routers-IP-Address> 9001
 
 
You will be connected to the serial port. Every character you type is 
sent out of the serial port, and every received data is shown on your 
screen. The serial parameters are preconfigured in your NetCom.