User guide

SET UP
14 Address and port translation
The RAS-3G provides the capability to replace the original source IP address and the destination
port and IP address in particular situations.
14.1 Port forwarding
Port forwarding consists in transferring the IP frames addressed to the RAS-3G antenna IP address
(WAN IP address) at a particular port number
, to a particular device connected to the LAN interface.
The transfer criteria is the port number; the port number is used as an additional address field.
When a frame is addressed to the RAS-3G router with a particular registered port, it is transferred to
a particular device connected to the LAN interface.
Example :
Let us suppose the PC named “W1” connected to the Internet has to send frames to the device PLC1
connected to one Ethernet port of the RAS-3G router.
If a VPn cnnot be set, the solution can be to use the Port forwarding function :
When W1 needs to transmit frames to PLC1, it addresses the frames to the RAS-3G router on a
chosen and agreed port.
The router checks the frame, replaces the destination address by the IP address of the device on the
LAN interface, and eventually changes the port number.
PLC1 192.168.0.15
TCP/102; TCP/80
PLC2 192.168.0.16
TCP/502
PC 192.168.0.17
TCP/80
3G
INTERNET
WAN IP addr. :
62.10.10.7
my_machine.dyndns.org
The port forwarding table will be
IP frames received by the router on its 3G
interface (WAN)
Modified forwarded freme
@IP Port Device IP@ Port
62.10.10.7 102 192.168.0.15 102
62.10.10.7 8080 192.168.0.15 80
62.10.10.7 502 192.168.0.16 502
62.10.10.7 80 192.168.0.17 80
Remark :
Port forwarding, ican be used only if the address assigned to the RAS-3G router over the 3G network
is a public IP address.
If it is a dynamic IP address, DynDNS can be used.
Port farwarding is a security defect; it must be used only if the devices conncetd to the LAN interface
of the RAS-3G are themselves protected (password ...) and not dangerous.
Page 50 User guide ref 9020009-01 UMTS GPRS EDGE router ref. RAS-3G