User`s manual

Moxa C Programmable RTU Controllers Managing Communications

4-18

Setup 1: Ethernet Bridging for Private Networks on Different Subnets

1. Set up four machines, as shown in the following diagram.

Host A (B) represents one of the machines that belongs to OpenVPN A (B). The two remote subnets are

configured for a different range of IP addresses. When this setup is configured to a public network, the external

interfaces of the OpenVPN machines should be configured for static IPs, or connect to another device (such as

a firewall or DSL box) first.

# openvpn --genkey --secret secrouter.key

Copy the file that is generated to the OpenVPN machine.

2. Generate a script file named openvpn-bridge on each OpenVPN machine. This script reconfigures

interface “eth1” as IP-less, creates logical bridge(s) and TAP interfaces, loads modules, enables IP

forwarding, etc.

#---------------------------------Start-----------------------------

#!/bin/sh

iface=eth1 # defines the internal interface

maxtap=`expr 1` # defines the number of tap devices. I.e., # of tunnels

IPADDR=

NETMASK=

BROADCAST=

# it is not a great idea but this system doesn’t support

# /etc/sysconfig/network-scripts/ifcfg-eth1

ifcfg_vpn()

{

while read f1 f2 f3 f4 r3

if [ “$f1” = “iface” -a “$f2” = “$iface” -a “$f3” = “inet” -a “$f4” = “static” ];then

i=`expr 0`

while :

if [ $i -gt 5 ]; then

break

i=`expr $i + 1`

read f1 f2

case “$f1” in

address ) IPADDR=$f2