Moxa UC-8416-T-LX [44/90] Openvpn

UC-8410/8416/8418/8430 Managing Communication

4-17

OpenVPN

OpenVPN provides two types of tunnels for users to implement VPNS: Routed IP Tunnels and Bridged

Ethernet Tunnels. To begin with, check to make sure that the system has a virtual device /dev/net/tun. If

not, issue the following command:

# mknod /dev/net/tun c 10 200

An Ethernet bridge is used to connect different Ethernet networks together. The Ethernets are bundled into one

bigger, “logical” Ethernet. Each Ethernet corresponds to one physical interface (or port) that is connected to the

bridge.

On each OpenVPN machine, you should generate a working directory, such as /etc/openvpn, where script

files and key files reside. Once established, all operations will be performed in that directory.

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 moved 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. The openvpn-bridge script file located at “/etc/openvpn/” reconfigures the interface “eth1” as IP-less,

creates logical bridge(s) and TAP interfaces, loads modules, and enables IP forwarding.

#---------------------------------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()