Moxa KM-2430-T [41/52] Setup 2 ethernet bridging for private networks on the same subnet

ioPAC RTU Software RTU Communications

4-16

cipher DES-EDE3-CBC

auth MD5 tun-mtu 1500

tun-mtu-extra 64

ping 40

up /etc/openvpn/B-tap0-br.sh

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

#!/bin/sh

# value after “-net” is the subnet behind the remote peer

route add -net 192.168.2.0 netmask 255.255.255.0 dev br0

#---------------------------------- end ------------------------------

NOTE: Select cipher and authentication algorithms by specifying “cipher” and “auth”. To see which

algorithms are available, type:

# openvpn --show-ciphers

# openvpn --show—auths

4. Start both of OpenVPN peers,

# openvpn --config A-tap0-br.conf&

# openvpn --config B-tap0-br.conf&

If you see the line “Peer Connection Initiated with 192.168.8.173:5000” on each machine, the connection

between OpenVPN machines has been established successfully on UDP port 5000.

5. On each OpenVPN machine, check the routing table by typing the command:

# route

Destination Gateway Genmsk Flags Metric Ref Use Iface

192.168.4.0 * 255.255.255.0 U 0 0 0 br0

192.168.2.0 * 255.255.255.0 U 0 0 0 br0

192.168.8.0 * 255.255.255.0 U 0 0 0 eth0

Interface eth1 is connected to the bridging interface br0, to which device tap0 also connects, whereas the

virtual device tun sits on top of tap0. This ensures that all traffic from internal networks connected to

interface eth1 that come to this bridge write to the TAP/TUN device that the OpenVPN program monitors.

Once the OpenVPN program detects traffic on the virtual device, it sends the traffic to its peer.

6. To create an indirect connection to Host B from Host A, you need to add the following routing item:

route add –net 192.168.4.0 netmask 255.255.255.0 dev eth0

To create an indirect connection to Host A from Host B, you need to add the following routing item:

route add –net 192.168.2.0 netmask 255.255.255.0 dev eth0

Now ping Host B from Host A by typing:

ping 192.168.4.174

A successful ping indicates that you have created a VPN system that only allows authorized users from one

internal network to access users at the remote site. For this system, all data is transmitted by UDP packets

on port 5000 between OpenVPN peers.

7. To shut down OpenVPN programs, type the command:

# killall -TERM openvpn

Setup 2: Ethernet Bridging for Private Networks on the Same Subnet

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