View source for Howto/Setup Bridged OpenVPN server on Ubuntu 10.04

I want my users to be able to access my network remotely as if they were locally. Also, I want client side configuration steps kept to a minimum. Specifically, I want clients to use the "alternative OpenVPN authentication method". Also, I want clients to be able to see all machines on the server's side (this last bit was what cost me a LOT of time to figure out). Last but not least, I do NOT want all traffic being forwarded through the VPN.

== My setup ==
* The following was tested on '''OpenVPN 2.1''' but may work for other version
* I have a standard router that acts as my gateway, located at '''192.168.8.1'''
* My OpenVPN server has '''one NIC on eth0''' and its ip address is '''192.168.8.141''' and it is using the default '''UDP 1194''' port
* My router is setup to assign ip addresses upon requests via '''dhcp''' in the range 192.168.8.100 to 192.168.8.199, and my servers have '''static leases'''.
* The OpenVPN server will be responsible for handing out ips to clients in the range 192.168.8.5 to 192.168.8.99

== The Steps ==
Using the following as a guide,
 https://help.ubuntu.com/lts/serverguide/openvpn.html
 https://help.ubuntu.com/10.04/serverguide/C/openvpn.html
 https://help.ubuntu.com/10.04/serverguide/C/network-configuration.html#bridging

; Step 1) Install prerequisites
 sudo apt-get install openvpn bridge-utils easy-rsa

; Step 2) Install a virtual bridged adapter
Modify /etc/network/interfaces
<pre>
# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth0
iface eth0 inet manual

# bridge, if router can lease static ips (static ip: 192.168.8.141)
auto br0
iface br0 inet dhcp
        bridge_ports eth0
        bridge_fd 9
        bridge_hello 2
        bridge_maxage 12
        bridge_stp off

## bridge, if router cannot lease static ips
#auto br0
#iface br0 inet static
#        address 192.168.8.141
#        network 192.168.8.0
#        netmask 255.255.255.0
#        broadcast 192.168.8.255
#        gateway 192.168.8.1
#        bridge_ports eth0
#        bridge_fd 9
#        bridge_hello 2
#        bridge_maxage 12
#        bridge_stp off
</pre>
Restart networking
 sudo /etc/init.d/networking restart

; Step 3) Create the server certificates
Follow the directions
 https://help.ubuntu.com/10.04/serverguide/C/openvpn.html

; Step 4) Configure the server
Note: Do not create client certificates as we wish to only authenticate with a username and password as per the instructions at
http://openvpn.net/index.php/open-source/documentation/howto.html#auth
Specifically, start by getting a sample config file
 sudo cp /usr/share/doc/openvpn/examples/sample-config-files/server.conf.gz /etc/openvpn/
 sudo gzip -d /etc/openvpn/server.conf.gz
Then modify the server.conf
<pre>
local 192.168.8.141
dev tap0
;dev tun
;server 10.8.0.0 255.255.255.0
server-bridge 192.168.8.141 255.255.255.0 192.168.8.5 192.168.8.99
push "route 192.168.8.0 255.255.255.0"
push "dhcp-option DNS 192.168.8.1"
client-to-client
duplicate-cn
;tls-auth ta.key 0
user nobody
group nogroup
plugin /usr/lib/openvpn/openvpn-auth-pam.so login
client-cert-not-required
username-as-common-name
up "/etc/openvpn/up.sh br0"
down "/etc/openvpn/down.sh br0"
push "ip-win32 dynamic 0 3600"
</pre>

Create the up.sh and down.sh scripts as per the Ubuntu guide 
 https://help.ubuntu.com/10.04/serverguide/C/openvpn.html
place them in /etc/openvpn and make them executable
 sudo chmod 755 /etc/openvpn/down.sh
 sudo chmod 755 /etc/openvpn/up.sh

Here was the part that took me MANY HOURS to figure out as it was only by browsing the OpenVPN FAQ that I figured it out. For clients to see all machines on the server's side, edit /etc/sysctl.conf
 net.ipv4.ip_forward=1

Restart the server for changes to take effect.

; Step 5) Forward ports on the router
Forward requests for port 1194 on the router to the ip address of the server via the router's web interface.

; Step 6) On another machine outside the network, install the client
For Ubuntu it is already installed after doing
 sudo apt-get install openvpn
For Windows, get the complete installation package here
 http://openvpn.se/download.html

; Step 6) Configure the client
Get a sample config file. On Ubuntu, it is located here
 /usr/share/doc/openvpn/examples/sample-config-files/client.conf
and, if run as a daemon, it must be placed in /etc/openvpn along with the ca.crt file that was generated in Step 3.

On Windows, it is located at 
 C:\Program Files\OpenVPN\sample-config\client.opvn
and it must be placed in
 C:\Program Files\OpenVPN\config
along with the ca.crt file that was generated in Step 3.
Modify the following lines in client.conf or client.opvn
<pre>
dev tap
;dev tun
remote www.interpause.com 1194
user nobody
group nobody
;cert client.crt
;key client.key
;tls-auth ta.key 1
auth-user-pass
</pre>

; Step 7) Start the client
On Ubuntu, it can be started as a daemon or at the command prompt using 
 sudo openvpn --config client.conf

On Windows, reload the GUI and there should be a Connect option that appears if the config file and the ca.crt certificate and in the correct place.

You should be able to ping and access any shares located on the server's side.

; Troubleshooting Tip
On an Ubuntu server and client, instead of running the server (and client) as a daemon, execute it at the command prompt using
 sudo openvpn --config server.conf --script-security 2
and observe the output.