Linux Networking Cookbook

9.2. Starting and Testing OpenVPN

Problem

You followed the previous recipe and your little test lab works, and you're ready to start running OpenVPN. Now what?

Solution

First, check both OpenVPN machines to see if OpenVPN is already running:

	$ ps ax | grep vpn

If it is, stop it:

	# killall openvpn

Then, open a quick, insecure tunnel between the remote PC and your OpenVPN server with these commands:

	root@xena:~# openvpn --remote 192.168.2.100 --dev tun0 \
	--ifconfig 10.0.0.1 10.0.0.2
	root@stinkpad:~# openvpn --remote 192.168.3.10 \
	--dev tun0 --ifconfig 10.0.0.2 10.0.0.1

This message shows success, and should be seen on both sides of the connection:

	Wed Feb 14 12:53:45 2007 Initialization Sequence Completed

Now, open some new terminals, and try pinging your new virtual IP addresses:

	carla@xena:~$ ping 10.0.0.2
	PING 10.0.0.2 (10.0.0.2) 56(84) bytes of data.
	64 bytes from 10.0.0.2: icmp_seq=1 ttl=64 time=0.421 ms
	64 bytes from 10.0.0.2: icmp_seq=2 ttl=64 time=0.314 ms
	carla@stinkpad:~$ ping 10.0.0.1
	PING 10.0.0.1 (10.0.0.1) 56(84) bytes of data.
	64 bytes from 10.0.0.1: icmp_seq=1 ttl=64 time=0.360 ms
	64 bytes from 10.0.0.1: icmp_seq=2 ttl=64 time=0.317 ms

You may also specify which interface for ping to use:

	carla@xena:~$ ping -I tun0 10.0.0.2
	carla@stinkpad:~$ ping -I tun0 10.0.0.1

Go ahead and give your tunnels a test drive by opening SSH sessions everywhere:

	carla@xena:~$ ssh 10.0.0.2
	carla@stinkpad:~$ ssh 10.0.0.1

Exit your SSH sessions, and hit Ctrl-C to shut down OpenVPN and close the tunnels. ...