Now that the configuration file exists, you can simply run sudo vpnc enp.conf (or leave off the .conf). You will now be connected to the VPN. If everything worked, and you will notice a new 'tun' interface in the 'ifconfig' output.

To disconnect from the VPN, simply run sudo vpnc-disconnect

Do note that the default route gets replaced with the VPN router (so all traffic goes through the VPN) when you are connected. See the vpnc man page for help changing this behavior, or simply remember to disconnect from the VPN when you are done.

Pro Tip: if you have established SSH connections, they will drop when you connect to the VPN. To avoid this, do not let vpnc change your default route. Configure vpnc to add just the routes to the networks you wish to access via the VPN, ensuring you specify tun0 as the interface. All your normal traffic will survive VPN connects and disconnects, including your existing SSH sessions (assuming they are not to IPs within the range of the VPN network).

Using NetworkManager

To create a new VPN connection using GNOME's NetworkManager, click the network icon in the upper-right hand corner of the screen, then select VPN Connections -> Configure VPN. Click "Add" to create a new VPN connection.

If the NetworkManager vpnc plug-in is installed, you will be able to select the Cisco VPN option. The next screen will require that you enter the above mentioned information for the VPN connection. The GUI also presents you with the option to save your password.

After you click Apply, you're done. To connect to the VPN, simply select the VPN name you entered via the NetworkManager Gnome applet under VPN Connections, and it will connect automatically.

When he's not writing for Enterprise Networking Planet or riding his motorcycle, Charlie Schluting is the Associate Director of Computing Infrastructure at Portland State University. Charlie also operates OmniTraining.net, and recently finished Network Ninja, a must-read for every network engineer.

Article courtesy of Enterprise Networking Planet

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