charon-cmd is a simple IKE client (IPsec VPN client). It is available in most linux distributions and is very simple to install and configure.
Install charon-cmd and libcharon-extra-plugins
If you are using debian, run:
$ sudo apt-get install charon-cmd libcharon-extra-plugins
Download the certificate for the CA from the server (the ca.crt file)
Type:
$ sudo charon-cmd --cert /path/to/the/cert/ca.crt --host example.com --identity username
You must replace /path/to/the/cert/ca.crt with the path to the ca.crt file, example.com with the actual hostname, and username with the actual username.
When asked, type in your user's password and press .
To disconnect from the server, press .