This is a quickie.
How do I access a Cloudstack network with VPN from Linux?
Well thats easy.
Install and configure l2tp-ipsec-vpn like they describe in this article
There is a bug in L2tpIPsecVPN which apparently doesn’t send the password correctly. After adding new or editing existing connections, you need to add your user’s password into /etc/ppp/connection-name.options.xl2tpd