Translations:IPsec L2TP VPN server/3/en
From Gentoo Wiki
IPsec/L2TP is a commonly used VPN protocol used in Windows and other operating systems. All version of Windows since Windows 2000 have support built-in, not requiring an external client (like OpenVPN does) making it very convenient. However, it is significantly harder to set up on the server side on Linux, as there's at least 3 layers involved: IPsec, L2TP, and PPP.