There is no single standardized VPN tool, although there are moves toward creating VPN standards. In the meantime, organizations that want to configure VPNs need to settle on one of several tools. The three most common tools for Linux are the following:
This chapter focuses on the first two approaches. PPTP is a very popular VPN approach, particularly when Windows clients must connect directly to the VPN router at a central location. There are also PPTP implementations for many other OSs, and even in dedicated hardware devices that are frequently referred to as remote access switches. FreeS/WAN is less popular outside of the Linux world, but it can be an excellent way to link together multiple networks using Linux VPN-enabled routers.