OpenVPN using X.509 certificates
This document explains how to deploy a VPN using OpenVPN and OpenSSL. http://www.onlamp.com/pub/a/security/2004/10/21/vpns_and_pki.html
OpenVPN 2.0 HOWTO
This howto describes the setup of the IPsec alternative OpenVPN, which is available for Win32, MacOS X and Unix-based Operating Systems. http://openvpn.net/howto.html
Official IPsec Howto for Linux
This howto describes the step to take when setting up a Linux based VPN. http://www.ipsec-howto.org
Poptop MSCHAP2 ADS
This Howto describes the steps to setup a Linux PopTop PPTP Server using MSCHAPv2. For Authentication either Radius or an Active Directory Domain controller may be used. http://www.members.optushome.com.au/~wskwok/poptop_ads_howto_1.htm
Replacing a Windows PPTP server with Linux
Replacing a Windows PPTP server with Linux PopTop. http://poptop.sourceforge.net/dox/replacing-windows-pptp-with-linux-howto.phtml
Virtual Private Networks (VPN)
This document discusses key concepts related to Virtual Private Networks http://www.rad.net.id/homes/edward/intranet/intra7
Using a Linux L2TP/IPsec VPN server
This document gives you the background and show the steps for implementing an L2TP/IPsec based VPN using Linux, Windows and MacOSX http://www.jacco2.dds.nl/networking/freeswan-l2tp.html
Microsoft's PPTP FAQ
Point-to-Point-Tunneling Protocol (PPTP) is a networking technology that supports multiprotocol virtual private networks (VPN). http://www.microsoft.com/ntserver/ProductInfo/faqs/PPTPfaq.asp
German book covering Linux VPNs
This site offers a german book (pdf) covering Linux VPNs for download. http://www.opensource-training.de/buecher_new.php
Freeswan and a Cisco PIX 501
Creating an interoperable VPN using the free FreeSWAN/Openswan and a Cisco PIX 501. http://www.johnleach.co.uk/documents/freeswan-pix/freeswan-pix.html
Configuring an IPsec tunnel between Openswan and Windows
This document gives you the details how to setup a virtual private network between Linux/Openswan on one side and Microsoft Windows 2000 and XP on the other side. http://www.natecarlson.com/linux/ipsec-x509.php
Highly Available VPNs on Linux
This tutorial covers the setup of a HA-VPN using FreeSWAN or Openswan and the Zebra routing daemon. http://www.freeswan.ca/docs/HA/HA_VPNS_With_FreeSWAN.html
Information about Check Point VPN-1/FireWall-1
This site gives valuable information about the Checkpoint VPN-1 product and its interoperability with other VPN implementations. http://www.fw-1.de/aerasec/index.html
Linux VPN Howto using SSH and PPP
This howto describes the setup of a simple VPN using ssh and ppp. http://www.tldp.org/HOWTO/VPN-HOWTO/
L2F
CISCO's Layer Two Forwarding protocol http://cio.cisco.com/warp/public/732/L2F/