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

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

Bruce Schneier's FAQ concerning Microsoft's PPTP Implementation
- Bruce Schneier Analysis of the Microsoft PPTP implementation. Why is PPTP bad.
- http://www.schneier.com/pptp-faq.html

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

NG FAQ - VPN with FreeS/WAN - by AERAsec
- This document covers the steps and pitfalls connecting a CheckPoint NG FW-1 to a FreeSWAN Linux-Box using preshared keys and X.509 certificates.
- http://www.fw-1.de/aerasec/ng/vpn-freeswan/CPNG+Linux-FreeSWAN.html

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

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

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

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/

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

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

An Intro To SSL VPN
- An article discusses the types of VPN available, benefits, and considerations necessary when deploying SSL VPNs.
- http://www.hostlibrary.com/node/view/148

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

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

Official IPsec Howto for Linux
- This howto describes the step to take when setting up a Linux based VPN.
- http://www.ipsec-howto.org

Virtual Private Networks (VPN)
- This document discusses key concepts related to Virtual Private Networks
- http://www.rad.net.id/homes/edward/intranet/intra7

L2F
- CISCO's Layer Two Forwarding protocol
- http://cio.cisco.com/warp/public/732/L2F/

What Is A Virtual Private Network?
- A Network Computing Online Article
- http://www.networkcomputing.com/905/905colmoskowitz.html