Linux Journal: Setting up a VPN Gateway

“A virtual private network (VPN) is a tool that enables
the secure transmission of data over untrusted networks such as the
Internet. VPNs commonly are used to connect local area networks
(LANs) into wide area networks (WANs) using the Internet. Perhaps
you need to build a VPN between two offices but are not sure if the
large infrastructure costs associated with an enterprise-level VPN
solution are justifiable. The performance of applications that are
intended for use over LANs (for example those that use network file
sharing) seriously can be degraded over WAN connections. Likewise,
lower bandwidth and longer latency in WAN connections can affect
adversely the reliability and performance of groupware and
thin-client applications. Perhaps you have a home office and would
like to use your high-speed internet access to connect seamlessly
and securely to your office LAN through an IPSec-capable router. Or
perhaps you are just curious about VPNs and IPSec in general and
want to experiment.

The VPN firewall discussed in this article will run on just
about any 486-or-better PC that has 16MB or more main memory and
two Linux-compatible Ethernet network cards. The idea is to provide
a starting point from a single, self-contained package that will
allow you to create robust, secure, scalable and highly
configurable VPNs that also are interoperable with many common
commercial VPN implementations. If you wish to experiment on a
low-maintenance firewall-VPN gateway, then the package discussed
here might be ideal for you.

This article shows you how to set up, at minimal expense, a
working VPN gateway that uses the IETF’s (Internet Engineering Task
Force) IPSec (internet protocol security) specification. IPSec is
an open standard and is supported by virtually all major firewall
software and hardware vendors, such as Lucent, Cisco, Nortel and
Check Point. This package will give you a widely interoperable
IPSec that uses the de facto standard 3DES encrypted,
MD5-authenticated site-to-site or point-to-site VPN. You should be
able to do this without resorting to a full Linux distribution or
recompiling a standard Linux kernel with a kernel IPSec
module.”

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