Virtual Private Networks, Second Edition

Chapter 8. Creating a VPN with the Unix Secure Shell

Unix has long been the development platform for the Internet. Everything from the TCP/IP suite to HTTP was developed on Unix first. Much of the development for private LAN-to-LAN connections, including IPSec and IPv6, is taking place on Unix platforms.

In addition, the Linux operating system has become an important Internet server and development platform. Linux, a Unix-like OS, is freely available over the Internet, or can be purchased on CD for a modest price from a number of sources. Linus Torvalds created Linux as a non-commercial alternative to the other flavors of Unix available on Intel-based platforms. Linux became popular thanks to ISPs, web presence providers, and universities choosing it to deliver Internet services. Although originally shunned by large businesses because of a perceived lack of support, it has since garnered applications support from companies such as Corel and Netscape. In 1998, it was estimated that as many as seven million people worldwide use the OS. Linux’s proliferation has meant that more and more networks are running a Unix OS variant, often as a web server, router, or proxy server.

The Secure Shell (SSH) is a replacement for insecure methods of accessing a remote Unix host. It’s meant to replace the common Unix tools rsh, rcp, and rlogin, and can also replace telnet in many cases. Its open-ended versatility means that it can also accomplish things like forwarding secure X11 connections and copying ...