[转载]SSL VPNs and Using OpenVPN

原始连接：http://www.darknet.org.uk/2006/03/ssl-vpns-and-openvpn/

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Requirement: To connect to a VPN server in a different country.

Situation: A country which has proxies at every gateway.

Issues: VPN based on IPSec is fussy when it comes across networks which are NAT’ted/ proxied. The Security Parameters Indexes don’t match and clients do not get connected.

Objective: To connect VPN server in a corporate network using some flexible VPN which I can run on any port/transport protocol so as to bypass the port/protocols/applications restriction.

Using these factors I came to conclusion that I needed SSL VPN solution. The following article explains the SSL VPN nuances and advantages of using them in certain situations.

Contents:

What is an SSL VPN
Why OpenVPN
brief How-to (site-to-site and client to site)
Nutshell

1. What is an SSL VPN
For a very long time, people in information security have thought IPSec is THE VPN and SSL is for secure online banking. While SSL has traditionally been used for Web site security purposes, SSL’s applications reach wider than just web proxying and application security.

Traditional SSL VPN started off with products that were more like SSL gateways instead of true VPNs. These products cannot be really termed as VPN but more like “Secure Remote Application Access”.

They thrive on a management fa