4. Brief How-to …. Creating Multiple clients to Single site tunnels.
Example of using PKI to create a client-to-site VPN:
For a road warrior or roaming/multiple user scenario, static keys based VPNs don’t scale well. You will need to implement a PKI if you have Hub and Spoke architecture of VPN.
From the OpenVPN.net website:
Static Key advantages

Simple [...]

3. Brief How-to ….. OpenVPN and Site-to-Site Tunnels.
OpenVPN can be implemented either Site-to-site or client-server model. I will take example configurations of both models.
If you want to implement site-to-site configuration, the best way is to use static-keys instead of PKI. Using static keys, you can have your VPN tunnel up and running in a jiffy.
First, [...]

2. Why OpenVPN
Here, in this article, I will lay down the emphasis on one important Open-Source SSL VPN software written by James Yonan and contributed by several others, which proposes security without the inherent complexity of IPsec AND using a trusted design of client component and VPN server.
Usually VPNs require end points which are trusted. [...]

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 [...]