A virtual private network (VPN) is a private network that spreads across a public network like the Internet. This private network allows specified computers to transfer data securely across shared or public networks. The VPN is established through a virtual point-to-point connection using dedicated connections and encryption. Virtual Private Networks are secure pipelines (typically encrypted) that can connect remote employees to central servers.
A virtual private network allows users to access resources in the same way as they would from a traditional private network. This is helpful for many businesses because it allows employees that work remotely to securely access their company’s intranet while working outside the office. VPNs also connect business offices in different geographical locations securely and cost-effectively, creating one unified virtual network. 
There are many reasons to set up a VPN in a business or home environment:
- Connect securely to a remote network via the Internet to access files, applications, printers, and other resources on a business or home network without compromising the network security.
- Connect multiple networks in different locations in a secure manner to share servers and other resources. VPNs can also connect multiple home or personal networks.
- Protect online privacy for personal use or for businesses. These private networks can provide security by connecting to an encrypted VPN if you are on a public network.
- Prevent Having Your Searches Logged By Search Engines:
Google, Bing, and a multitude of other search engines keep track and catalog every web search you do. The search engines attach your online searches to your computer’s specific IP address. This information is then used to customize advertising and future searches for your laptop or desktop.
Common VPN Protocols:
Point-to-Point Tunneling Protocol or PPTP–>
PPTP is a network protocol for connecting to VPNs. In PPTP, the point-to-point protocol (PPP) is combined with the TCP/IP protocol, which provides the Internet connection. Therefore, even though the connection is created over the Internet, the PPTP connection mimics a direct link between the two locations, allowing for a secure connection.
PPTP clients connect to their ISPs using PPP to establish Internet links using point-to-point connections via dial-up modems or DSL. PPTP creates a TCP connection between a VPN client and VPN server to establish a tunnel.
TCP/IP is the foundation for how the Internet works; it stands for “Transmission Control Protocol/Internet Protocol” and allows computers to communicate in networks over long distances.
This method is the least secure way to set up a VPN but it is the easiest to use because most operating systems support it, including Windows, Mac OS, and mobile OSs.
L2TP or Layer 2 Tunneling Protocol & IPSec or Internet Protocol Security –>
Secure Sockets Layer or SSL–>
A SSL (Secure Sockets Layer) establishes an encrypted connection between a server and a client—usually through a website or email. Most SSL VPN servers are designed to provide remote access to your network using a Web browser, while creating encrypted channels for secure remote access to specified servers from any location. This means a dedicated VPN is not necessary for a client to connect to a SSL VPN, and they are usually referred to as “clientless”. 
OpenVPN is an open-source VPN system. This VPN is free and a secure method for a SSL based connection tunnel. This type of VPN is not known to have connection issues however OpenVPN will require a client download on Windows, Mac OS X, and mobile Oss since these operating systems do not natively support it.
OpenVPN uses a custom security protocol to create secure point-to-point connections in routed or bridged configurations and for remote access. This type of VPN is robust and highly flexible.
- SSL/TLS Security
- Ethernet Bridging:
Ethernet Bridging combines an Ethernet interface with one or more virtual TAP interfaces and bridges them together to create one, unified, bridge interface. An Ethernet Bridge acts as a software switch; it can be used to connect multiple Ethernet interfaces (both physical and virtual) on a single computer / server while still sharing one IP subnet.
Tap interfaces are software-based interfaces, and exist only in the kernel. Unlike most network interfaces these types have no physical hardware component to connect to. A TAP device for the host operating system acts like a normal network interface; a portal for a virtual LAN network of QEMU hosts. QEMU hosts can emulate the role of network cards (NICs), and establish virtual LANs (VLAN). 
- UDP tunnel transport through proxies or NAT:
UDP (User Datagram Protocol) allows computer applications to send messages, or datagrams, to other hosts on an Internet Protocol (IP) network without having prior communications, special transmission channels, or data paths set up.
- Dynamic IP Addresses
- DHCP (Dynamic Host Configuration Protocol)
- If you simply need remote access to one computer, you can most likely use the VPN software built into the Windows or Mac operating systems.
- If you need to network multiple computers together, you may need to consider using a standalone VPN server software.
- If you need a more reliable and robust solution supporting site-to-site connections, you may need to use a dedicated VPN router.
- If you want to use a VPN to secure your Internet traffic while you are connected to untrusted networks such as public Wi-Fi hotspots—or need to access regionally restricted sites—you can subscribe to a third-party hosted VPN provider.
Geier, Eric. “How (and why) to set up a VPN today.” PCWorld. IDG Consumer & SMB. (19 March 2013). (29 Sept 2013). <http://www.pcworld.com/article/2030763/how-and-why-to-set-up-a-vpn-today.html>