A virtual private network (VPN) is a way to use a public telecommunication infrastructure, such as the Internet, to provide remote offices or individual users with secure access to their organization's network. A virtual private network can be contrasted with an expensive system of owned or leased lines that can only be used by one organization. The main benefit of a VPN is the lower cost needed to support this technology compared to alternatives like traditional leased lines or remote access servers.
VPN is typically used for following scenarios:
1. To support remote access to an intranet
2. To support connections between multiple intranets within the same organization
3. To join networks between two organizations, forming an extranet
There are two types of VPN technology: Client-to-LAN and LAN-to-LAN
Client-to-LAN VPN technology is generally implemented through software running on a user's notebook computer. It can be implemented through the use of a separate VPN card or separate device; however, this is not as commonly used for individual computers using a VPN. Client-to-LAN VPNs are the most common type of VPNs used by individual computers in remote locations.
LAN-to-LAN VPN technology most often utilizes hardware VPN routers to establish a virtual network between two or more independent LANs. This type of VPN is most often used for meetings at remote locations where multiple computers will be used, or for remote offices that require that people at the main office and the remote office can access both networks.
References: TechTarget CompNetworking NauticalWireless