Let us see VPN situations in more detail.

VPNs provide remote access to corporate resources over the public Internet, while maintaining privacy of information. VPN used to connect a remote user to a corporate intranet.

Rather than making a long distance (or 1-800) call to a corporate or outsourced Network Access Server (NAS), the user calls a local ISP. Using the connection to the local ISP, the VPN software creates a virtual private network between the dial-up user and the corporate VPN server across the Internet.

There are two methods for using VPNs to connect local area networks at remote sites:

Using dedicated lines to connect a branch office to a corporate LAN. Rather than using an expensive long-haul dedicated circuit between he branch office and the corporate hub, both the branch office and the corporate hub routers can use a local dedicated circuit and local ISP to connect to the Internet. The VPN software uses the local ISP connections and the Internet to create a virtual private network between the branch office router and corporate hub router.

Using a dial-up line to connect a branch office to a corporate LAN. Rather than having a router at the branch office make a long distance (or 1-800) call to a corporate or outsourced NAS, the router at the branch office can call the local ISP. The VPN software uses the connection to the local ISP to create a VPN between he branch office router and the corporate hub router across the Internet.



In both cases, the facilities that connect the branch office and corporate offices to the Internet are local. The corporate hub router that acts as a VPN server must be connected to a local ISP with a dedicated line. This VPN server must be listening 24 hours a day for incoming VPN traffic.

In some corporate internetworks, the departmental data is so sensitive that the department’s LAN is physically disconnected from the rest of the corporate internework. Although this protest the department’s confidential information, it creates information accessibility problems for those user not physically connected to the separate LAN.

VPNs allow the department’s LAN to be physically connected to the corporate internetwork but separated by a VPN server. The VPN server is not acting as a router between the corporate internetworks and the department LAN. A router would connect the two networks, allowing everyone access to the sensitive LAN. By using a VPN, the network administrator can ensure the only those users on the corporate internetwork who have appropriate credentials (based on a need to-know policy within the company) can establish a VN with the VPN server and gain access to the protected resources of the department. Additionally, all communication across the VPN can be encrypted for data confidentiality. Those users who do not have the proper credentials cannot view the department LAN.



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