Introduction

Virtual private networks (VPNs) are quickly supplanting leased lines as a cost-effective and practical way of providing WAN communication between a central network and various remote networks or extranet partner networks. However, implementing VPN services in the DMZ has its share of difficulties. For one, you must determine the placement of the VPN tunnel termination point.To identify the location for this device, you must conduct an evaluation as to the security of the device itself. Can it withstand an attack? Are there known vulnerabilities in the software?

Another factor that affects VPN device placement and VPN design is the function of the VPN. More and more companies are turning from dialup services to VPNs for remote access connectivity for telecommuters as well as mobile workers.The prime motivating factor in this move appears to be an overall lower total cost of ownership (TCO) of VPNs compared with dialup phone lines.

It is easy to get confused when we think about all the VPN technologies available, especially since many of them have different functions.To understand these technologies, it helps to step back and look at the basic definition of a VPN, which is just isolated network connectivity over a shared or public network.The word virtual refers to the fact that this connection must pass over a larger shared network as the transport mechanism, whereas the word private describes that this connection only offers connectivity between the endpoints, not the intermediate systems, keeping it isolated from the rest of...