My project aims to connect to systems behind NAT (which are under different public IPs) from outside so that the system under different NAT may have the same private IPs. Here a server program running under one NAT should able to poll client program running under different NAT so that the client program may have the same private IPs. MicrosoftÃ‚Â® WindowsÃ‚Â® 2000 includes extensive support for virtual private networking technology, which leverages the IP connectivity of the Internet to connect remote clients and remote offices. As a network professional, you should understand the important uses of virtual private networking for your organization and the underlying technologies that make it work: Point-to-Point Tunneling Protocol (PPTP), Layer Two Tunneling Protocol (L2TP), virtual private networks and security, virtual private networks and routing and translation, virtual private networks and firewalls, and the troubleshooting of virtual private network connections. You should already be familiar with TCP/IP, IP routing, IP Security (IPSec), and the Windows 2000 remote access server.