If you have an inexpensive IPsec VPN endpoint router and want to connect to the LAN behind it while you're on the road, you'll need to use a VPN client. Microsoft has included an IPsec client in Win 2000 and XP, but it is not the most intuitive thing to configure, and many have given up trying in frustration.
Contrary to what you may read in the forums and newsgroups, Microsoft's IPsec client can be made to work! This article will show you how to get it up and running so you can be tunneling away in no time!
Figure 1 shows the network configuration that I'll be using as an example. It uses all private IP addresses, so you should be able to set it up and try it without having to be actually connected to the Internet.
Figure 1: VPN Test setup
This procedure uses a Linksys BEFSX41 as the VPN endpoint router which handles two IPsec tunnels, but should also work with Linksys' BEFVP41, which supports 70 IPsec tunnels. You don't have to use these Linksys routers and could use any other router with built-in VPN endpoint. But many other inexpensive VPN endpoint routers have tunnel throughput in the 400 - 800kbps range vs. the SX41's 2.5Mbps - a limitation you'd definitely notice.