There are VPN clients for linux. I used Cisco's from my work machine to remote locations. It required adding modules to the kernel, but it has a shell script to do so, so not much is required. Last I checked, you can't download it from them however, unless you have a Cisco contract of some type. You should see what manufacturer made the VPN system you use, and then see if they have a linux client. I would think most VPN systems have linux clients, but some may not.