I like emulation/virtualization a lot. I used to use Win4Lin and VMWare for testing new systems/applications I now have switched to VirtualBox mainly because of the automation scripting tools (VBoxManage and friends).
I work/play on a linux laptop and need to run several virtual machines interconnected in an isolated network and the VirtualBox network configuration can give headaches, it gave me some : ) During the setup I had to write things down on paper, walk around chewing my pencil, scratch my head .. so I will share theses notes here hoping it will be usefull to someone.
For a 10000 feet view of the setup explained here, a simple picture is better than many words :
Host->External: independant the virtual network
opt switchable per vbox
VBoxes-->External: virtualbox nat