Stuff should be ran as the user that's running virtualbox or else you won't see any messages.
List nat networks
VBoxManage list natnetworks
For some reason phpvirtualbox doesn't disable dhcp on an host-only if after I've enabled it .. here's how to disable that
VBoxManage dhcpserver remove --ifname vboxnet0
On the clients you'll probably want to install the vbox additions but you'll need these packages first.
# for debian apt-get install build-essential linux-headers-$(uname -r) # for centos yum install gcc make gcc-c++ kernel-devel-$(uname -r)
A nice lil' project I'm using is phpvirtualbox.