I started with the guide Experimenting with OpenStack Essex on Ubuntu 12.04 LTS under VirtualBox and here are the settings I wound up with in VirtualBox
Under Preferences > Network create a Host-only network called vboxnet0.
vboxnet0 (disable DHCP Server too)
Create a new VM and go to the Network section.
The Adapters for the VM itself.
Network settings in the Ubuntu VM
iface lo inet loopback
# The primary network interface
iface eth0 inet dhcp
#iface eth1 inet static
# Instead of having eth1 in /etc/network/interfaces
# we create directly br100 and attach it to eth1
iface br100 inet static
And in my devstack localrc / local.conf file I've included the following settings:
This will allow to access your instances (when associated to a floating IP) from your host machine
Hope this works for you too!