to configure host networking of Virtualbox

1. install bridge-utils to be able to create network bridges

$ apt-get install bridge-utils

2. back up the current interfaces file

$ cp /etc/network/interfaces /etc/network/interfaces.backup

3. edit /etc/network/interfaces

for static ip address,

auto eth0
iface eth0 inet manual

auto br0
iface br0 inet static
 address 192.168.0.100
 netmask 255.255.255.0
 gateway 192.168.0.1
 bridge_ports eth0 vbox0 vbox1

# The loopback network interface
auto lo


for dynamic address,

auto eth0
iface eth0 inet manual

auto br0
iface br0 inet dhcp
bridge_ports eth0 vbox0

# The loopback network interface
auto lo
iface lo inet loopback


3. restart networking

$ /etc/init.d/networking restart

4. declare virtual interfaces

$ vi /etc/vbox/interfaces
# Each line should be of the format :
# [interface name] [user name] [bridge]
vbox0 [user name] br0
vbox1 [user name] br0
...

for VirtualBox OSE
$ /etc/init.d/virtualbox-ose restart

for pre-compiled proprietary version
$ /etc/init.d/vboxnet restart

5. set permission on /dev/net/tun

$ chown root:vboxusers /dev/net/tun
$ chmod g+rw /dev/net/tun

6. This file is created with the default permissions every time the system
restarts, edit the file /etc/udev/rules.d/20-names.rules to make the new permissions permanent

KERNEL=="tun",   NAME="net/%k"

to

KERNEL=="tun",   NAME="net/%k",   GROUP="vboxusers",   MODE="0660"