dummy bridge for inter-vm VLAN

gistfile1.txt

create a script like this
( mkdir /usr/local/scripts )
/usr/local/scripts/generate_vmbr20.sh

modprobe -o dummy0 dummy1
ifconfig dummy0 up
brctl addbr vmbr20
brctl addif vmbr20 dummy0
ifconfig vmbr20 up

chmod +x /usr/local/scripts/generate_vmbr20.sh

And add to your vmbr0-section in /etc/network/interfaces

post-up /usr/local/scripts/generate_vmbr20.sh

==========================================
# sample
/etc/network/interfaces


auto vmbr0
iface vmbr0 inet static
    address  x.y.z.41
    netmask  255.255.255.224
    gateway  x.y.z.33
    broadcast  x.y.z.63
    network x.y.z.32
    # dns-* options are implemented by the resolvconf package, if installed
    dns-nameservers 8.8.8.8
    dns-search mydomain.com
    bridge_ports eth0
    bridge_stp off
    bridge_fd 0
    post-up /usr/local/scripts/generate_vmbr20.sh