libvirt users - Aug 2014 - error configuring a public bridge --> uvt-kvm: error: libvirt domain 'newtest' has no NIC MACs available.

Hi all,

First at all, excuse if this is not the right place for sending this email.
I'm using ubuntu 14.04 server edition and i'm trying to deploy some
virtual
machines in a server in such a way that they are visible in the same
network that the host machine.

The tools I'm using are the uvtool package and libvirt.
The error I'm getting is the following:
"uvt-kvm: error: libvirt domain 'newtest' has no NIC MACs
available."

Here I'm providing the quickest way (I think) of reproducing my problem.
The steps to follow would be:

1) Creating a bridge. This is my /etc/network/interfaces
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

auto em1
iface em1 inet manual

auto br0
iface br0 inet static
  address 9.109.124.62
  network 9.109.124.0
  netmask 255.255.255.0
  broadcast 9.109.124.255
  gateway 9.109.124.1
#iface br0 inet dhcp
  bridge_ports em1
  bridge_stp off
  bridge_fd 0
  bridge_maxwait 0
  dns-search xx.xx.xx.xx
  dns-nameservers 192.168.122.1 9.0.146.50 9.0.148.50

 2) downloading a trusty tahr cloud image and run it
 uvt-simplestreams-libvirt sync release=precise arch=amd64
 uvt-kvm create test release=trusty

 3) duplicate the xml generated when running the machine in order to modify
the network interface by the bridge one. In the XML I also remove the uuid
and change the VM name.
 sudo mv /etc/libvirt/qemu/test.xml  /etc/libvirt/qemu/test2.xml
 In test 2 the most relevant change is replacing

    <interface type='network'>
      <mac address='52:54:00:86:7a:31'/>
      <source network='default'/>
      <model type='virtio'/>
      <address type='pci' domain='0x0000' bus='0x00'
slot='0x03'
function='0x0'/>
    </interface>

by
    <interface type='bridge'>
      <source bridge='br0'/>
      <model type='virtio'/>
    </interface>

 4) Once I have my new XML, I define and start the new machine
  uvt-kvm destroy test
  virsh undefine test
  sudo virsh define  /etc/libvirt/qemu/test2.xml
  virsh start newtest  (newtest is the name provided in test2.xml)

 5) Up to this point everything seems to be fine, but if i run a wait
command i get the error
  uvt-kvm wait newtest --insecure
  uvt-kvm: error: libvirt domain 'newtest' has no NIC MACs available.


I have checked the xml generated when defining newtest and there is a MAC
in there, so it is not a problem generating a MAC address. Also the
interface br0 is visible for virsh:
 virsh iface-list
 Name                 State      MAC Address
---------------------------------------------------
 br0                  active     xx:xx:xx:xx:xx:xx
 lo                   active     00:00:00:00:00:00

 I have been googling for a while and couldn't find anything but this:
 http://pastebin.com/em0hmy4t
 That tries something similar and falls in the same error.

 Any help will be very much appreciated. It is the first time i send
anything to one of this mail lists, so, please, if you need me to provide
any other info, tell me.

 Thanks!

 Jordi