Comment 2 for bug 1564946

From the stack account on baremetal I can run:

cat external.xml
  <interface type='bridge'>
      <source bridge='brext'/>
      <target dev='tap0'/>
      <model type='virtio'/>
    </interface>

virsh attach-device control_0 external.xml

On the VM I now see:

11: eth1: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN qlen 1000
    link/ether 52:54:00:63:70:56 brd ff:ff:ff:ff:ff:ff

running

sudo ifup eth1

 reports a failure, but afterwards the interface seems to be up