Not sure what changed, but without this setting, ND packets would not
get through to other hosts connected to the same bridge.
-<network>
+<network ipv6='yes'>
<name>vnet1</name>
<uuid>1d6ac7c7-60d9-56c1-a7df-210d3d0cc6d1</uuid>
<forward dev='lo' mode='route'>
-<network>
+<network ipv6='yes'>
<name>vnet2</name>
<uuid>b5147a7d-e184-5c9e-3838-4621796ba95c</uuid>
<forward dev='lo' mode='route'>
-<network>
+<network ipv6='yes'>
<name>vnet3</name>
<uuid>5c537abc-c116-90e9-a0ef-886340d4c356</uuid>
<forward dev='lo' mode='route'>