Comment 11 for bug 1376446

In fact after doing some more debugging, the bug is not fixed, but OVS is helping to hide it in certain scenarios:

The tap interface for the qlbaas-namespace is created via "ovs-vsctl add-port br-int tap-xxx". Now it seems that the MTU for br-int is automatically lowered to the minimum of the values for the attached interfaced. And the add-port action clones that MTU to the new tap interface. So the trigger for this is simply to boot an instance, that action will set the MTU of br-int to 1450 (which may be a bug in itself, as it will also affect VLAN based networks), and in the sequence all lb instances created after that will have the correct MTU and will no longer be affected by the current bug.