For example
tempest.scenario.test_network_v6.TestGettingAddress.test_dualnet_multi_prefix_slaac test time outs when waiting for the server (vm managed by openstack)  receive the IPv6 address.

Version-Release number of selected component (if applicable):
openstack-neutron.noarch           1:11.0.2-0.20171020230401.el7ost
openstack-neutron-common.noarch    1:11.0.2-0.20171020230401.el7ost
openstack-neutron-lbaas.noarch     1:11.0.2-0.20170927152439.743c1db.el7ost
openstack-neutron-lbaas-ui.noarch  3.0.1-2.el7ost      @rhos-12.0-signed        
openstack-neutron-linuxbridge.noarch
openstack-neutron-metering-agent.noarch
openstack-neutron-ml2.noarch       1:11.0.2-0.20171020230401.el7ost
openstack-neutron-openvswitch.noarch
openstack-neutron-sriov-nic-agent.noarch
puppet-neutron.noarch              11.3.1-0.20171005205442.83e8ac7.el7ost
python-neutron.noarch              1:11.0.2-0.20171020230401.el7ost
python-neutron-lbaas.noarch        1:11.0.2-0.20170927152439.743c1db.el7ost
python-neutron-lib.noarch          1.9.1-0.20170821170222.0ef54c3.el7ost
python-neutronclient.noarch        6.5.0-0.20170814170137.355983d.el7ost

2017-10-24.4


Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/tempest/common/utils/__init__.py", line 89, in wrapper
    return f(self, *func_args, **func_kwargs)
  File "/usr/lib/python2.7/site-packages/tempest/scenario/test_network_v6.py", line 258, in test_dualnet_multi_prefix_slaac
    dualnet=True)
  File "/usr/lib/python2.7/site-packages/tempest/scenario/test_network_v6.py", line 193, in _prepare_and_test
    CONF.validation.ping_timeout, 1))
  File "/usr/lib/python2.7/site-packages/unittest2/case.py", line 678, in assertTrue
    raise self.failureException(msg)
AssertionError: False is not true

How reproducible:
Not always