Instance is unreachable after instance STOP/START operation in Red Hat OpenStack Platform 16.2

Issue

After instance STOP/START operation

• trunk port (parent port and all of the subports) associated to that instance becomes DOWN

  (overcloud) [stack@hostname1 ~]$ openstack port list
  +--------------------------------------+------------------------------------------+-------------------+-----------------------------------------------------------------------------+--------+
  | ID                                   | Name                                     | MAC Address       | Fixed IP Addresses                                                          | Status |
  +--------------------------------------+------------------------------------------+-------------------+-----------------------------------------------------------------------------+--------+
  | aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa | hostname2-parent_port_aaaa-aaaaaaaaaaaa  | 00:00:00:00:00:aa | ip_address='192.0.2.0', subnet_id='aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa'    | DOWN   | < ======== parent port
  | bbbbbbbb-bbbb-bbbb-bbbb-bbbbbbbbbbbb | hostname2-sub_port_bbbb_bbb-bbbbbbbbbbbb | 00:00:00:00:00:bb | ip_address='198.51.100.1', subnet_id='bbbbbbbb-bbbb-bbbb-bbbb-bbbbbbbbbbbb' | DOWN   | < ======== subport
  | cccccccc-cccc-cccc-cccc-cccccccccccc | hostname2-sub_port_cccc_ccc-cccccccccccc | 00:00:00:00:00:cc | ip_address='198.51.100.2', subnet_id='cccccccc-cccc-cccc-cccc-cccccccccccc' | DOWN   | < ======== subport
  | dddddddd-dddd-dddd-dddd-dddddddddddd | hostname2-sub_port_dddd_ddd-dddddddddddd | 00:00:00:00:00:dd | ip_address='198.51.100.3', subnet_id='dddddddd-dddd-dddd-dddd-dddddddddddd' | DOWN   | < ======== subport
  

• as a result, concerned instance bocomes unreachable