overcloud deployment fails with Failed to bind port <uuid> on host <uuid> for vnic_type baremetal using segments

Issue

• Overcloud deployment fails. The deployment had come up properly. This is after undercloud upgrade following chapter 3.1

• MTU of the ctlplane network was initially set to 9000 but this was corrected to 1500.

• After correcting the MTU from 9000 to 1500, the existing overcloud was deleted and a new attempt was made but the new nodes were getting stuck in spawning:

(undercloud) [root@undercloud ~]# nova list
+--------------------------------------+------------------------+--------+------------+-------------+----------------------+
| ID                                   | Name                   | Status | Task State | Power State | Networks             |
+--------------------------------------+------------------------+--------+------------+-------------+----------------------+
| fca1b2e4-5642-4920-b590-f0543c99bdeb | overcloud-compute-0    | BUILD  | spawning   | NOSTATE     | ctlplane=172.31.0.28 |
| 31ec01a4-1a0e-45f1-b913-e8ab1265f7e3 | overcloud-controller-0 | BUILD  | spawning   | NOSTATE     | ctlplane=172.31.0.7  |
+--------------------------------------+------------------------+--------+------------+-------------+----------------------+

• The following error is seen in /var/log/ironic/ironic-conductor.log:

Jun 11 19:26:30 undercloud ironic-conductor[4210]: 2019-06-11 19:26:30.231 4210 ERROR ironic.drivers.modules.deploy_utils [req-0c8f777b-fba6-45c7-b3b4-7942a4d1a667 - - - - -] Failed to login to an iSCSI target due to iSCSI connection was not seen by the file system after attempting to verify 3 times.: InstanceDeployFailure: iSCSI connection was not seen by the file system after attempting to verify 3 times.
Jun 11 19:26:30 undercloud ironic-conductor[4210]: 2019-06-11 19:26:30.247 4210 ERROR ironic.drivers.modules.deploy_utils [req-7ccdd60f-5ae8-4bd5-ae58-1abe40516a03 - - - - -] Failed to login to an iSCSI target due to iSCSI connection was not seen by the file system after attempting to verify 3 times.: InstanceDeployFailure: iSCSI connection was not seen by the file system after attempting to verify 3 times.
Jun 11 19:26:30 undercloud ironic-conductor[4210]: 2019-06-11 19:26:30.276 4210 ERROR ironic.drivers.modules.deploy_utils [req-3b56e42b-7450-4e99-82b7-2f8832041693 - - - - -] Failed to login to an iSCSI target due to iSCSI connection was not seen by the file system after attempting to verify 3 times.: InstanceDeployFailure: iSCSI connection was not seen by the file system after attempting to verify 3 times.