Unable to complete operation on subnet One or more ports have an IP allocation from this subnet

root@controller:~# neutron net-list
+--------------------------------------+-------------+-----------------------------------------------------+
| id                                   | name        | subnets                                             |
+--------------------------------------+-------------+-----------------------------------------------------+
| 0d5e24d8-4123-4089-9c03-5072028dc782 | oneseries   |                                                     |
| a7386ebf-bb8f-4831-adb0-d87b49bd581c | provider    | 02d54463-d558-4b78-a081-07a278e52327 192.168.1.0/24 |
| 8a816987-d40d-4823-97a6-bb25bd158d7b | selfservice | eedfde36-bd92-43eb-b570-78eac106b615 10.1.12.192/26 |
|                                      |             | 19f3dab4-2ea8-4385-8c3b-69f47577f935 172.16.1.0/24  |
+--------------------------------------+-------------+-----------------------------------------------------+

When I tried to remove the subnet , I got the below error.

root@controller:~# neutron net-delete selfservice
Unable to complete operation on network 8a816987-d40d-4823-97a6-bb25bd158d7b. There are one or more ports still in use on the network.
Neutron server returns request_ids: ['req-6ba9f812-be4e-4339-91f3-c4ffb25c8ea3']


root@controller:~# neutron subnet-delete selfservice
Unable to complete operation on subnet 19f3dab4-2ea8-4385-8c3b-69f47577f935: One or more ports have an IP allocation from this subnet.
Neutron server returns request_ids: ['req-88bd0673-3041-493d-842b-7ab1b2076108']

root@controller:~# neutron subnet-delete oneseries
Unable to complete operation on subnet eedfde36-bd92-43eb-b570-78eac106b615: One or more ports have an IP allocation from this subnet.
Neutron server returns request_ids: ['req-3be34152-07d8-49f2-81b0-b262978fc198']





 root@controller:~# neutron router-list
+--------------------------------------+--------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------+-------+
| id                                   | name   | external_gateway_info                                                                                                                                                                     | distributed | ha    |
+--------------------------------------+--------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------+-------+
| 7682cdda-f152-4eea-b35b-3a81dd91fd04 | router | {"network_id": "a7386ebf-bb8f-4831-adb0-d87b49bd581c", "enable_snat": true, "external_fixed_ips": [{"subnet_id": "02d54463-d558-4b78-a081-07a278e52327", "ip_address": "192.168.1.102"}]} | False       | False |
+--------------------------------------+--------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------+-------+
root@controller:~# neutron router-gateway-clear router
Removed gateway from router router

root@controller:~# neutron router-interface-delete router oneseries
Removed interface from router router.

root@controller:~# neutron subnet-delete oneseries
Deleted subnet: oneseries

root@controller:~# neutron subnet-list
+--------------------------------------+-------------+----------------+----------------------------------------------------+
| id                                   | name        | cidr           | allocation_pools                                   |
+--------------------------------------+-------------+----------------+----------------------------------------------------+
| 02d54463-d558-4b78-a081-07a278e52327 | provider    | 192.168.1.0/24 | {"start": "192.168.1.101", "end": "192.168.1.200"} |
| 19f3dab4-2ea8-4385-8c3b-69f47577f935 | selfservice | 172.16.1.0/24  | {"start": "172.16.1.2", "end": "172.16.1.254"}     |
+--------------------------------------+-------------+----------------+----------------------------------------------------+

you may notice that the subnet "oneseries" was removed.