Neutron rejects use of same IP address from different Neutron subnets

Neutron rejects with an "IP address already allocated" error a (valid) attempt to have two ports created with the same IP address, each from a different Neutron subnets.

Eg: following port POST fails:

{
"ports": [
{
"id": "a072db9f-8067-43bc-9691-7f1fc1214699",
"network_id": "7c2dcb47-77c1-4b00-9a0f-1a7b577631a4",
"name": "",
"mac_address": "FA:16:3E:B7:28:75",
"fixed_ips": [

{ "ip_address": "3.0.0.3", "subnet_id": "ca70bf6f-523c-41d8-b5b7-168f83f4b244" }

],
"device_id": "dhcpaa4c2e4c-f328-523c-87fd-16223faf8411-7c2dcb47-77c1-4b00-9a0f-1a7b577631a4",
"device_owner": "network:dhcp",
"tenant_id": "1be0580fefbf4982be6875bd9973a166",
},
{
"id": "8bf4dd31-bdbf-4288-b5dc-ca0a50d3b518",
"network_id": "92695939-e482-4776-930b-07652e63ecaf",
"name": "",
"mac_address": "FA:16:3E:A3:91:20",
"fixed_ips": [

{ "ip_address": "3.0.0.3", "subnet_id": "6f1d7270-f4c3-4b6d-8947-6f691106eaf5" }

],
"device_id": "dhcpaa4c2e4c-f328-523c-87fd-16223faf8411-92695939-e482-4776-930b-07652e63ecaf",
"device_owner": "network:dhcp",
"tenant_id": "1be0580fefbf4982be6875bd9973a166",

}
]

}