Comment 1 for bug 1838487

First I create a network and a subnet. network_id=0c557c5f-acf6-44c4-8c1c-cc12672d4d4f
second I update subnet with allocation_pools=[]

then I call api /v2.0/network-ip-availabilities/0c557c5f-acf6-44c4-8c1c-cc12672d4d4f
api return:
{"network_ip_availability": {"used_ips": 1, "subnet_ip_availability": [{"used_ips": 1, "subnet_id": "a5b694f7-7054-4ecc-8447-8e9a7a15c5f0", "subnet_name": "ZhNet-Subnet", "ip_version": 4, "cidr": "192.168.120.0/24", "total_ips": 256}], "network_id": "0c557c5f-acf6-44c4-8c1c-cc12672d4d4f", "tenant_id": "2fb75a1bedac449d904f71fbea5cd1d2", "total_ips": 256, "project_id": "2fb75a1bedac449d904f71fbea5cd1d2", "network_name": "ZhNet"}}
this result tell me: I have 256 available IPs in subnet. but I couldn't create a port successfully in this network.