nova/doc/v3/api_samples/os-fixed-ips/v2.4/fixedips-get-resp.json

{
    "fixed_ip": {
        "address": "192.168.1.1",
        "cidr": "192.168.1.0/24",
        "host": "host",
        "hostname": "openstack",
        "reserved": false
    }
}