neutron-lib/api-ref/source/v2/samples/subnets/subnets-create-bulk-request.json

{
    "subnets": [
        {
            "cidr": "192.168.199.0/24",
            "ip_version": 4,
            "network_id": "e6031bc2-901a-4c66-82da-f4c32ed89406"
        },
        {
            "cidr": "10.56.4.0/22",
            "ip_version": 4,
            "network_id": "64239a54-dcc4-4b39-920b-b37c2144effa"
        }
    ]
}