To create a subnet using the OpenStack client, use the subnet create command, as shown here:
The --project argument specifies the ID of the project that the subnet should be associated with and is only available to users with the admin role. This should be the same project associated with the parent network.
The --project-domain argument specifies the ID of the project domain that the subnet should be associated with and is only available to users with the admin role (this is not commonly used).
The --subnet-pool argument specifies the pool from which the subnet will obtain a CIDR.
The --use-default-subnet-pool ...
