Provider network in Installation Guide

I am installing the neutron service in an Ubuntu 20.04. Following the tutorial, I have to create the provider network, but I am receiving the following error:

openstack network create --share --external --provider-physical-network provider --provider-network-type flat provider
Unable to establish connection to http://openstack-controller:9696/v2.0/networks: HTTPConnectionPool(host='openstack-controller', port=9696): Max retries exceeded with url: /v2.0/networks (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x7f017cbf6310>: Failed to establish a new connection: [Errno 111] Connection refused'))

What is wrong once I followed exactly the steps suggested in the tutorial?

Tutorials followed:
https://docs.openstack.org/neutron/wallaby/install/controller-install-option1-ubuntu.html
https://docs.openstack.org/install-guide/launch-instance-networks-provider.html

This bug tracker is for errors with the documentation, use the following as a template and remove or add fields as you see fit. Convert [ ] into [x] to check boxes:

- [X] This doc is inaccurate in this way: The documentation must be updated as it is divided. I was receiving an error when creating the provider network. Then I searched for the problem and saw that someone suggested to run the command to populate the database, which is just at the end of this link https://docs.openstack.org/neutron/wallaby/install/controller-install-ubuntu.html . Also, I had to restart the neutron service, which is just indicated at the end of that link too.
- [ ] This is a doc addition request.
- [ ] I have a fix to the document that I can paste below including example: input and output.

If you have a troubleshooting or support issue, use the following resources:

 - The mailing list: https://lists.openstack.org
 - IRC: 'openstack' channel on OFTC

-----------------------------------
Release: on 2021-07-23 18:07:04
SHA: fbabdbc9ecf36d94d5e6097d613857bdc778bfd4
Source: https://opendev.org/openstack/openstack-manuals/src/doc/install-guide/source/launch-instance-networks-provider.rst
URL: https://docs.openstack.org/install-guide/launch-instance-networks-provider.html