Error on kubernetes Cluster create "The Parameter (fixed_network_name) was not defined in template."

Hello,

i have installed OpenStack Ussuri via Kolla ansible in a "all in one" Installation on Ubuntu 18.04 including Magnum.

The core Modules are working, i could also define a Cluster Template, but on Cluster Create I get the following Error:

Status
    CREATE_FAILED
Status Reason
    ERROR: The Parameter (fixed_network_name) was not defined in template.

I can not find a Parameter "fixed_network_name" in the cluster Template or the Magnum Docs.

Anyone familiar with that Problem?

This is the output of "openstack coe cluster show":
+----------------------+------------------------------------------------------------------------------------------------------------------------------------------------------+
| Field | Value |
+----------------------+------------------------------------------------------------------------------------------------------------------------------------------------------+
| status | CREATE_FAILED |
| health_status | None |
| cluster_template_id | 17e0cf90-aa46-4deb-94d0-588f51c4425e |
| node_addresses | [] |
| uuid | 1fd23a29-c3d5-418e-b5de-88748be9aed0 |
| stack_id | None |
| status_reason | ERROR: The Parameter (fixed_network_name) was not defined in template. |
| created_at | 2020-10-27T15:28:03+00:00 |
| updated_at | 2020-10-27T15:28:07+00:00 |
| coe_version | None |
| labels | {'kube_dashboard_enabled': '0', 'kube_tag': '1.16.2', 'availability_zone': 'nova', 'auto_scaling_enabled': 'False', 'auto_healing_enabled': 'False'} |
| labels_overridden | {} |
| labels_skipped | {} |
| labels_added | {'availability_zone': 'nova', 'auto_scaling_enabled': 'False', 'auto_healing_enabled': 'False'} |
| fixed_network | None |
| fixed_subnet | None |
| floating_ip_enabled | True |
| faults | {} |
| keypair | mykey |
| api_address | None |
| master_addresses | [] |
| master_lb_enabled | False |
| create_timeout | 60 |
| node_count | 1 |
| discovery_url | https://discovery.etcd.io/bb6df4122b6fb40ac379069c9e8504cd |
| master_count | 1 |
| container_version | None |
| name | test |
| master_flavor_id | m1.small |
| flavor_id | m1.small |
| health_status_reason | {} |
| project_id | 3d5630059f3c4e678eea1a76a94c6f3c |
+----------------------+------------------------------------------------------------------------------------------------------------------------------------------------------+