From original issue:

"Description of problem:

Load Balancing Service (Octavia) availability zones (AZ) requires network resources like networks, subnets and routers for AZs. Those resources can be provisioned by octavia-dcn-deployment.yaml. But the ansible playbook does not support to create IPv6 subnet.
https://opendev.org/openstack/tripleo-ansible/src/branch/stable/wallaby/tripleo_ansible/roles/octavia_overcloud_dcn_config/tasks/main.yaml#L25-L32

The non-AZ lb-mgmt-net has already supported IPv6 with bz2057921.

Version-Release number of selected component (if applicable):
17.1

How reproducible:
Always

Steps to Reproduce:
1. Prepare octavia-dcn-parameters.yaml with IPv6 subnet.
2. Run octavia-dcn-deployment.yaml
3.

Actual results:
Fail to create IPv6 subnet

Expected results:
All AZ network resources including IPv6 subnet should be created

Additional info:"

For 18.0 and beyond however, the solution will likely look quite different.