In this use case 3, Template directory is "the default core template location (--templates)", isn't it? And the chosen network-isolation.j2.yaml IS located within the custom core templates. Reported by: rhn-engineering-tkuroda https://access.redhat.com/documentation/en-us/red_hat_openstack_platform/16.2/html/advanced_overcloud_customization/assembly_understanding-heat-templates#annotations:337d0c0e-890b-4788-9dcc-673509ab788c