You shouldn't be using the router name, try this instead:
router_interface: type: OS::Neutron::RouterInterface properties: router: {get_resource: router} subnet: {get_resource: internal_subnet}
You shouldn't be using the router name, try this instead:
router_interface: :RouterInterfac e
type: OS::Neutron:
properties:
router: {get_resource: router}
subnet: {get_resource: internal_subnet}