Description of problem: By default, SNAT is distributed on all of the nodes instead of just the Network nodes. Per: https://opendev.org/openstack/tripleo-heat-templates/src/branch/stable/queens/environments/neutron-ovs-dvr.yaml#L28 Version-Release number of selected component (if applicable): 13.11 How reproducible: Consistently Steps to Reproduce: 1. 2. 3. Actual results: Expected results: Additional info: Customer requests that with the use of composable roles,the default should be a little more dynamic; for example any role running certain compute related services (like nova_libvirt) would get NeutronL3AgentMode: 'dvr' if not specified, rather than hard coding to just a single role (that we expect very few site actually use in production, due to running different physical servers)