Currently OpenStack-Helm supports OpenVSwitch and LinuxBridge as a network virtualization engines. In order to support many possible backends (SDNs), modular architecture of Neutron chart was developed. OpenStack-Helm can support every SDN solution that has Neutron plugin, either core_plugin or mechanism_driver.

The Neutron reference architecture provides mechanism_drivers OpenVSwitch (OVS) and linuxbridge (LB) with ML2 core_plugin framework.

Other networking services provided by Neutron are:

  1. L3 routing - creation of routers

  2. DHCP - auto-assign IP address and DNS info

  3. Metadata - Provide proxy for Nova metadata service

Introducing a new SDN solution should consider how the above services are provided. It maybe required to disable built-in Neutron functionality.

Neutron architecture

Neutron chart includes the following services:


neutron-server is serving the networking REST API for operator and other OpenStack services usage. The internals of Neutron are highly flexible, providing plugin mechanisms for all networking services exposed. The consistent API is exposed to the user, but the internal implementation is up to the chosen SDN.

Typical networking API request is an operation of create/update/delete:
  • network

  • subnet

  • port

To use other Neutron reference architecture types of SDN, these options should be configured in neutron.conf:

# core_plugin - plugin responsible for L2 connectivity and IP address
#               assignments.
# ML2 (Modular Layer 2) is the core plugin provided by Neutron ref arch
# If other SDN implements its own logic for L2, it should replace the
# ml2 here
core_plugin = ml2

# service_plugins - a list of extra services exposed by Neutron API.
# Example: router, qos, trunk, metering.
# If other SDN implement L3 or other services, it should be configured
# here
service_plugins = router

All of the above configs are endpoints or path to the specific class implementing the interface. You can see the endpoints to class mapping in setup.cfg.

If the SDN of your choice is using the ML2 core plugin, then the extra options in neutron/ml2/plugins/ml2_conf.ini should be configured:

# type_drivers - layer 2 technologies that ML2 plugin supports.
# Those are local,flat,vlan,gre,vxlan,geneve
type_drivers = flat,vlan,vxlan

# mech_drivers - implementation of above L2 technologies. This option is
# pointing to the engines like linux bridge or OpenVSwitch in ref arch.
# This is the place where SDN implementing ML2 driver should be configured
mech_drivers = openvswitch, l2population

SDNs implementing ML2 driver can add extra/plugin-specific configuration options in neutron/ml2/plugins/ml2_conf.ini. Or define its own ml2_conf_<name>.ini file where configs specific to the SDN would be placed.

The above configuration options are handled by neutron/values.yaml:

      # core_plugin can be: ml2, calico
      core_plugin: ml2
      # service_plugin can be: router, odl-router, empty for calico,
      # networking_ovn.l3.l3_ovn.OVNL3RouterPlugin for OVN
      service_plugins: router

        # mechnism_drivers can be: openvswitch, linuxbridge,
        # opendaylight, ovn
        mechanism_drivers: openvswitch,l2population
        type_drivers: flat,vlan,vxlan

Neutron-server service is scheduled on nodes with openstack-control-plane=enabled label.


DHCP agent is running dnsmasq process which is serving the IP assignment and DNS info. DHCP agent is dependent on the L2 agent wiring the interface. So one should be aware that when changing the L2 agent, it also needs to be changed in the DHCP agent. The configuration of the DHCP agent includes option interface_driver, which will instruct how the tap interface created for serving the request should be wired.

      # we can define here, which driver we are using:
      # openvswitch or linuxbridge
      interface_driver: openvswitch

Another place where the DHCP agent is dependent on L2 agent is the dependency for the L2 agent daemonset:

            # this should be set to corresponding neutron L2 agent
            - requireSameNode: true
                application: neutron
                component: neutron-ovs-agent

There is also a need for DHCP agent to pass ovs agent config file (in neutron/templates/bin/

exec neutron-dhcp-agent \
      --config-file /etc/neutron/neutron.conf \
      --config-file /etc/neutron/dhcp_agent.ini \
      --config-file /etc/neutron/metadata_agent.ini \
      --config-file /etc/neutron/plugins/ml2/ml2_conf.ini
{{- if ( has "openvswitch" ) }} \
      --config-file /etc/neutron/plugins/ml2/openvswitch_agent.ini
{{- end }}

This requirement is OVS specific, the ovsdb_connection string is defined in openvswitch_agent.ini file, specifying how DHCP agent can connect to ovs. When using other SDNs, running the DHCP agent may not be required. When the SDN solution is addressing the IP assignments in another way, neutron’s DHCP agent should be disabled.

neutron-dhcp-agent service is scheduled to run on nodes with the label openstack-control-plane=enabled.


L3 agent is serving the routing capabilities for Neutron networks. It is also dependent on the L2 agent wiring the tap interface for the routers.

All dependencies described in neutron-dhcp-agent are valid here.

If the SDN implements its own version of L3 networking, neutron-l3-agent should not be started.

neutron-l3-agent service is scheduled to run on nodes with the label openstack-control-plane=enabled.


Metadata-agent is a proxy to nova-metadata service. This one provides information about public IP, hostname, ssh keys, and any tenant specific information. The same dependencies apply for metadata as it is for DHCP and L3 agents. Other SDNs may require to force the config driver in nova, since the metadata service is not exposed by it.

neutron-metadata-agent service is scheduled to run on nodes with the label openstack-control-plane=enabled.

Configuring network plugin

To be able to configure multiple networking plugins inside of OpenStack-Helm, a new configuration option is added:

  # provide what type of network wiring will be used
  # possible options: openvswitch, linuxbridge, sriov
    - openvswitch

This option will allow to configure the Neutron services in proper way, by checking what is the actual backed set in neutron/values.yaml.

In order to meet modularity criteria of Neutron chart, section manifests in neutron/values.yaml contains boolean values describing which Neutron’s Kubernetes resources should be deployed:

  configmap_bin: true
  configmap_etc: true
  daemonset_dhcp_agent: true
  daemonset_l3_agent: true
  daemonset_lb_agent: false
  daemonset_metadata_agent: true
  daemonset_ovs_agent: true
  daemonset_sriov_agent: true
  deployment_server: true
  ingress_server: true
  job_bootstrap: true
  job_db_init: true
  job_db_sync: true
  job_db_drop: false
  job_image_repo_sync: true
  job_ks_endpoints: true
  job_ks_service: true
  job_ks_user: true
  job_rabbit_init: true
  pdb_server: true
  pod_rally_test: true
  secret_db: true
  secret_keystone: true
  secret_rabbitmq: true
  service_ingress_server: true
  service_server: true

If .Values.manifests.daemonset_ovs_agent will be set to false, neutron ovs agent would not be launched. In that matter, other type of L2 or L3 agent on compute node can be run.

To enable new SDN solution, there should be separate chart created, which would handle the deployment of service, setting up the database and any related networking functionality that SDN is providing.


The ovs set of daemonsets are running on the node labeled openvswitch=enabled. This includes the compute and controller/network nodes. For more flexibility, OpenVSwitch as a tool was split out of Neutron chart, and put in separate chart dedicated OpenVSwitch. Neutron OVS agent remains in Neutron chart. Splitting out the OpenVSwitch creates possibilities to use it with different SDNs, adjusting the configuration accordingly.


As part of Neutron chart, this daemonset is running Neutron OVS agent. It is dependent on having openvswitch-db and openvswitch-vswitchd deployed and ready. Since its the default choice of the networking backend, all configuration is in place in neutron/values.yaml. neutron-ovs-agent should not be deployed when another SDN is used in network.backend.

Script in neutron/templates/bin/ is responsible for determining the tunnel interface and its IP for later usage by neutron-ovs-agent. The IP is set in init container and shared between init container and main container with neutron-ovs-agent via file /tmp/pod-shared/ml2-local-ip.ini.

Configuration of OVS bridges can be done via neutron/templates/bin/ The script is configuring the external network bridge and sets up any bridge mappings defined in conf.auto_bridge_add. These values should align with conf.plugins.openvswitch_agent.ovs.bridge_mappings.

openvswitch-db and openvswitch-vswitchd

This runs the OVS tool and database. OpenVSwitch chart is not Neutron specific, it may be used with other technologies that are leveraging the OVS technology, such as OVN or ODL.

A detail worth mentioning is that ovs is configured to use sockets, rather than the default loopback mechanism.

exec /usr/sbin/ovs-vswitchd unix:${OVS_SOCKET} \
        -vconsole:emer \
        -vconsole:err \
        -vconsole:info \
        --pidfile=${OVS_PID} \


Linuxbridge is the second type of Neutron reference architecture L2 agent. It is running on nodes labeled linuxbridge=enabled. As mentioned before, all nodes that are requiring the L2 services need to be labeled with linuxbridge. This includes both the compute and controller/network nodes. It is not possible to label the same node with both openvswitch and linuxbridge (or any other network virtualization technology) at the same time.


This daemonset includes the linuxbridge Neutron agent with bridge-utils and ebtables utilities installed. This is all that is needed, since linuxbridge uses native kernel libraries.

neutron/templates/bin/ is configuring the tunnel IP, external bridge and all bridge mappings defined in config. It is done in init container, and the IP for tunneling is shared using file /tmp/pod-shared/ml2-local-ip.ini with main linuxbridge container.

In order to use linuxbridge in your OpenStack-Helm deployment, you need to label the compute and controller/network nodes with linuxbridge=enabled and use this neutron/values.yaml override:

  backend: linuxbridge
            - requireSameNode: true
                application: neutron
                component: neutron-lb-agent
            - requireSameNode: true
                application: neutron
                component: neutron-lb-agent
            - requireSameNode: true
                application: neutron
                component: neutron-lb-agent
          pod: null
      interface_driver: linuxbridge
      interface_driver: linuxbridge
      interface_driver: linuxbridge

Other SDNs

In order to add support for more SDNs, these steps need to be performed:

  1. Configure neutron-server with SDN specific core_plugin/mechanism_drivers.

  2. If required, add new networking agent label type.

  3. Specify if new SDN would like to use existing services from Neutron: L3, DHCP, metadata.

  4. Create separate chart with new SDN deployment method.

Nova config dependency

Whenever we change the L2 agent, it should be reflected in nova/values.yaml in dependency resolution for nova-compute.