OpenStack basically uses its own neutron layer-2 agent plugin to manage network in clouds. "neutron-openvswitch-agent" is the most common L2 agent which creates an OpenVSwitch (OpenFlow-compatible software switch provided in Linux) on each compute node. When a new instance is created, nova communicates with neutron for network configuration, such as assigning IP address, adding a bridge, creating network tunnel, etc. Neutron-server on the controller node then communicates with neutron-openvswitch-agent on the compute node where the VM will be hosted to actually create a new port and tunnel for the VM.
In order to set up openvswitch-agent as L2 driver, the following configuration should be done in neutron.
1. Controller/Network node
Install:
# yum install openstack-neutron openstack-neutron-openvswitch/etc/neutron/neutron.conf:
.../etc/neutron/plugins/ml2/ml2_conf.ini:
[DEFAULT]
core_plugin=neutron.plugins.ml2.plugin.Ml2Plugin
.../etc/neutron/plugins/ml2/openvswitch.ini
[ml2]
mechanism_drivers =openvswitch
tunnel_bridge = br-tun
local_ip = [LOCAL_IP]
bridge_mappings =extnet:br-ex #br-ex interface should set up manually for external connection
Of course, there are much more configuration in addition to the above settings. In this article, we only care of the difference between OVS and ODL. For more details on how to setup neutron-openvswitch, check out OpenStack guides.
2. Compute node
Install openvswitch-agent:
# yum install openstack-neutron-openvswitch/etc/neutron/plugins/ml2/openvswitch.ini
tunnel_bridge = br-tunAfter all, both controller and compute nodes should have openvswitch-agent which communicates with the controller's neutron server.
local_ip = [LOCAL_IP]
OpenDaylight + OpenStack
Although OpenStack's default openvswitch plugin provides extensive functionality, it does not provide the full SDN functionality that can be brought by OpenFlow switches that connects physical hosts. As this L2 driver can only communicate with OVS in hypervisors, not with switches, it's not possible to manage the network. Also, those OVS in each compute node actually communicates only with its own local SDN controller (neutron-openvswitch-agent running on each node), OVS's are not managed globally by a central controller. Instead, neutron-server in the controller is in charge of managing every neutron-openvswitch-agent in each node which controls the local OVS.
If you want to empower your cloud with full SDN functionality, it's good idea to consider using a separate SDN controller to manage the whole network. OpenDaylight (ODL) is one of popular SDN controller and working closely with OpenStack for integration of ODL with OpenStack.
ODL can be running with OpenStack side by side. In contrast to openvswitch-agent where OVS in compute nodes is connected to the local agent, OVS are all connected to the ODL remotely. In this mode, ODL is functioning as L2 agent, thus the central ODL controller manages all OVS in every compute node. Since OVS is directly connected to ODL, neutron-openvswitch-agent is not necessary any more on all nodes.
In order to use ODL along with OpenStack, a specific L2 driver is necessary to allow OpenStack to communicate with ODL's NorthBound API. ODL and OpenStack team has made 'networking-odl' module in this purpose.
More detailed install instruction can be found in ODL site and OpenStack site.
1. Controller/network node
Uninstall:
# yum uninstall openstack-neutron-openvswitch
Install:
# yum install python-networking-odl
/etc/neutron/neutron.conf
service_plugins = odl-router
/etc/neutron/plugins/ml2/ml2_conf.ini
tenant_network_types=vxlan
mechanism_drivers = opendaylight
port_binding_controller = network-topology
Running agents:
- neutron-dhcp-agent
- neutron-metadata-agent
- neutron-metering-agent
<Note 1>
opendaylight_v2 and odl-route_v2 can be used alternatively, which are for experimental development. For experimental usage, v2 is a good option as all new features are included. For stable usage, v1 is more recommended as you won't find more errors. Remind that these versions should be in pair, e.g. opendaylight_v2 cannot be used with odl-router.
<Note 2>
port_binding_controller setting is to determine how to get host configuration for binding a port. "network-topology" or "pseudo-agentdb-binding" can be used. The former is to use network topology which does not need an extra configuration. The latter is using OVS that contains 'hostconfigs', but it should be set up with "neutron-odl-ovs-hostconfig" command. It's by default "pseudo-agentdb-binding", but you will get error messages like these:
No valid hostconfigs in agentsdb for host
ERROR networking_odl.ml2.pseudo_agentdb_binding KeyError: 'hostconfig'
WARNING networking_odl.ml2.pseudo_agentdb_binding [-] ODL hostconfigs REST/GET failed, will retry on next poll
If so, set up a proper hostconfigs using 'neutron-odl-ovs-hostconfig' or change the 'port_binding_controller' setting.
<Note 3>
Neutron's L3-agent can be replaced by ODL. In such case, disable neutron-l3-agent and enable ODL's L3Fwd feature by changing "ovsdb.l3.fwd.enabled=yes" in ...karaf/etc/custom.properties file.
<Note 4>
In order to install networking-odl, I recommend to use yum instead of pip, as pip can mess up all Python dependencies that creates conflicts with OpenStack. Although the instruction guide recommends pip, it's good to consider yum especially if your other OpenStack components are installed by yum or PackStack. As PackStack uses yum, there will not be any dependency issue.
2. Compute node
Uninstall:
# yum uninstall openstack-neutron-openvswitch
Configuration:
# ovs-vsctl set-manager tcp:${CONTROL_HOST}:6640
Useful commands:
systemctl stop neutron-server
systemctl stop neutron-openvswitch-agent
systemctl stop openvswitch
Some tips...
- ODL(karaf) and networking-odl module is necessary only on controller node. On compute nodes, just change the management server of OVS to indicate ODL.2.
- Don't confuse between openvswitch (OVS) and neutron-openvswitch-agent. OVS is a virtual switch provided by Linux kernel that mimics OpenFlow switch. 'neutron'-openvswitch-agent is the agent software used by OpenStack neutron in order to manage OVS in compute nodes.
- ODL karaf can be run as daemon. Search 'karaf daemon' for instructions.
- As mentioned above, those configurations explained above is a partial instruction missing a lot of information. Please refer to the full instruction guides to install ODL, setting up networking-odl,
