Trunking

updated: 2020-07-28 12:10

Trunking¶

The network trunk service allows multiple networks to be connected to an instance using a single virtual NIC (vNIC). Multiple networks can be presented to an instance by connecting it to a single port.

Operation¶

Network trunking consists of a service plug-in and a set of drivers that manage trunks on different layer-2 mechanism drivers. Users can create a port, associate it with a trunk, and launch an instance on that port. Users can dynamically attach and detach additional networks without disrupting operation of the instance.

Every trunk has a parent port and can have any number of subports. The parent port is the port that the trunk is associated with. Users create instances and specify the parent port of the trunk when launching instances attached to a trunk.

The network presented by the subport is the network of the associated port. When creating a subport, a segmentation-id may be required by the driver. segmentation-id defines the segmentation ID on which the subport network is presented to the instance. segmentation-type may be required by certain drivers like OVS, although at this time only vlan is supported as a segmentation-type.

Note

The segmentation-type and segmentation-id parameters are optional in the Networking API. However, all drivers as of the Newton release require both to be provided when adding a subport to a trunk. Future drivers may be implemented without this requirement.

The segmentation-type and segmentation-id specified by the user on the subports is intentionally decoupled from the segmentation-type and ID of the networks. For example, it is possible to configure the Networking service with tenant_network_types = vxlan and still create subports with segmentation_type = vlan. The Networking service performs remapping as necessary.

Example configuration¶

The ML2 plug-in supports trunking with the following mechanism drivers:

Open vSwitch (OVS)
Linux bridge
Open Virtual Network (OVN)

When using a segmentation-type of vlan, the OVS and Linux bridge drivers present the network of the parent port as the untagged VLAN and all subports as tagged VLANs.

Controller node¶

In the neutron.conf file, enable the trunk service plug-in:
```
[DEFAULT]
service_plugins = trunk
```

Verify service operation¶

Source the administrative project credentials and list the enabled extensions.
Use the command openstack extension list --network to verify that the Trunk Extension and Trunk port details extensions are enabled.

Workflow¶

At a high level, the basic steps to launching an instance on a trunk are the following:

Create networks and subnets for the trunk and subports
Create the trunk
Add subports to the trunk
Launch an instance on the trunk

Create networks and subnets for the trunk and subports¶

Create the appropriate networks for the trunk and subports that will be added to the trunk. Create subnets on these networks to ensure the desired layer-3 connectivity over the trunk.

Create the trunk¶

Create a parent port for the trunk.

$ openstack port create --network project-net-A trunk-parent
+-------------------+-------------------------------------------------------------------------+
| Field             | Value                                                                   |
+-------------------+-------------------------------------------------------------------------+
| admin_state_up    | UP                                                                      |
| binding_vif_type  | unbound                                                                 |
| binding_vnic_type | normal                                                                  |
| fixed_ips         | ip_address='192.0.2.7',subnet_id='8b957198-d3cf-4953-8449-ad4e4dd712cc' |
| id                | 73fb9d54-43a7-4bb1-a8dc-569e0e0a0a38                                    |
| mac_address       | fa:16:3e:dd:c4:d1                                                       |
| name              | trunk-parent                                                            |
| network_id        | 1b47d3e7-cda5-48e4-b0c8-d20bd7e35f55                                    |
+-------------------+-------------------------------------------------------------------------+

Create the trunk using --parent-port to reference the port from the previous step:

$ openstack network trunk create --parent-port trunk-parent trunk1
+-----------------+--------------------------------------+
| Field           | Value                                |
+-----------------+--------------------------------------+
| admin_state_up  | UP                                   |
| id              | fdf02fcb-1844-45f1-9d9b-e4c2f522c164 |
| name            | trunk1                               |
| port_id         | 73fb9d54-43a7-4bb1-a8dc-569e0e0a0a38 |
| sub_ports       |                                      |
+-----------------+--------------------------------------+

Add subports to the trunk¶

Subports can be added to a trunk in two ways: creating the trunk with subports or adding subports to an existing trunk.

Create trunk with subports:

This method entails creating the trunk with subports specified at trunk creation.

$ openstack port create --network project-net-A trunk-parent
+-------------------+-------------------------------------------------------------------------+
| Field             | Value                                                                   |
+-------------------+-------------------------------------------------------------------------+
| admin_state_up    | UP                                                                      |
| binding_vif_type  | unbound                                                                 |
| binding_vnic_type | normal                                                                  |
| fixed_ips         | ip_address='192.0.2.7',subnet_id='8b957198-d3cf-4953-8449-ad4e4dd712cc' |
| id                | 73fb9d54-43a7-4bb1-a8dc-569e0e0a0a38                                    |
| mac_address       | fa:16:3e:dd:c4:d1                                                       |
| name              | trunk-parent                                                            |
| network_id        | 1b47d3e7-cda5-48e4-b0c8-d20bd7e35f55                                    |
+-------------------+-------------------------------------------------------------------------+

$ openstack port create --network trunked-net subport1
+-------------------+----------------------------------------------------------------------------+
| Field             | Value                                                                      |
+-------------------+----------------------------------------------------------------------------+
| admin_state_up    | UP                                                                         |
| binding_vif_type  | unbound                                                                    |
| binding_vnic_type | normal                                                                     |
| fixed_ips         | ip_address='198.51.100.8',subnet_id='2a860e2c-922b-437b-a149-b269a8c9b120' |
| id                | 91f9dde8-80a4-4506-b5da-c287feb8f5d8                                       |
| mac_address       | fa:16:3e:ba:f0:4d                                                          |
| name              | subport1                                                                   |
| network_id        | aef78ec5-16e3-4445-b82d-b2b98c6a86d9                                       |
+-------------------+----------------------------------------------------------------------------+

$ openstack network trunk create \
  --parent-port trunk-parent \
  --subport port=subport1,segmentation-type=vlan,segmentation-id=100 \
  trunk1
+----------------+-------------------------------------------------------------------------------------------------+
| Field          | Value                                                                                           |
+----------------+-------------------------------------------------------------------------------------------------+
| admin_state_up | UP                                                                                              |
| id             | 61d8e620-fe3a-4d8f-b9e6-e1b0dea6d9e3                                                            |
| name           | trunk1                                                                                          |
| port_id        | 73fb9d54-43a7-4bb1-a8dc-569e0e0a0a38                                                            |
| sub_ports      | port_id='73fb9d54-43a7-4bb1-a8dc-569e0e0a0a38', segmentation_id='100', segmentation_type='vlan' |
+----------------+-------------------------------------------------------------------------------------------------+

Add subports to an existing trunk:

This method entails creating a trunk, then adding subports to the trunk after it has already been created.

$ openstack network trunk set --subport \
  port=subport1,segmentation-type=vlan,segmentation-id=100 \
  trunk1

Note

The command provides no output.

$ openstack network trunk show trunk1
+----------------+-------------------------------------------------------------------------------------------------+
| Field          | Value                                                                                           |
+----------------+-------------------------------------------------------------------------------------------------+
| admin_state_up | UP                                                                                              |
| id             | 61d8e620-fe3a-4d8f-b9e6-e1b0dea6d9e3                                                            |
| name           | trunk1                                                                                          |
| port_id        | 73fb9d54-43a7-4bb1-a8dc-569e0e0a0a38                                                            |
| sub_ports      | port_id='73fb9d54-43a7-4bb1-a8dc-569e0e0a0a38', segmentation_id='100', segmentation_type='vlan' |
+----------------+-------------------------------------------------------------------------------------------------+

Launch an instance on the trunk¶

Show trunk details to get the port_id of the trunk.

$ openstack network trunk show trunk1
+----------------+--------------------------------------+
| Field          | Value                                |
+----------------+--------------------------------------+
| admin_state_up | UP                                   |
| id             | 61d8e620-fe3a-4d8f-b9e6-e1b0dea6d9e3 |
| name           | trunk                                |
| port_id        | 73fb9d54-43a7-4bb1-a8dc-569e0e0a0a38 |
| sub_ports      |                                      |
+----------------+--------------------------------------+

Launch the instance by specifying port-id using the value of port_id from the trunk details. Launching an instance on a subport is not supported.

Using trunks and subports inside an instance¶

When configuring instances to use a subport, ensure that the interface on the instance is set to use the MAC address assigned to the port by the Networking service. Instances are not made aware of changes made to the trunk after they are active. For example, when a subport with a segmentation-type of vlan is added to a trunk, any operations specific to the instance operating system that allow the instance to send and receive traffic on the new VLAN must be handled outside of the Networking service.

When creating subports, the MAC address of the trunk parent port can be set on the subport. This will allow VLAN subinterfaces inside an instance launched on a trunk to be configured without explicitly setting a MAC address. Although unique MAC addresses can be used for subports, this can present issues with ARP spoof protections and the native OVS firewall driver. If the native OVS firewall driver is to be used, we recommend that the MAC address of the parent port be re-used on all subports.

Trunk states¶

ACTIVE

The trunk is ACTIVE when both the logical and physical resources have been created. This means that all operations within the Networking and Compute services have completed and the trunk is ready for use.
DOWN

A trunk is DOWN when it is first created without an instance launched on it, or when the instance associated with the trunk has been deleted.
DEGRADED

A trunk can be in a DEGRADED state when a temporary failure during the provisioning process is encountered. This includes situations where a subport add or remove operation fails. When in a degraded state, the trunk is still usable and some subports may be usable as well. Operations that cause the trunk to go into a DEGRADED state can be retried to fix temporary failures and move the trunk into an ACTIVE state.
ERROR

A trunk is in ERROR state if the request leads to a conflict or an error that cannot be fixed by retrying the request. The ERROR status can be encountered if the network is not compatible with the trunk configuration or the binding process leads to a persistent failure. When a trunk is in ERROR state, it must be brought to a sane state (ACTIVE), or else requests to add subports will be rejected.
BUILD

A trunk is in BUILD state while the resources associated with the trunk are in the process of being provisioned. Once the trunk and all of the subports have been provisioned successfully, the trunk transitions to ACTIVE. If there was a partial failure, the trunk transitions to DEGRADED.

When admin_state is set to DOWN, the user is blocked from performing operations on the trunk. admin_state is set by the user and should not be used to monitor the health of the trunk.

Limitations and issues¶

See bugs for more information.