Network segment ranges¶

The network segment range service exposes the segment range management to be administered via the Neutron API. In addition, it introduces the ability for the administrator to control the segment ranges globally or on a per-tenant basis.

Why you need it¶

Before Stein, network segment ranges were configured as an entry in ML2 config file ml2_conf.ini that was statically defined for tenant network allocation and therefore had to be managed as part of the host deployment and management. When a regular tenant user creates a network, Neutron assigns the next free segmentation ID (VLAN ID, VNI etc.) from the configured segment ranges. Only an administrator can assign a specific segment ID via the provider extension.

The network segment range management service provides the following capabilities that the administrator may be interested in:

To check out the network segment ranges defined by the operators in the ML2 config file so that the admin can use this information to make segment range allocation.
To dynamically create and assign network segment ranges, which can help with the distribution of the underlying network connection mapping for privacy or dedicated business connection needs. This includes:
- global shared network segment ranges
- tenant-specific network segment ranges
To dynamically update a network segment range to offer the ability to adapt to the connection mapping changes.
To dynamically manage a network segment range when there are no segment ranges defined within the ML2 config file ml2_conf.ini and no restart of the Neutron server is required in this situation.
To check the availability and usage statistics of network segment ranges.

How it works¶

A network segment range manages a set of segments from which self-service networks can be allocated. The network segment range management service is admin-only.

As a regular project in an OpenStack cloud, you can not create a network segment range of your own and you just create networks in regular way.

If you are an admin, you can create a network segment range which can be shared (i.e. used by any regular project) or tenant-specific (i.e. assignment on a per-tenant basis). Your network segment ranges will not be visible to any other regular projects. Other CRUD operations are also supported.

When a tenant allocates a segment, it will first be allocated from an available segment range assigned to the tenant, and then a shared range if no tenant specific allocation is possible.

Default network segment ranges¶

A set of default network segment ranges are created out of the values defined in the ML2 config file: network_vlan_ranges for ml2_type_vlan, vni_ranges for ml2_type_vxlan, tunnel_id_ranges for ml2_type_gre and vni_ranges for ml2_type_geneve. They will be reloaded when Neutron server starts or restarts. The default network segment ranges are read-only, but will be treated as any other shared ranges on segment allocation.

The administrator can use the default network segment range information to make shared and/or per-tenant range creation and assignment.

Example configuration¶

Controller node¶

Enable the network segment range service plugin by appending network_segment_range to the list of service_plugins in the neutron.conf file on all nodes running the neutron-server service:
```
[DEFAULT]
# ...
service_plugins = ...,network_segment_range,...
```
Restart the neutron-server service.

Verify service operation¶

Source the administrative project credentials and list the enabled extensions.
Use the command openstack extension list --network to verify that the Neutron Network Segment Range extension with Alias network-segment-range is enabled.

$ openstack extension list --network
+-------------------------------+-----------------------+-----------------------------------------------------------+
| Name                          | Alias                 | Description                                               |
+-------------------------------+-----------------------+-----------------------------------------------------------+
| ......                        | ......                | ......                                                    |
+-------------------------------+-----------------------+-----------------------------------------------------------+
| Neutron Network Segment Range | network-segment-range | Provides support for the network segment range management |
+-------------------------------+-----------------------+-----------------------------------------------------------+
| ......                        | ......                | ......                                                    |
+-------------------------------+-----------------------+-----------------------------------------------------------+

Workflow¶

At a high level, the basic workflow for a network segment range creation is the following:

The Cloud administrator:
- Lists the existing network segment ranges.
- Creates a shared or a tenant-specific network segment range based on the requirement.
A regular tenant creates a network in regular way. The network created will automatically allocate a segment from the segment ranges assigned to the tenant or shared if no tenant specific range available.

At a high level, the basic workflow for a network segment range update is the following:

The Cloud administrator:
- Lists the existing network segment ranges and identifies the one that needs to be updated.
- Updates the network segment range based on the requirement.
A regular tenant creates a network in regular way. The network created will automatically allocate a segment from the updated network segment ranges available.

List the network segment ranges or show a network segment range¶

As admin, list the existing network segment ranges:

$ openstack network segment range list
+--------------------------------------+-------------------+---------+--------+----------------------------------+--------------+------------------+------------+------------+
| ID                                   | Name              | Default | Shared | Project ID                       | Network Type | Physical Network | Minimum ID | Maximum ID |
+--------------------------------------+-------------------+---------+--------+----------------------------------+--------------+------------------+------------+------------+
| 20ce94e1-4e51-4aa0-a5f1-26bdfb5bd90e |                   | True    | True   | None                             | vxlan        | None             |          1 |        200 |
| 4b7af684-ec97-422d-ba38-8b9c2919ae67 | test_range_3      | False   | False  | 7011dc7fccac4efda89dc3b7f0d0975a | gre          | None             |        100 |        120 |
| a021e582-6b0f-49f5-90cb-79a670c61973 |                   | True    | True   | None                             | vlan         | default          |          1 |        100 |
| a3373630-969b-4ce9-bae7-dff0f8fa2f92 | test_range_2      | False   | True   | None                             | vxlan        | None             |        501 |        505 |
| a5707a8f-76f0-4f90-9aa7-c42bf54e94b5 |                   | True    | True   | None                             | gre          | None             |          1 |        150 |
| aad1b55b-43f1-46f9-8c35-85f270863ed6 |                   | True    | True   | None                             | geneve       | None             |          1 |        120 |
| e3233178-2866-4f40-b794-7c6fecdc8655 | test_range_1      | False   | False  | 7011dc7fccac4efda89dc3b7f0d0975a | vlan         | group0-data0     |         11 |         11 |
+--------------------------------------+-------------------+---------+--------+----------------------------------+--------------+------------------+------------+------------+

The network segment ranges with Default as True are the ranges specified by the operators in the ML2 config file. Besides, there are also shared and tenant specific network segment ranges created by the admin previously.

The admin is also able to check/show the detailed information (e.g. availability and usage statistics) of a network segment range:

$ openstack network segment range show test_range_1
+------------------+-----------------------------------------------+
| Field            | Value                                         |
+------------------+-----------------------------------------------+
| available        | []                                            |
| default          | False                                         |
| id               | e3233178-2866-4f40-b794-7c6fecdc8655          |
| location         | None                                          |
| maximum          | 11                                            |
| minimum          | 11                                            |
| name             | test_range_1                                  |
| network_type     | vlan                                          |
| physical_network | group0-data0                                  |
| project_id       | 7011dc7fccac4efda89dc3b7f0d0975a              |
| shared           | False                                         |
| used             | {u'7011dc7fccac4efda89dc3b7f0d0975a': ['11']} |
+------------------+-----------------------------------------------+

Create or update the network segment range¶

As admin, create a network segment range based on your requirement:

$ openstack network segment range create --private --project demo \
--network-type vxlan --minimum 120 --maximum 140 test_range_4
+------------------+--------------------------------------+
| Field            | Value                                |
+------------------+--------------------------------------+
| available        | ['120-140']                          |
| default          | False                                |
| id               | c016dcda-5bc3-4e98-b41f-6773e92fcd2d |
| location         | None                                 |
| maximum          | 140                                  |
| minimum          | 120                                  |
| name             | test_range_4                         |
| network_type     | vxlan                                |
| physical_network | None                                 |
| project_id       | 7011dc7fccac4efda89dc3b7f0d0975a     |
| shared           | False                                |
| used             | {}                                   |
+------------------+--------------------------------------+

Update a network segment range based on your requirement:

$ openstack network segment range set --minimum 100 --maximum 150 \
test_range_4

Create a tenant network¶

Now, as project demo (to source the client environment script demo-openrc for demo project according to https://docs.openstack.org/keystone/latest/install/keystone-openrc-rdo.html), create a network in a regular way.

$ source demo-openrc
$ openstack network create test_net
+---------------------------+--------------------------------------+
| Field                     | Value                                |
+---------------------------+--------------------------------------+
| admin_state_up            | UP                                   |
| availability_zone_hints   |                                      |
| availability_zones        |                                      |
| created_at                | 2019-02-25T23:20:36Z                 |
| description               |                                      |
| dns_domain                |                                      |
| id                        | 39e5b95c-ad7a-40b5-9ec1-a4b4a8a43f14 |
| ipv4_address_scope        | None                                 |
| ipv6_address_scope        | None                                 |
| is_default                | False                                |
| is_vlan_transparent       | None                                 |
| location                  | None                                 |
| mtu                       | 1450                                 |
| name                      | test_net                             |
| port_security_enabled     | True                                 |
| project_id                | 7011dc7fccac4efda89dc3b7f0d0975a     |
| provider:network_type     | vxlan                                |
| provider:physical_network | None                                 |
| provider:segmentation_id  | None                                  |
| qos_policy_id             | None                                 |
| revision_number           | 2                                    |
| router:external           | Internal                             |
| segments                  | None                                 |
| shared                    | False                                |
| status                    | ACTIVE                               |
| subnets                   |                                      |
| tags                      |                                      |
| updated_at                | 2019-02-25T23:20:36Z                 |
+---------------------------+--------------------------------------+

Then, switch back to the admin to check the segmentation ID of the tenant network created.

$ source admin-openrc
$ openstack network show test_net
+---------------------------+--------------------------------------+
| Field                     | Value                                |
+---------------------------+--------------------------------------+
| admin_state_up            | UP                                   |
| availability_zone_hints   |                                      |
| availability_zones        |                                      |
| created_at                | 2019-02-25T23:20:36Z                 |
| description               |                                      |
| dns_domain                |                                      |
| id                        | 39e5b95c-ad7a-40b5-9ec1-a4b4a8a43f14 |
| ipv4_address_scope        | None                                 |
| ipv6_address_scope        | None                                 |
| is_default                | False                                |
| is_vlan_transparent       | None                                 |
| location                  | None                                 |
| mtu                       | 1450                                 |
| name                      | test_net                             |
| port_security_enabled     | True                                 |
| project_id                | 7011dc7fccac4efda89dc3b7f0d0975a     |
| provider:network_type     | vxlan                                |
| provider:physical_network | None                                 |
| provider:segmentation_id  | 137                                  |
| qos_policy_id             | None                                 |
| revision_number           | 2                                    |
| router:external           | Internal                             |
| segments                  | None                                 |
| shared                    | False                                |
| status                    | ACTIVE                               |
| subnets                   |                                      |
| tags                      |                                      |
| updated_at                | 2019-02-25T23:20:36Z                 |
+---------------------------+--------------------------------------+

The tenant network created automatically allocates a segment with segmentation ID 137 from the network segment range with segmentation ID range 120-140 that is assigned to the tenant.

If no more available segment in the network segment range assigned to this tenant, then the segment allocation would refer to the shared segment ranges to check whether there’s one segment available. If still there is no segment available, the allocation will fail as follows:

$ openstack network create test_net
$ Unable to create the network. No tenant network is available for
  allocation.

In this case, the admin is advised to check the availability and usage statistics of the related network segment ranges in order to take further actions (e.g. enlarging a segment range etc.).

Known limitations¶

This service plugin is only compatible with ML2 core plugin for now. However, it is possible for other core plugins to support this feature with a follow-on effort.