Configuration

In order to use this mechanism driver the Neutron configuration file needs to be created/updated with the appropriate configuration information.

Switch configuration format:

[genericswitch:<switch name>]
device_type = <netmiko device type>
ngs_mac_address = <switch mac address>
ip = <IP address of switch>
port = <ssh port>
username = <credential username>
password = <credential password>
key_file = <ssh key file>
secret = <enable secret>

# If set ngs_port_default_vlan to default_vlan, switch's
# interface will restore the default_vlan.
ngs_port_default_vlan = <port default vlan>

The device_type entry is mandatory. Most other configuration entries are optional, see below.

Note

Switch will be selected by local_link_connection/switch_info or ngs_mac_address. So, you can use the switch MAC address to identify switches if local_link_connection/switch_info is not set.

Examples

These example device configuration snippets are assumed to be part to a specific file /etc/neutron/plugins/ml2/ml2_conf_genericswitch.ini, but they could also be added directly to /etc/neutron/plugins/ml2/ml2_conf.ini.

Here is an example for the Cisco 300 series device:

[genericswitch:sw-hostname]
device_type = netmiko_cisco_s300
ngs_mac_address = <switch mac address>
username = admin
password = password
ip = <switch mgmt ip address>

for the Cisco IOS device:

[genericswitch:sw-hostname]
device_type = netmiko_cisco_ios
ngs_mac_address = <switch mac address>
username = admin
password = password
secret = secret
ip = <switch mgmt ip address>

for the Cisco NX-OS device:

[genericswitch:sw-hostname]
device_type = netmiko_cisco_nxos
ngs_mac_address = <switch mac address>
ip = <switch mgmt ip address>
username = admin
password = password
secret = secret

for the Huawei VRPV3 or VRPV5 device:

[genericswitch:sw-hostname]
device_type = netmiko_huawei
ngs_mac_address = <switch mac address>
username = admin
password = password
port = 8222
secret = secret
ip = <switch mgmt ip address>

for the Huawei VRPV8 device:

[genericswitch:sw-hostname]
device_type = netmiko_huawei_vrpv8
ngs_mac_address = <switch mac address>
username = admin
password = password
port = 8222
secret = secret
ip = <switch mgmt ip address>

for the Arista EOS device:

[genericswitch:arista-hostname]
device_type = netmiko_arista_eos
ngs_mac_address = <switch mac address>
ip = <switch mgmt ip address>
username = admin
key_file = /opt/data/arista_key

for the Dell Force10 device:

[genericswitch:dell-hostname]
device_type = netmiko_dell_force10
ngs_mac_address = <switch mac address>
ip = <switch mgmt ip address>
username = admin
password = password
secret = secret

for the Dell OS10 device:

[genericswitch:dell-hostname]
device_type = netmiko_dell_os10
ngs_mac_address = <switch mac address>
ip = <switch mgmt ip address>
username = admin
password = password
secret = secret

for the Dell PowerConnect device:

[genericswitch:dell-hostname]
device_type = netmiko_dell_powerconnect
ip = <switch mgmt ip address>
username = admin
password = password
secret = secret

# You can set ngs_switchport_mode according to switchmode you have set on
# the switch. The following options are supported: general, access. It
# will default to access mode if left unset. In general mode, the port
# be set to transmit untagged packets.
ngs_switchport_mode = access

Dell PowerConnect devices have been seen to have issues with multiple concurrent configuration sessions. See Synchronization and Batching for details on how to limit the number of concurrent active connections to each device.

for the Brocade FastIron (ICX) device:

[genericswitch:hostname-for-fast-iron]
device_type = netmiko_brocade_fastiron
ngs_mac_address = <switch mac address>
ip = <switch mgmt ip address>
username = admin
password = password

for the Ruijie device:

[genericswitch:sw-hostname]
device_type = netmiko_ruijie
ngs_mac_address = <switch mac address>
username = admin
password = password
secret = secret
ip = <switch mgmt ip address>

for the HPE 5900 Series device:

[genericswitch:sw-hostname]
device_type = netmiko_hp_comware
username = admin
password = password
ip = <switch mgmt ip address>

for the Juniper Junos OS device:

[genericswitch:hostname-for-juniper]
device_type = netmiko_juniper
ip = <switch mgmt ip address>
username = admin
password = password
ngs_commit_timeout = <optional commit timeout (seconds)>
ngs_commit_interval = <optional commit interval (seconds)>

for a Cumulus Linux device:

[genericswitch:hostname-for-cumulus]
device_type = netmiko_cumulus
ip = <switch mgmt_ip address>
username = admin
password = password
secret = secret
ngs_mac_address = <switch mac address>

for the Nokia SRL series device:

[genericswitch:sw-hostname]
device_type = netmiko_nokia_srl
username = admin
password = password
ip = <switch mgmt ip address>

for a Pluribus switch:

[genericswitch:sw-hostname]
device_type = netmiko_pluribus
username = admin
password = password
ip = <switch mgmt ip address>

for an ArubaOS-CX switch:

[genericswitch:aruba-hostname]
device_type = netmiko_aruba_os
username = admin
password = password
ip = <switch mgmt ip address>

General configuration

Additionally the GenericSwitch mechanism driver needs to be enabled from the ml2 config file /etc/neutron/plugins/ml2/ml2_conf.ini:

[ml2]
tenant_network_types = vlan
type_drivers = local,flat,vlan,gre,vxlan
mechanism_drivers = openvswitch,genericswitch
...

Physical networks need to be declared in the ML2 config as well, with a range of VLANs that can be allocated to tenant networks. Several physical networks can coexist, possibly with overlapping VLAN ranges: in that case, each switch configuration needs to include its physical network, see Multiple physical networks. Example of /etc/neutron/plugins/ml2/ml2_conf.ini with two physical networks:

[ml2_type_vlan]
network_vlan_ranges = physnet1:700:799,physnet2:600:850

For a given physical network, it is possible to specify several disjoint ranges of VLANs by simply repeating the physical network name multiple times:

[ml2_type_vlan]
network_vlan_ranges = physnet1:700:720,physnet1:750:760

(Re)start neutron-server specifying the additional configuration file containing switch configuration:

neutron-server \
    --config-file /etc/neutron/neutron.conf \
    --config-file /etc/neutron/plugins/ml2/ml2_conf.ini \
    --config-file /etc/neutron/plugins/ml2/ml2_conf_genericswitch.ini

Synchronization

Some devices are limited in the number of concurrent SSH sessions that they can support, or do not support concurrent configuration database updates. In these cases it can be useful to use an external service to synchronize access to the managed devices. This synchronization is provided by the Tooz library, which provides support for a number of different backends, including Etcd, ZooKeeper, and others. A connection URL for the backend should be configured as follows:

[ngs_coordination]
backend_url = <backend URL>

The backend URL format includes the Tooz driver as the scheme, with driver options passed using query string parameters. For example, to use the etcd3gw driver with an API version of v3 and a path to a CA certificate:

[ngs_coordination]
backend_url = etcd3+https://etcd.example.com?api_version=v3,ca_cert=/path/to/ca/cert.crt

The default behaviour is to limit the number of concurrent active connections to each device to one, but the number may be configured per-device as follows:

[genericswitch:device-hostname]
ngs_max_connections = <max connections>

When synchronization is used, each Neutron thread executing the networking-generic-switch plugin will attempt to acquire a lock, with a default timeout of 60 seconds before failing. This timeout can be configured as follows (setting it to 0 means no timeout):

[ngs_coordination]
...
acquire_timeout = <timeout in seconds>

Batching

For many network devices there is a significant SSH connection overhead which is incurred for each network or port configuration change. In a large scale system with many concurrent changes, this overhead adds up quickly. Since the Antelope release, the Generic Switch driver includes support to batch up switch configuration changes and apply them together using a single SSH connection.

This is implemented using etcd as a queueing system. Commands are added to an input key, then a worker thread processes the available commands for a particular switch device. We pull off the queue using the version at which the keys were added, giving a FIFO style queue. The result of each command set are added to an output key, which the original request thread is watching. Distributed locks are used to serialise the processing of commands for each switch device.

The etcd endpoint is configured using the same [ngs_coordination] backend_url option used in Synchronization, with the limitation that only etcd3gw is supported.

Additionally, each device that will use batched configuration should include the following option:

[genericswitch:device-hostname]
ngs_batch_requests = True

Disabling Inactive Ports

By default, switch interfaces remain administratively enabled when not in use, and the access VLAN association is removed. On most devices, this will cause the interface to be a member of the default VLAN, usually VLAN 1. This could be a security issue, with unallocated ports having access to a shared network.

To resolve this issue, it is possible to configure interfaces as administratively down when not in use. This is done on a per-device basis, using the ngs_disable_inactive_ports flag:

[genericswitch:device-hostname]
ngs_disable_inactive_ports = <optional boolean>

This is currently supported by the following devices:

• Juniper Junos OS

• ArubaOS-CX

• Cisco NX-OS

Network Name Format

By default, when a network is created on a switch, if the switch supports assigning names to VLANs, they are assigned a name of the neutron network UUID. For example:

8f60256e4b6343bf873026036606ce5e

It is possible to use a different format for the network name using the ngs_network_name_format option. This option uses Python string formatting syntax, and accepts the parameters {network_id} and {segmentation_id}. For example:

[genericswitch:device-hostname]
ngs_network_name_format = neutron-{network_id}-{segmentation_id}

Some switches have issues assigning VLANs a name that starts with a number, and this configuration option can be used to avoid this.

Manage VLANs

By default, on network creation VLANs are added to all switches. In a similar way, VLANs are removed when it seems they are no longer required. However, in some cases only a subset of the ports are managed by Neutron. In a similar way, when multiple switches are used, it is very common that the network administrator restricts the VLANs allowed. In these cases, there is little utility in adding and removing vlans on the switches. This process takes time, so not doing this can speed up a number of common operations. A particular case where this can cause problems is when a VLAN used for the switch management interface, or any other port not managed by Neutron, is removed by this Neutron driver.

To stop networking generic switch trying to add or remove VLANs on the switch, administrator are expected to pre-add all enabled VLANs as well as tagging these VLANs on trunk ports. Once those VLANs and trunk ports are preconfigured on the switch, you can use the following configuration to stop networking generic switch adding or removing any VLANs:

[genericswitch:device-hostname]
ngs_manage_vlans = False

Saving configuration on devices

By default, all configuration changes are saved on persistent storage of the devices, using model-specific commands. This occurs after each change.

This may be undesirable for performance reasons, or if you have external means of saving configuration on a regular basis. In this case, configuration saving can be disabled:

[genericswitch:device-hostname]
ngs_save_configuration = False

Trunk ports

When VLANs are created on the switches, it is common to want to tag these VLANS on one or more trunk ports. To do this, you need to declare a comma-separated list of trunk ports that can be managed by Networking Generic Switch. It will then dynamically tag and untag VLANs on these ports whenever it creates and deletes VLANs. For example:

[genericswitch:device-hostname]
ngs_trunk_ports = Ethernet1/48, Port-channel1

This is useful when managing several switches in the same physical network, because they are likely to be interconnected with trunk links. Another important use-case is to connect the DHCP agent with a trunk port, because the agent needs access to all active VLANs.

Note that this option is only used if ngs_manage_vlans = True.

Multiple physical networks

It is possible to use Networking Generic Switch to manage several physical networks. The desired physical network is selected by the Neutron API client when it creates the network object.

In this case, you may want to only create VLANs on switches that belong to the requested physical network, especially because VLAN ranges from separate physical networks may overlap. This also improves reconfiguration performance because fewer switches will need to be configured whenever a network is created/deleted.

To this end, each switch can be configured with a list of physical networks it belongs to:

[genericswitch:device-hostname]
ngs_physical_networks = physnet1, physnet2

Physical network names should match the names defined in the ML2 configuration.

If no physical network is declared in a switch configuration, then VLANs for all physical networks will be created on this switch.

Note that this option is only used if ngs_manage_vlans = True.

SSH algorithm configuration

You may need to tune the SSH negotiation process for some devices. Reasons include using a faster key exchange algorithm, disabling an algorithm that has a buggy implementation on the target device, or working around limitations related to FIPS requirements.

The ngs_ssh_disabled_algorithms configuration parameter allows to selectively disable algorithms of a given type (key exchange, cipher, MAC, etc). It is based on Paramiko’s disabled_algorithms setting.

The format is a list of <type>:<algorithm> entries to disable. The same type can be repeated several times with different algorithms. Here is an example configuration:

[genericswitch:device-hostname]
ngs_ssh_disabled_algorithms = kex:diffie-hellman-group-exchange-sha1, ciphers:blowfish-cbc, ciphers:3des-cbc

As of Paramiko 2.9.1, the valid types are ciphers, macs, keys, pubkeys, kex, gsskex. However, this might change depending on the version of Paramiko. Check Paramiko source code or documentation to determine the accepted algorithm types.