Networking Config Version 2

Cloud-init’s support for Version 2 network config is a subset of the version 2 format defined for the netplan tool. Cloud-init supports both reading and writing of Version 2; the latter support requires a distro with netplan present.

Netplan Passthrough

On a system with netplan present, cloud-init will pass Version 2 configuration through to netplan without modification. On such systems, you do not need to limit yourself to the below subset of netplan’s configuration format.

Warning

If you are writing or generating network configuration that may be used on non-netplan systems, you must limit yourself to the subset described in this document, or you will see network configuration failures on non-netplan systems.

Version 2 Configuration Format

The network key has at least two required elements. First it must include version: 2 and one or more of possible device types.

Cloud-init will read this format from system config. For example the following could be present in /etc/cloud/cloud.cfg.d/custom-networking.cfg:

network:
  version: 2
  ethernets: []

It may also be provided in other locations including the NoCloud, see Default Behavior for other places.

Supported device types values are as follows:

  • Ethernets (ethernets)

  • Bonds (bonds)

  • Bridges (bridges)

  • VLANs (vlans)

Each type block contains device definitions as a map where the keys (called “configuration IDs”). Each entry under the types may include IP and/or device configuration.

Device configuration IDs

The key names below the per-device-type definition maps (like ethernets:) are called “ID”s. They must be unique throughout the entire set of configuration files. Their primary purpose is to serve as anchor names for composite devices, for example to enumerate the members of a bridge that is currently being defined.

There are two physically/structurally different classes of device definitions, and the ID field has a different interpretation for each:

Physical devices (Examples: ethernet, wifi):

These can dynamically come and go between reboots and even during runtime (hotplugging). In the generic case, they can be selected by match: rules on desired properties, such as name/name pattern, MAC address, driver, or device paths. In general these will match any number of devices (unless they refer to properties which are unique such as the full path or MAC address), so without further knowledge about the hardware these will always be considered as a group.

It is valid to specify no match rules at all, in which case the ID field is simply the interface name to be matched. This is mostly useful if you want to keep simple cases simple, and it’s how network device configuration has been done for a long time.

If there are match: rules, then the ID field is a purely opaque name which is only being used for references from definitions of compound devices in the config.

Virtual devices (Examples: veth, bridge, bond):

These are fully under the control of the config file(s) and the network stack. I. e. these devices are being created instead of matched. Thus match: and set-name: are not applicable for these, and the ID field is the name of the created virtual device.

Common properties for physical device types

match: <(mapping)>

This selects a subset of available physical devices by various hardware properties. The following configuration will then apply to all matching devices, as soon as they appear. All specified properties must match. The following properties for creating matches are supported:

name: <(scalar)>

Current interface name. Globs are supported, and the primary use case for matching on names, as selecting one fixed name can be more easily achieved with having no match: at all and just using the ID (see above). Note that currently only networkd supports globbing, NetworkManager does not.

macaddress: <(scalar)>

Device’s MAC address in the form xx:xx:xx:xx:xx:xx. Globs are not allowed. Letters must be lowercase.

Note

MAC addresses must be strings. As MAC addresses which consist of only the digits 0-9 (i.e. no hex a-f) can be interpreted as a base 60 integer per the YAML 1.1 spec it is best practice to quote all MAC addresses to ensure they are parsed as strings regardless of value.

driver: <(scalar)>

Kernel driver name, corresponding to the DRIVER udev property. Globs are supported. Matching on driver is only supported with networkd.

Examples:

# all cards on second PCI bus
match:
  name: enp2*

# fixed MAC address
match:
  macaddress: 11:22:33:aa:bb:ff

# first card of driver ``ixgbe``
match:
  driver: ixgbe
  name: en*s0

set-name: <(scalar)>

When matching on unique properties such as path or MAC, or with additional assumptions such as “there will only ever be one wifi device”, match rules can be written so that they only match one device. Then this property can be used to give that device a more specific/desirable/nicer name than the default from udev’s ifnames. Any additional device that satisfies the match rules will then fail to get renamed and keep the original kernel name (and dmesg will show an error).

wakeonlan: <(bool)>

Enable wake on LAN. Off by default.

Common properties for all device types

renderer: <(scalar)>

Use the given networking backend for this definition. Currently supported are networkd and NetworkManager. This property can be specified globally in networks:, for a device type (in e. g. ethernets:) or for a particular device definition. Default is networkd.

Note

Cloud-init only supports networkd backend if rendering version2 config to the instance.

dhcp4: <(bool)>

Enable DHCP for IPv4. Off by default.

dhcp6: <(bool)>

Enable DHCP for IPv6. Off by default.

dhcp4-overrides and dhcp6-overrides: <(mapping)>

DHCP behavior overrides. Overrides will only have an effect if the corresponding DHCP type is enabled. Refer to netplan#dhcp-overrides for more documentation.

Note

These properties are only consumed on netplan and networkd renderers.

The netplan renderer passes through everything and the networkd renderer consumes the following sub-properties:

  • hostname *

  • route-metric *

  • send-hostname *

  • use-dns

  • use-domains

  • use-hostname

  • use-mtu *

  • use-ntp

  • use-routes *

Note

Sub-properties marked with a * are unsupported for dhcp6-overrides when used with the networkd renderer.

Example:

dhcp4-overrides:
  hostname: hal
  route-metric: 1100
  send-hostname: false
  use-dns: false
  use-domains: false
  use-hostname: false
  use-mtu: false
  use-ntp: false
  use-routes: false

addresses: <(sequence of scalars)>

Add static addresses to the interface in addition to the ones received through DHCP or RA. Each sequence entry is in CIDR notation, i. e. of the form addr/prefixlen . addr is an IPv4 or IPv6 address as recognized by inet_pton``(3) and ``prefixlen the number of bits of the subnet.

Example: addresses: [192.168.14.2/24, 2001:1::1/64]

gateway4: or gateway6: <(scalar)>

Set default gateway for IPv4/6, for manual address configuration. This requires setting addresses too. Gateway IPs must be in a form recognized by inet_pton(3)

Example for IPv4: gateway4: 172.16.0.1 Example for IPv6: gateway6: 2001:4::1

mtu: <MTU SizeBytes>

The MTU key represents a device’s Maximum Transmission Unit, the largest size packet or frame, specified in octets (eight-bit bytes), that can be sent in a packet- or frame-based network. Specifying mtu is optional.

nameservers: <(mapping)>

Set DNS servers and search domains, for manual address configuration. There are two supported fields: addresses: is a list of IPv4 or IPv6 addresses similar to gateway*, and search: is a list of search domains.

Example:

nameservers:
  search: [lab, home]
  addresses: [8.8.8.8, FEDC::1]

routes: <(sequence of mapping)>

Add device specific routes. Each mapping includes a to, via key with an IPv4 or IPv6 address as value. metric is an optional value.

Example:

routes:
 - to: 0.0.0.0/0
   via: 10.23.2.1
   metric: 3

Ethernets

Ethernet device definitions do not support any specific properties beyond the common ones described above.

Bonds

interfaces <(sequence of scalars)>

All devices matching this ID list will be added to the bond.

Example:

ethernets:
  switchports:
    match: {name: "enp2*"}
[...]
bonds:
  bond0:
    interfaces: [switchports]

parameters: <(mapping)>

Customization parameters for special bonding options. Time values are specified in seconds unless otherwise specified.

mode: <(scalar)>

Set the bonding mode used for the interfaces. The default is balance-rr (round robin). Possible values are balance-rr, active-backup, balance-xor, broadcast, 802.3ad, balance-tlb, and balance-alb.

lacp-rate: <(scalar)>

Set the rate at which LACPDUs are transmitted. This is only useful in 802.3ad mode. Possible values are slow (30 seconds, default), and fast (every second).

mii-monitor-interval: <(scalar)>

Specifies the interval for MII monitoring (verifying if an interface of the bond has carrier). The default is 0; which disables MII monitoring.

min-links: <(scalar)>

The minimum number of links up in a bond to consider the bond interface to be up.

transmit-hash-policy: <(scalar)>

Specifies the transmit hash policy for the selection of slaves. This is only useful in balance-xor, 802.3ad and balance-tlb modes. Possible values are layer2, layer3+4, layer2+3, encap2+3, and encap3+4.

ad-select: <(scalar)>

Set the aggregation selection mode. Possible values are stable, bandwidth, and count. This option is only used in 802.3ad mode.

all-slaves-active: <(bool)>

If the bond should drop duplicate frames received on inactive ports, set this option to false. If they should be delivered, set this option to true. The default value is false, and is the desirable behavior in most situations.

arp-interval: <(scalar)>

Set the interval value for how frequently ARP link monitoring should happen. The default value is 0, which disables ARP monitoring.

arp-ip-targets: <(sequence of scalars)>

IPs of other hosts on the link which should be sent ARP requests in order to validate that a slave is up. This option is only used when arp-interval is set to a value other than 0. At least one IP address must be given for ARP link monitoring to function. Only IPv4 addresses are supported. You can specify up to 16 IP addresses. The default value is an empty list.

arp-validate: <(scalar)>

Configure how ARP replies are to be validated when using ARP link monitoring. Possible values are none, active, backup, and all.

arp-all-targets: <(scalar)>

Specify whether to use any ARP IP target being up as sufficient for a slave to be considered up; or if all the targets must be up. This is only used for active-backup mode when arp-validate is enabled. Possible values are any and all.

up-delay: <(scalar)>

Specify the delay before enabling a link once the link is physically up. The default value is 0.

down-delay: <(scalar)>

Specify the delay before disabling a link once the link has been lost. The default value is 0.

fail-over-mac-policy: <(scalar)>

Set whether to set all slaves to the same MAC address when adding them to the bond, or how else the system should handle MAC addresses. The possible values are none, active, and follow.

gratuitous-arp: <(scalar)>

Specify how many ARP packets to send after failover. Once a link is up on a new slave, a notification is sent and possibly repeated if this value is set to a number greater than 1. The default value is 1 and valid values are between 1 and 255. This only affects active-backup mode.

packets-per-slave: <(scalar)>

In balance-rr mode, specifies the number of packets to transmit on a slave before switching to the next. When this value is set to 0, slaves are chosen at random. Allowable values are between 0 and 65535. The default value is 1. This setting is only used in balance-rr mode.

primary-reselect-policy: <(scalar)>

Set the reselection policy for the primary slave. On failure of the active slave, the system will use this policy to decide how the new active slave will be chosen and how recovery will be handled. The possible values are always, better, and failure.

learn-packet-interval: <(scalar)>

Specify the interval between sending learning packets to each slave. The value range is between 1 and 0x7fffffff. The default value is 1. This option only affects balance-tlb and balance-alb modes.

Bridges

interfaces: <(sequence of scalars)>

All devices matching this ID list will be added to the bridge.

Example:

ethernets:
  switchports:
    match: {name: "enp2*"}
[...]
bridges:
  br0:
    interfaces: [switchports]

parameters: <(mapping)>

Customization parameters for special bridging options. Time values are specified in seconds unless otherwise specified.

ageing-time: <(scalar)>

Set the period of time to keep a MAC address in the forwarding database after a packet is received.

priority: <(scalar)>

Set the priority value for the bridge. This value should be an number between 0 and 65535. Lower values mean higher priority. The bridge with the higher priority will be elected as the root bridge.

forward-delay: <(scalar)>

Specify the period of time the bridge will remain in Listening and Learning states before getting to the Forwarding state. This value should be set in seconds for the systemd backend, and in milliseconds for the NetworkManager backend.

hello-time: <(scalar)>

Specify the interval between two hello packets being sent out from the root and designated bridges. Hello packets communicate information about the network topology.

max-age: <(scalar)>

Set the maximum age of a hello packet. If the last hello packet is older than that value, the bridge will attempt to become the root bridge.

path-cost: <(scalar)>

Set the cost of a path on the bridge. Faster interfaces should have a lower cost. This allows a finer control on the network topology so that the fastest paths are available whenever possible.

stp: <(bool)>

Define whether the bridge should use Spanning Tree Protocol. The default value is “true”, which means that Spanning Tree should be used.

VLANs

id: <(scalar)>

VLAN ID, a number between 0 and 4094.

link: <(scalar)>

ID of the underlying device definition on which this VLAN gets created.

Example:

ethernets:
  eno1: {...}
vlans:
  en-intra:
    id: 1
    link: eno1
    dhcp4: yes
  en-vpn:
    id: 2
    link: eno1
    address: ...

Examples

Configure an ethernet device with networkd, identified by its name, and enable DHCP:

network:
  version: 2
  ethernets:
    eno1:
      dhcp4: true

This is a complex example which shows most available features:

network:
  version: 2
  ethernets:
    # opaque ID for physical interfaces, only referred to by other stanzas
    id0:
      match:
        macaddress: '00:11:22:33:44:55'
      wakeonlan: true
      dhcp4: true
      addresses:
        - 192.168.14.2/24
        - 2001:1::1/64
      gateway4: 192.168.14.1
      gateway6: 2001:1::2
      nameservers:
        search: [foo.local, bar.local]
        addresses: [8.8.8.8]
      # static routes
      routes:
        - to: 192.0.2.0/24
          via: 11.0.0.1
          metric: 3
    lom:
      match:
        driver: ixgbe
      # you are responsible for setting tight enough match rules
      # that only match one device if you use set-name
      set-name: lom1
      dhcp6: true
    switchports:
      # all cards on second PCI bus; unconfigured by themselves, will be added
      # to br0 below
      match:
        name: enp2*
      mtu: 1280
  bonds:
    bond0:
      interfaces: [id0, lom]
  bridges:
    # the key name is the name for virtual (created) interfaces; no match: and
    # set-name: allowed
    br0:
      # IDs of the components; switchports expands into multiple interfaces
      interfaces: [wlp1s0, switchports]
      dhcp4: true
  vlans:
    en-intra:
      id: 1
      link: id0
      dhcp4: yes