Provided by: systemd_245.4-4ubuntu3_amd64 bug

NAME

       systemd.net-naming-scheme - Network device naming schemes

DESCRIPTION

       Network interfaces names and MAC addresses may be generated based on certain stable
       interface attributes. This is possible when there is enough information about the device
       to generate those attributes and the use of this information is configured. This page
       describes interface naming, i.e. what possible names may be generated. Those names are
       generated by the systemd-udevd.service(8) builtin net_id and exported as udev properties
       (ID_NET_NAME_ONBOARD=, ID_NET_LABEL_ONBOARD=, ID_NET_NAME_PATH=, ID_NET_NAME_SLOT=).

       Names and MAC addresses are derived from various stable device metadata attributes. Newer
       versions of udev take more of these attributes into account, improving (and thus possibly
       changing) the names and addresses used for the same devices. Different versions of those
       generation rules are called "naming schemes". The default naming scheme is chosen at
       compilation time. Usually this will be the latest implemented version, but it is also
       possible to set one of the older versions to preserve compatibility. This may be useful
       for example for distributions, which may introduce new versions of systemd in stable
       releases without changing the naming scheme. The naming scheme may also be overridden
       using the net.naming-scheme= kernel command line switch, see systemd-udevd.service(8).
       Available naming schemes are described below.

       After the udev properties have been generated, appropriate udev rules may be used to
       actually rename devices based on those properties. See the description of NamePolicy= and
       MACAddressPolicy= in systemd.link(5).

       Note that while the concept of network interface naming schemes is primarily relevant in
       the context of systemd-udevd.service, the systemd-nspawn(1) container manager also takes
       it into account when naming network interfaces, see below.

NAMING

       All names start with a two-character prefix that signifies the interface type.

       Table 1. Two character prefixes based on the type of interface
       ┌───────┬─────────────────────────────┐
       │PrefixDescription                 │
       ├───────┼─────────────────────────────┤
       │en     │ Ethernet                    │
       ├───────┼─────────────────────────────┤
       │ib     │ InfiniBand                  │
       ├───────┼─────────────────────────────┤
       │sl     │ Serial line IP (slip)       │
       ├───────┼─────────────────────────────┤
       │wl     │ Wireless local area network │
       │       │ (WLAN)                      │
       ├───────┼─────────────────────────────┤
       │ww     │ Wireless wide area network  │
       │       │ (WWAN)                      │
       └───────┴─────────────────────────────┘

       The udev net_id builtin exports the following udev device properties:

       ID_NET_NAME_ONBOARD=prefixonumber
           This name is set based on the numeric ordering information given by the firmware for
           on-board devices. The name consists of the prefix, letter o, and a number specified by
           the firmware. This is only available for PCI devices.

       ID_NET_LABEL_ONBOARD=prefix label
           This property is set based on textual label given by the firmware for on-board
           devices. The name consists of the prefix concatenated with the label. This is only
           available for PCI devices.

       ID_NET_NAME_MAC=prefixxAABBCCDDEEFF
           This name consists of the prefix, letter x, and 12 hexadecimal digits of the MAC
           address. It is available if the device has a fixed MAC address. Because this name is
           based on an attribute of the card itself, it remains "stable" when the device is moved
           (even between machines), but will change when the hardware is replaced.

       ID_NET_NAME_SLOT=prefix[Pdomain]sslot[ffunction][nport_name|ddev_port],
       ID_NET_NAME_SLOT=prefixvslot,
       ID_NET_NAME_SLOT=prefix[Pdomain]sslot[ffunction][nport_name|ddev_port]bnumber,
       ID_NET_NAME_SLOT=prefix[Pdomain]sslot[ffunction][nport_name|ddev_port]uport...[cconfig][iinterface],
       ID_NET_NAME_SLOT=prefix[Pdomain]sslot[ffunction][nport_name|ddev_port]vslot
           This property describes the slot position. Different schemes are used depending on the
           bus type, as described in the table below. In case of USB, BCMA, and SR-VIO devices,
           the full name consists of the prefix, PCI slot identifier, and USB or BCMA or SR-VIO
           slot identifier. The first two parts are denoted as "..." in the table below.

           Table 2. Slot naming schemes
           ┌────────────────────────────────────────────────────────────┬─────────────────────────────────┐
           │FormatDescription                     │
           ├────────────────────────────────────────────────────────────┼─────────────────────────────────┤
           │prefix [Pdomain] sslot [ffunction] [nport_name | ddev_port] │ PCI slot number                 │
           ├────────────────────────────────────────────────────────────┼─────────────────────────────────┤
           │prefix vslot                                                │ VIO slot number (IBM PowerVM)   │
           ├────────────────────────────────────────────────────────────┼─────────────────────────────────┤
           │... bnumber                                                 │ Broadcom bus (BCMA) core number │
           ├────────────────────────────────────────────────────────────┼─────────────────────────────────┤
           │... uport... [cconfig] [iinterface]                         │ USB port number chain           │
           ├────────────────────────────────────────────────────────────┼─────────────────────────────────┤
           │... vslot                                                   │ SR-VIO slot number              │
           └────────────────────────────────────────────────────────────┴─────────────────────────────────┘
           The PCI domain is only prepended when it is not 0. All multi-function PCI devices will
           carry the ffunction number in the device name, including the function 0 device. For
           non-multi-function devices, the number is suppressed if 0. The port name port_name is
           used, or the port number ddev_port if the name is not known.

           For BCMA devices, the core number is suppressed when 0.

           For USB devices the full chain of port numbers of hubs is composed. If the name gets
           longer than the maximum number of 15 characters, the name is not exported. The usual
           USB configuration number 1 and interface number 0 values are suppressed.

           SR-IOV virtual devices are named based on the name of the parent interface, with a
           suffix of v and the virtual device number, with any leading zeros removed. The bus
           number is ignored.

       ID_NET_NAME_PATH=prefixcbus_id, ID_NET_NAME_PATH=prefixavendormodeliinstance,
       ID_NET_NAME_PATH=prefixiaddressnport_name,
       ID_NET_NAME_PATH=prefix[Pdomain]pbussslot[ffunction][nphys_port_name|ddev_port],
       ID_NET_NAME_PATH=prefix[Pdomain]pbussslot[ffunction][nphys_port_name|ddev_port]bnumber,
       ID_NET_NAME_PATH=prefix[Pdomain]pbussslot[ffunction][nphys_port_name|ddev_port]uport...[cconfig][iinterface]
           This property describes the device installation location. Different schemes are used
           depending on the bus type, as described in the table below. For BCMA and USB devices,
           PCI path information must known, and the full name consists of the prefix, PCI slot
           identifier, and USB or BCMA location. The first two parts are denoted as "..." in the
           table below.

           Table 3. Path naming schemes
           ┌──────────────────────────────────────────────────────────────────────┬─────────────────────────────────┐
           │FormatDescription                     │
           ├──────────────────────────────────────────────────────────────────────┼─────────────────────────────────┤
           │prefix cbus_id                                                        │ CCW or grouped CCW device       │
           │                                                                      │ identifier                      │
           ├──────────────────────────────────────────────────────────────────────┼─────────────────────────────────┤
           │prefix avendor model iinstance                                        │ ACPI path names for ARM64       │
           │                                                                      │ platform devices                │
           ├──────────────────────────────────────────────────────────────────────┼─────────────────────────────────┤
           │prefix iaddress nport_name                                            │ Netdevsim (simulated networking │
           │                                                                      │ device) device number and port  │
           │                                                                      │ name                            │
           ├──────────────────────────────────────────────────────────────────────┼─────────────────────────────────┤
           │prefix [Pdomain] pbus sslot [ffunction] [nphys_port_name | ddev_port] │ PCI geographical location       │
           ├──────────────────────────────────────────────────────────────────────┼─────────────────────────────────┤
           │... bnumber                                                           │ Broadcom bus (BCMA) core number │
           ├──────────────────────────────────────────────────────────────────────┼─────────────────────────────────┤
           │... uport... [cconfig] [iinterface]                                   │ USB port number chain           │
           └──────────────────────────────────────────────────────────────────────┴─────────────────────────────────┘
           CCW and grouped CCW devices are found in IBM System Z mainframes. Any leading zeros
           and dots are suppressed.

           For PCI, BCMA, and USB devices, the same rules as described above for slot naming are
           used.

HISTORY

       The following "naming schemes" have been defined:

       v238
           This is the naming scheme that was implemented in systemd 238.

       v239
           Naming was changed for virtual network interfaces created with SR-IOV and NPAR and for
           devices where the PCI network controller device does not have a slot number
           associated.

           SR-IOV virtual devices are named based on the name of the parent interface, with a
           suffix of "vport", where port is the virtual device number. Previously those virtual
           devices were named as if completely independent.

           The ninth and later NPAR virtual devices are named following the scheme used for the
           first eight NPAR partitions. Previously those devices were not renamed and the kernel
           default ("ethN") was used.

           Names are also generated for PCI devices where the PCI network controller device does
           not have an associated slot number itself, but one of its parents does. Previously
           those devices were not renamed and the kernel default was used.

       v240
           The "ib" prefix and stable names for infiniband devices are introduced. Previously
           those devices were not renamed.

           The ACPI index field (used in ID_NET_NAME_ONBOARD=) is now also used when 0.

           A new naming policy NamePolicy=keep was introduced. With this policy, if the network
           device name was already set by userspace, the device will not be renamed again.
           Previously, this naming policy applied implicitly, and now it must be explicitly
           requested. Effectively, this means that network devices will be renamed according to
           the configuration, even if they have been renamed already, if keep is not specified as
           the naming policy in the .link file. See systemd.link(5) for a description of
           NamePolicy=.

       v241
           MACAddressPolicy=persistent was extended to set MAC addresses based on the device
           name. Previously addresses were only based on the ID_NET_NAME_* attributes, which
           meant that interface names would never be generated for virtual devices. Now a
           persistent address will be generated for most devices, including in particular
           bridges.

           Note: when userspace does not set a MAC address for a bridge device, the kernel will
           initially assign a random address, and then change it when the first device is
           enslaved to the bridge. With this naming policy change, bridges get a persistent MAC
           address based on the bridge name instead of the first enslaved device.

       v243
           Support for renaming netdevsim (simulated networking) devices was added. Previously
           those devices were not renamed.

           Previously two-letter interface type prefix was prepended to ID_NET_LABEL_ONBOARD=.
           This is not done anymore.

       v245
           When systemd-nspawn(1) derives the name for the host side of the network interface
           created with --network-veth from the container name it previously simply truncated the
           result at 15 characters if longer (since that's the maximum length for network
           interface names). From now on, for any interface name that would be longer than 15
           characters the last 4 characters are set to a 24bit hash value of the full interface
           name. This way network interface name collisions between multiple similarly named
           containers (who only differ in container name suffix) should be less likely (but still
           possible, since the 24bit hash value is very small).

       Note that latest may be used to denote the latest scheme known (to this particular version
       of systemd.

EXAMPLES

       Example 1. Using udevadm test-builtin to display device properties

           $ udevadm test-builtin net_id /sys/class/net/enp0s31f6
           ...
           Using default interface naming scheme 'v243'.
           ID_NET_NAMING_SCHEME=v243
           ID_NET_NAME_MAC=enx54ee75cb1dc0
           ID_OUI_FROM_DATABASE=Wistron InfoComm(Kunshan)Co.,Ltd.
           ID_NET_NAME_PATH=enp0s31f6
           ...

       Example 2. PCI Ethernet card with firmware index "1"

           ID_NET_NAME_ONBOARD=eno1
           ID_NET_NAME_ONBOARD_LABEL=Ethernet Port 1

       Example 3. PCI Ethernet card in hotplug slot with firmware index number

           # /sys/devices/pci0000:00/0000:00:1c.3/0000:05:00.0/net/ens1
           ID_NET_NAME_MAC=enx000000000466
           ID_NET_NAME_PATH=enp5s0
           ID_NET_NAME_SLOT=ens1

       Example 4. PCI Ethernet multi-function card with 2 ports

           # /sys/devices/pci0000:00/0000:00:1c.0/0000:02:00.0/net/enp2s0f0
           ID_NET_NAME_MAC=enx78e7d1ea46da
           ID_NET_NAME_PATH=enp2s0f0

           # /sys/devices/pci0000:00/0000:00:1c.0/0000:02:00.1/net/enp2s0f1
           ID_NET_NAME_MAC=enx78e7d1ea46dc
           ID_NET_NAME_PATH=enp2s0f1

       Example 5. PCI WLAN card

           # /sys/devices/pci0000:00/0000:00:1c.1/0000:03:00.0/net/wlp3s0
           ID_NET_NAME_MAC=wlx0024d7e31130
           ID_NET_NAME_PATH=wlp3s0

       Example 6. PCI IB host adapter with 2 ports

           # /sys/devices/pci0000:00/0000:00:03.0/0000:15:00.0/net/ibp21s0f0
           ID_NET_NAME_PATH=ibp21s0f0

           # /sys/devices/pci0000:00/0000:00:03.0/0000:15:00.1/net/ibp21s0f1
           ID_NET_NAME_PATH=ibp21s0f1

       Example 7. USB built-in 3G modem

           # /sys/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.4/2-1.4:1.6/net/wwp0s29u1u4i6
           ID_NET_NAME_MAC=wwx028037ec0200
           ID_NET_NAME_PATH=wwp0s29u1u4i6

       Example 8. USB Android phone

           # /sys/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.2/2-1.2:1.0/net/enp0s29u1u2
           ID_NET_NAME_MAC=enxd626b3450fb5
           ID_NET_NAME_PATH=enp0s29u1u2

       Example 9. s390 grouped CCW interface

           # /sys/devices/css0/0.0.0007/0.0.f5f0/group_device/net/encf5f0
           ID_NET_NAME_MAC=enx026d3c00000a
           ID_NET_NAME_PATH=encf5f0

SEE ALSO

       udev(7), udevadm(8), Predictable Network Interface Names[1], systemd-nspawn(1)

NOTES

        1. Predictable Network Interface Names
           https://systemd.io/PREDICTABLE_INTERFACE_NAMES