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SYSTEMD.NET-NAMING-SCHEME(7systemd.net-naming-scheSYSTEMD.NET-NAMING-SCHEME(7)

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
       +-------+----------------------------+
       |Prefix | Description                |
       +-------+----------------------------+
       |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
           +------------------------------------------------------------+--------------------------+
           |Format                                                      | Description              |
           +------------------------------------------------------------+--------------------------+
           |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.

           In some configurations a parent PCI bridge of a given network
           controller may be associated with a slot. In such case we don't
           generate this device property to avoid possible naming conflicts.

       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
           +----------------------------------------------------------------------+---------------------------+
           |Format                                                                | Description               |
           +----------------------------------------------------------------------+---------------------------+
           |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 (which may be chosen
       at system boot-up time via the net.naming-scheme= kernel command line
       switch, see above:

       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).

       v247
           If the PCI slot is assocated with PCI bridge and that has multiple
           child network controllers then all of them might derive the same
           value of ID_NET_NAME_SLOT property. That could cause naming
           conflict if the property is selected as a device name. Now, we
           detect the situation, slot - bridge relation, and we don't produce
           the ID_NET_NAME_SLOT property to avoid possible naming conflict.

       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

systemd 245                                       SYSTEMD.NET-NAMING-SCHEME(7)

NAME | DESCRIPTION | NAMING | HISTORY | EXAMPLES | SEE ALSO | NOTES