SYSTEMD.NET-NAMING-SCHEME(7systemd.net-naming-scheSYSTEMD.NET-NAMING-SCHEME(7)
NAME
systemd.net-naming-scheme - Network device naming schemes
DESCRIPTION
Network interfaces may be renamed to give them predictable names when
there's enough information to generate appropriate names and the use of
certain types of names is configured. This page describes the first
part, 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 are derived from various device metadata attributes. Newer
versions of udev take more of these attributes into account, improving
(and thus possibly changing) the names used for the same devices.
Differents version of the naming 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 overriden using the net.naming-scheme= kernel
command line switch, see systemd-udevd.service(8). Available naming
schemes are described below.
After the udev proprties have been generated, appropriate udev rules
may be used to actually rename devices based on those properties. See
the description of NamePolicy= in systemd.link(5).
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 |
+-------+----------------------------+
|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 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 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=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
all cases, PCI slot information must be known. 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 |
+------------------------------------------------------------+--------------------------+
|... 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 [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:
rhel-8.0
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.
rhel-8.1
Same as naming scheme rhel-8.0.
rhel-8.2
Same as naming scheme rhel-8.0.
rhel-8.3
Same as naming scheme rhel-8.0.
rhel-8.4
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.
rhel-8.5
Same as naming scheme rhel-8.4.
rhel-8.6
Same as naming scheme rhel-8.4.
rhel-8.7
PCI hotplug slot names for the s390 PCI driver are a hexadecimal
representation of the function_id device attribute. This attribute
is now used to build the ID_NET_NAME_SLOT. Before that, all slot
names were parsed as decimal numbers, which could either result in
an incorrect value of the ID_NET_NAME_SLOT property or none at all.
Some firmware and hypervisor implementations report unreasonable
high numbers for the onboard index. To prevent the generation of
bogus onbard interface names, index numbers greater than 16381
(2^14-1) were ignored. For s390 PCI devices index values up to
65535 (2^16-1) are valid. To account for that, the limit is
increased to now 65535.
rhel-8.8
Same as naming scheme rhel-8.7.
rhel-8.9
Same as naming scheme rhel-8.7.
rhel-8.10
Same as naming scheme rhel-8.7.
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 'rhel-8.3'.
ID_NET_NAMING_SCHEME=rhel-8.3
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=enEthernet 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. 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 7. 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 8. 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), the original page describing stable interface
names[1]
NOTES
1. the original page describing stable interface names
https://www.freedesktop.org/wiki/Software/systemd/PredictableNetworkInterfaceNames
systemd 239 SYSTEMD.NET-NAMING-SCHEME(7)
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