2 <!DOCTYPE refentry PUBLIC
"-//OASIS//DTD DocBook XML V4.5//EN"
3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
4 <!-- SPDX-License-Identifier: LGPL-2.1+ -->
6 <refentry id=
"systemd.net-naming-scheme">
8 <title>systemd.net-naming-scheme
</title>
9 <productname>systemd
</productname>
13 <refentrytitle>systemd.net-naming-scheme
</refentrytitle>
14 <manvolnum>7</manvolnum>
18 <refname>systemd.net-naming-scheme
</refname>
19 <refpurpose>Network device naming schemes
</refpurpose>
23 <title>Description
</title>
25 <para>Network interfaces names and MAC addresses may be generated based on certain stable interface
26 attributes. This is possible when there is enough information about the device to generate those
27 attributes and the use of this information is configured. This page describes interface naming, i.e. what
28 possible names may be generated. Those names are generated by the
29 <citerefentry><refentrytitle>systemd-udevd.service
</refentrytitle><manvolnum>8</manvolnum></citerefentry>
30 builtin
<command>net_id
</command> and exported as udev properties
31 (
<varname>ID_NET_NAME_ONBOARD=
</varname>,
<varname>ID_NET_LABEL_ONBOARD=
</varname>,
32 <varname>ID_NET_NAME_PATH=
</varname>,
<varname>ID_NET_NAME_SLOT=
</varname>).
</para>
34 <para>Names and MAC addresses are derived from various stable device metadata attributes. Newer versions
35 of udev take more of these attributes into account, improving (and thus possibly changing) the names and
36 addresses used for the same devices. Different versions of those generation rules are called
"naming
37 schemes". The default naming scheme is chosen at compilation time. Usually this will be the latest
38 implemented version, but it is also possible to set one of the older versions to preserve
39 compatibility. This may be useful for example for distributions, which may introduce new versions of
40 systemd in stable releases without changing the naming scheme. The naming scheme may also be overridden
41 using the
<varname>net.naming-scheme=
</varname> kernel command line switch, see
42 <citerefentry><refentrytitle>systemd-udevd.service
</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
43 Available naming schemes are described below.
</para>
45 <para>After the udev properties have been generated, appropriate udev rules may be used to actually rename
46 devices based on those properties. See the description of
<varname>NamePolicy=
</varname> and
47 <varname>MACAddressPolicy=
</varname> in
48 <citerefentry><refentrytitle>systemd.link
</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
</para>
54 <para>All names start with a two-character prefix that signifies the interface type.
</para>
57 <title>Two character prefixes based on the type of interface
</title>
63 <entry>Description
</entry>
68 <entry><constant>en
</constant></entry>
69 <entry>Ethernet
</entry>
72 <entry><constant>ib
</constant></entry>
73 <entry>InfiniBand
</entry>
76 <entry><constant>sl
</constant></entry>
77 <entry>serial line IP (slip)
</entry>
80 <entry><constant>wl
</constant></entry>
81 <entry>Wireless local area network (WLAN)
</entry>
84 <entry><constant>ww
</constant></entry>
85 <entry>Wireless wide area network (WWAN)
</entry>
91 <para>The udev
<command>net_id
</command> builtin exports the following udev device properties:
</para>
95 <term><varname>ID_NET_NAME_ONBOARD=
<replaceable>prefix
</replaceable><constant>o
</constant><replaceable>number
</replaceable></varname></term>
97 <listitem><para>This name is set based on the ordering information given by the firmware for
98 on-board devices. The name consists of the prefix, letter
<constant>o
</constant>, and a number
99 specified by the firmware. This is only available for PCI devices.
</para>
104 <term><varname>ID_NET_LABEL_ONBOARD=
<replaceable>prefix
</replaceable> <replaceable>label
</replaceable></varname></term>
106 <listitem><para>This property is set based on label given by the firmware for on-board devices. The
107 name consists of the prefix concatenated with the label. This is only available for PCI devices.
113 <term><varname>ID_NET_NAME_MAC=
<replaceable>prefix
</replaceable><constant>x
</constant><replaceable>AABBCCDDEEFF
</replaceable></varname></term>
115 <listitem><para>This name consists of the prefix, letter
<constant>x
</constant>, and
12 hexadecimal
116 digits of the MAC address. It is available if the device has a fixed MAC address. Because this name
117 is based on an attribute of the card itself, it remains
"stable" when the device is moved (even
118 between machines), but will change when the hardware is replaced.
</para>
123 <term><varname>ID_NET_NAME_SLOT=
<replaceable>prefix
</replaceable>[
<constant>P
</constant><replaceable>domain
</replaceable>]
<constant>s
</constant><replaceable>slot
</replaceable>[
<constant>f
</constant><replaceable>function
</replaceable>][
<constant>n
</constant><replaceable>port_name
</replaceable>|
<constant>d
</constant><replaceable>dev_port
</replaceable>]
</varname></term>
124 <term><varname>ID_NET_NAME_SLOT=
<replaceable>prefix
</replaceable>[
<constant>P
</constant><replaceable>domain
</replaceable>]
<constant>s
</constant><replaceable>slot
</replaceable>[
<constant>f
</constant><replaceable>function
</replaceable>][
<constant>n
</constant><replaceable>port_name
</replaceable>|
<constant>d
</constant><replaceable>dev_port
</replaceable>]
<constant>b
</constant><replaceable>number
</replaceable></varname></term>
125 <term><varname>ID_NET_NAME_SLOT=
<replaceable>prefix
</replaceable>[
<constant>P
</constant><replaceable>domain
</replaceable>]
<constant>s
</constant><replaceable>slot
</replaceable>[
<constant>f
</constant><replaceable>function
</replaceable>][
<constant>n
</constant><replaceable>port_name
</replaceable>|
<constant>d
</constant><replaceable>dev_port
</replaceable>]
<constant>u
</constant><replaceable>port
</replaceable>…[
<constant>c
</constant><replaceable>config
</replaceable>][
<constant>i
</constant><replaceable>interface
</replaceable>]
</varname></term>
126 <term><varname>ID_NET_NAME_SLOT=
<replaceable>prefix
</replaceable>[
<constant>P
</constant><replaceable>domain
</replaceable>]
<constant>s
</constant><replaceable>slot
</replaceable>[
<constant>f
</constant><replaceable>function
</replaceable>][
<constant>n
</constant><replaceable>port_name
</replaceable>|
<constant>d
</constant><replaceable>dev_port
</replaceable>]
<constant>v
</constant><replaceable>slot
</replaceable></varname></term>
128 <listitem><para>This property describes the slot position. Different schemes are used depending on
129 the bus type, as described in the table below. In all cases, PCI slot information must be known. In
130 case of USB, BCMA, and SR-VIO devices, the full name consists of the prefix, PCI slot identifier,
131 and USB or BCMA or SR-VIO slot identifier. The first two parts are denoted as
"…" in the table
135 <title>Slot naming schemes
</title>
140 <entry>Format
</entry>
141 <entry>Description
</entry>
147 <entry><replaceable>prefix
</replaceable> [
<constant>P
</constant><replaceable>domain
</replaceable>]
<constant>s
</constant><replaceable>slot
</replaceable> [
<constant>f
</constant><replaceable>function
</replaceable>] [
<constant>n
</constant><replaceable>port_name
</replaceable> |
<constant>d
</constant><replaceable>dev_port
</replaceable>]
</entry>
148 <entry>PCI slot number
</entry>
152 <entry>…
<constant>b
</constant><replaceable>number
</replaceable></entry>
153 <entry>Broadcom bus (BCMA) core number
</entry>
157 <entry>…
<constant>u
</constant><replaceable>port
</replaceable>… [
<constant>c
</constant><replaceable>config
</replaceable>] [
<constant>i
</constant><replaceable>interface
</replaceable>]
</entry>
158 <entry>USB port number chain
</entry>
162 <entry>…
<constant>v
</constant><replaceable>slot
</replaceable></entry>
163 <entry>SR-VIO slot number
</entry>
169 <para>The PCI domain is only prepended when it is not
0. All multi-function PCI devices will carry
170 the
<constant>f
<replaceable>function
</replaceable></constant> number in the device name, including
171 the function
0 device. For non-multi-function devices, the number is suppressed if
0. The port name
172 <replaceable>port_name
</replaceable> is used, or the port number
173 <constant>d
</constant><replaceable>dev_port
</replaceable> if the name is not known.
</para>
175 <para>For BCMA devices, the core number is suppressed when
0.
</para>
177 <para>For USB devices the full chain of port numbers of hubs is composed. If the name gets longer
178 than the maximum number of
15 characters, the name is not exported. The usual USB configuration
179 number
1 and interface number
0 values are suppressed.
</para>
182 <para>SR-IOV virtual devices are named based on the name of the parent interface, with a suffix of
183 <constant>v
</constant> and the virtual device number, with any leading zeros removed. The bus
184 number is ignored. This device type is found in IBM PowerVMs.
</para>
188 <term><varname>ID_NET_NAME_PATH=
<replaceable>prefix
</replaceable><constant>c
</constant><replaceable>bus_id
</replaceable></varname></term>
189 <term><varname>ID_NET_NAME_PATH=
<replaceable>prefix
</replaceable><constant>a
</constant><replaceable>vendor
</replaceable><replaceable>model
</replaceable><constant>i
</constant><replaceable>instance
</replaceable></varname></term>
190 <term><varname>ID_NET_NAME_PATH=
<replaceable>prefix
</replaceable><constant>i
</constant><replaceable>address
</replaceable><constant>n
</constant><replaceable>port_name
</replaceable></varname></term>
191 <term><varname>ID_NET_NAME_PATH=
<replaceable>prefix
</replaceable>[
<constant>P
</constant><replaceable>domain
</replaceable>]
<constant>p
</constant><replaceable>bus
</replaceable><constant>s
</constant><replaceable>slot
</replaceable>[
<constant>f
</constant><replaceable>function
</replaceable>][
<constant>n
</constant><replaceable>phys_port_name
</replaceable>|
<constant>d
</constant><replaceable>dev_port
</replaceable>]
</varname></term>
192 <term><varname>ID_NET_NAME_PATH=
<replaceable>prefix
</replaceable>[
<constant>P
</constant><replaceable>domain
</replaceable>]
<constant>p
</constant><replaceable>bus
</replaceable><constant>s
</constant><replaceable>slot
</replaceable>[
<constant>f
</constant><replaceable>function
</replaceable>][
<constant>n
</constant><replaceable>phys_port_name
</replaceable>|
<constant>d
</constant><replaceable>dev_port
</replaceable>]
<constant>b
</constant><replaceable>number
</replaceable></varname></term>
193 <term><varname>ID_NET_NAME_PATH=
<replaceable>prefix
</replaceable>[
<constant>P
</constant><replaceable>domain
</replaceable>]
<constant>p
</constant><replaceable>bus
</replaceable><constant>s
</constant><replaceable>slot
</replaceable>[
<constant>f
</constant><replaceable>function
</replaceable>][
<constant>n
</constant><replaceable>phys_port_name
</replaceable>|
<constant>d
</constant><replaceable>dev_port
</replaceable>]
<constant>u
</constant><replaceable>port
</replaceable>…[
<constant>c
</constant><replaceable>config
</replaceable>][
<constant>i
</constant><replaceable>interface
</replaceable>]
</varname></term>
195 <listitem><para>This property describes the device installation location. Different schemes are
196 used depending on the bus type, as described in the table below. For BCMA and USB devices, PCI path
197 information must known, and the full name consists of the prefix, PCI slot identifier, and USB or
198 BCMA location. The first two parts are denoted as
"…" in the table below.
</para>
201 <title>Path naming schemes
</title>
206 <entry>Format
</entry>
207 <entry>Description
</entry>
213 <entry><replaceable>prefix
</replaceable> <constant>c
</constant><replaceable>bus_id
</replaceable></entry>
214 <entry>CCW or grouped CCW device identifier
</entry>
218 <entry><replaceable>prefix
</replaceable> <constant>a
</constant><replaceable>vendor
</replaceable> <replaceable>model
</replaceable> <constant>i
</constant><replaceable>instance
</replaceable></entry>
219 <entry>ACPI path names for ARM64 platform devices
</entry>
223 <entry><replaceable>prefix
</replaceable> <constant>i
</constant><replaceable>address
</replaceable> <constant>n
</constant><replaceable>port_name
</replaceable></entry>
224 <entry>Netdevsim (simulated networking device) device number and port name
</entry>
228 <entry><replaceable>prefix
</replaceable> [
<constant>P
</constant><replaceable>domain
</replaceable>]
<constant>p
</constant><replaceable>bus
</replaceable> <constant>s
</constant><replaceable>slot
</replaceable> [
<constant>f
</constant><replaceable>function
</replaceable>] [
<constant>n
</constant><replaceable>phys_port_name
</replaceable> |
<constant>d
</constant><replaceable>dev_port
</replaceable>]
</entry>
229 <entry>PCI geographical location
</entry>
233 <entry>…
<constant>b
</constant><replaceable>number
</replaceable></entry>
234 <entry>Broadcom bus (BCMA) core number
</entry>
238 <entry>…
<constant>u
</constant><replaceable>port
</replaceable>… [
<constant>c
</constant><replaceable>config
</replaceable>] [
<constant>i
</constant><replaceable>interface
</replaceable>]
</entry>
239 <entry>USB port number chain
</entry>
246 <para>CCW and grouped CCW devices are found in IBM System Z mainframes. Any leading zeros and
247 dots are suppressed.
</para>
249 <para>For PCI, BCMA, and USB devices, the same rules as described above for slot naming are
257 <title>History
</title>
259 <para>The following
"naming schemes" have been defined:
</para>
263 <term><constant>v238
</constant></term>
265 <listitem><para>This is the naming naming that was implemented in systemd
238.
</para></listitem>
269 <term><constant>v239
</constant></term>
271 <listitem><para>Naming was changed for virtual network interfaces created with SR-IOV and NPAR and
272 for devices where the PCI network controller device does not have a slot number associated.
</para>
274 <para>SR-IOV virtual devices are named based on the name of the parent interface, with a suffix of
275 <literal>v
<replaceable>port
</replaceable></literal>, where
<replaceable>port
</replaceable> is the
276 virtual device number. Previously those virtual devices were named as if completely independent.
279 <para>The ninth and later NPAR virtual devices are named following the scheme used for the first
280 eight NPAR partitions. Previously those devices were not renamed and the kernel default
281 (
"eth<replaceable>N</replaceable>") was used.
</para>
283 <para>Names are also generated for PCI devices where the PCI network controller device does not
284 have an associated slot number itself, but one of its parents does. Previously those devices were
285 not renamed and the kernel default was used.
</para>
290 <term><constant>v240
</constant></term>
292 <listitem><para>The
<literal>ib
</literal> prefix and stable names for infiniband devices are
293 introduced. Previously those devices were not renamed.
</para>
295 <para>The ACPI index field (used in
<varname>ID_NET_NAME_ONBOARD=
</varname>) is now also used when
298 <para>A new naming policy
<varname>NamePolicy=keep
</varname> was introduced. With this policy, if
299 the network device name was already set by userspace, the device will not be renamed
300 again. Previously, this naming policy applied implicitly, and now it must be explicitly
301 requested. Effectively, this means that network devices will be renamed according to the
302 configuration, even if they have been renamed already, if
<constant>keep
</constant> is not
303 specified as the naming policy in the
<filename index=
"false">.link
</filename> file. See
304 <citerefentry><refentrytitle>systemd.link
</refentrytitle><manvolnum>5</manvolnum></citerefentry>
305 for a description of
<varname>NamePolicy=
</varname>.
</para></listitem>
309 <term><constant>v241
</constant></term>
311 <listitem><para><option>MACAddressPolicy=persistent
</option> was extended to set MAC addresses
312 based on the device name. Previously addresses were only based on the
313 <varname index=
"false">ID_NET_NAME_*
</varname> attributes, which meant that interface names would
314 never be generated for virtual devices. Now a persistent address will be generated for most
315 devices, including in particular bridges.
</para>
317 <para>Note: when userspace does not set a MAC address for a bridge device, the kernel will
318 initially assign a random address, and then change it when the first device is enslaved to the
319 bridge. With this naming policy change, bridges get a persistent MAC address based on the bridge
320 name instead of the first enslaved device.
</para></listitem>
324 <term><constant>v243
</constant></term>
326 <listitem><para>Support for renaming netdevsim (simulated networking) devices was added. Previously
327 those devices were not renamed.
</para>
329 <para>Previously two-letter interface type prefix was prepended to
330 <varname>ID_NET_LABEL_ONBOARD=
</varname>. This is not done anymore.
</para></listitem>
334 <para>Note that
<constant>latest
</constant> may be used to denote the latest scheme known (to this
335 particular version of systemd.
</para>
339 <title>Examples
</title>
342 <title>Using
<command>udevadm test-builtin
</command> to display device properties
</title>
344 <programlisting>$ udevadm test-builtin net_id /sys/class/net/enp0s31f6
346 Using default interface naming scheme 'v243'.
347 ID_NET_NAMING_SCHEME=v243
348 ID_NET_NAME_MAC=enx54ee75cb1dc0
349 ID_OUI_FROM_DATABASE=Wistron InfoComm(Kunshan)Co.,Ltd.
350 ID_NET_NAME_PATH=enp0s31f6
355 <title>PCI Ethernet card with firmware index
"1"</title>
357 <programlisting>ID_NET_NAME_ONBOARD=eno1
358 ID_NET_NAME_ONBOARD_LABEL=Ethernet Port
1
363 <title>PCI Ethernet card in hotplug slot with firmware index number
</title>
365 <programlisting># /sys/devices/pci0000:
00/
0000:
00:
1c
.3/
0000:
05:
00.0/net/ens1
366 ID_NET_NAME_MAC=enx000000000466
367 ID_NET_NAME_PATH=enp5s0
368 ID_NET_NAME_SLOT=ens1
</programlisting>
372 <title>PCI Ethernet multi-function card with
2 ports
</title>
374 <programlisting># /sys/devices/pci0000:
00/
0000:
00:
1c
.0/
0000:
02:
00.0/net/enp2s0f0
375 ID_NET_NAME_MAC=enx78e7d1ea46da
376 ID_NET_NAME_PATH=enp2s0f0
378 # /sys/devices/pci0000:
00/
0000:
00:
1c
.0/
0000:
02:
00.1/net/enp2s0f1
379 ID_NET_NAME_MAC=enx78e7d1ea46dc
380 ID_NET_NAME_PATH=enp2s0f1
</programlisting>
384 <title>PCI WLAN card
</title>
386 <programlisting># /sys/devices/pci0000:
00/
0000:
00:
1c
.1/
0000:
03:
00.0/net/wlp3s0
387 ID_NET_NAME_MAC=wlx0024d7e31130
388 ID_NET_NAME_PATH=wlp3s0
</programlisting>
392 <title>PCI IB host adapter with
2 ports
</title>
394 <programlisting># /sys/devices/pci0000:
00/
0000:
00:
03.0/
0000:
15:
00.0/net/ibp21s0f0
395 ID_NET_NAME_PATH=ibp21s0f0
397 # /sys/devices/pci0000:
00/
0000:
00:
03.0/
0000:
15:
00.1/net/ibp21s0f1
398 ID_NET_NAME_PATH=ibp21s0f1
</programlisting>
402 <title>USB built-in
3G modem
</title>
404 <programlisting># /sys/devices/pci0000:
00/
0000:
00:
1d
.0/usb2/
2-
1/
2-
1.4/
2-
1.4:
1.6/net/wwp0s29u1u4i6
405 ID_NET_NAME_MAC=wwx028037ec0200
406 ID_NET_NAME_PATH=wwp0s29u1u4i6
</programlisting>
410 <title>USB Android phone
</title>
412 <programlisting># /sys/devices/pci0000:
00/
0000:
00:
1d
.0/usb2/
2-
1/
2-
1.2/
2-
1.2:
1.0/net/enp0s29u1u2
413 ID_NET_NAME_MAC=enxd626b3450fb5
414 ID_NET_NAME_PATH=enp0s29u1u2
</programlisting>
418 <title>s390 grouped CCW interface
</title>
420 <programlisting># /sys/devices/css0/
0.0.0007/
0.0.f5f0/group_device/net/encf5f0
421 ID_NET_NAME_MAC=enx026d3c00000a
422 ID_NET_NAME_PATH=encf5f0
</programlisting>
427 <title>See Also
</title>
429 <citerefentry><refentrytitle>udev
</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
430 <citerefentry><refentrytitle>udevadm
</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
431 <ulink url=
"https://www.freedesktop.org/wiki/Software/systemd/PredictableNetworkInterfaceNames">the
432 original page describing stable interface names
</ulink>