systemd.net-naming-scheme(7) — systemd — Debian trixie — Debian Manpages

systemd.net-naming-scheme(7) — systemd — Debian trixie — Debian Manpages
MANPAGES
Skip Quicknav
Index
About Manpages
FAQ
Service Information
trixie
systemd
/ systemd.net-naming-scheme(7)
links
language-indep link
package tracker
raw man page
table of contents
NAME
DESCRIPTION
POLICIES
HISTORY
LIMITING THE USE OF SPECIFIC SYSFS ATTRIBUTES
EXAMPLES
SEE ALSO
NOTES
other versions
trixie
257.9-1~deb13u1
testing
260.1-1
unstable
260.1-1
other languages
Scroll to navigation
SYSTEMD.NET-NAMING-SCHEME(7)
systemd.net-naming-scheme
SYSTEMD.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(7)
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
systemd-udevd
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.
POLICIES
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(7)
net_id
builtin exports the following device
properties:
ID_NET_NAME_ONBOARD=
prefix
number
ID_NET_NAME_ONBOARD=
prefix
number
This name is set based on the numeric ordering
information given by the firmware for on-board devices. Different schemes are
used depending on the firmware type, as described in the table below.
Table 2. On-board naming schemes
Format
Description
prefix
number
PCI on-board index
prefix
number
DeviceTree alias index
Added in version 243.
ID_NET_LABEL_ONBOARD=
label
This property is set based on textual label given by the
firmware for on-board devices. This is only available for PCI devices.
Added in version 243.
ID_NET_NAME_MAC=
prefix
AABBCCDDEEFF
This name consists of the prefix, letter
, 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.
Added in version 243.
ID_NET_NAME_SLOT=
prefix
domain
slot
function
][
port_name
dev_port
],
ID_NET_NAME_SLOT=
prefix
slot
ID_NET_NAME_SLOT=
prefix
slot
ID_NET_NAME_SLOT=
prefix
domain
slot
function
][
port_name
dev_port
number
ID_NET_NAME_SLOT=
prefix
domain
slot
function
][
port_name
dev_port
port
...[
config
][
interface
],
ID_NET_NAME_SLOT=
prefix
domain
slot
function
][
port_name
dev_port
slot
ID_NET_NAME_SLOT=
prefix
domain
slot
function
][
port_name
dev_port
slot
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 3. Slot naming schemes
Format
Description
prefix
domain
slot
function
] [
port_name
dev_port
PCI slot number
prefix
slot
VIO slot number (IBM PowerVM)
prefix
number
VIF interface number (Xen)
...
number
Broadcom bus (BCMA) core number
...
port
... [
config
] [
interface
USB port number chain
...
slot
SR-VIO slot number
...
slot
SR-IOV slot number
The PCI domain is only prepended when it is not 0. All
multi-function PCI devices will carry the
function
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
dev_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
and the virtual device number, with any
leading zeros removed. The bus number is ignored.
SR-IOV virtual device representors are named based on the name of
the physical device interface, with a suffix of
and the number of
the virtual device that is linked to the particular representor, with any
leading zeros removed. The physical port name and the bus number are
ignored.
In some configurations a parent PCI bridge of a given network
controller may be associated with a slot. In such case we do not generate
this device property to avoid possible naming conflicts.
Added in version 243.
ID_NET_NAME_PATH=
prefix
bus_id
ID_NET_NAME_PATH=
prefix
vendor
model
instance
ID_NET_NAME_PATH=
prefix
address
port_name
ID_NET_NAME_PATH=
prefix
port
...,
ID_NET_NAME_PATH=
prefix
domain
bus
slot
function
][
phys_port_name
dev_port
],
ID_NET_NAME_PATH=
prefix
domain
bus
slot
function
][
phys_port_name
dev_port
number
ID_NET_NAME_PATH=
prefix
domain
bus
slot
function
][
phys_port_name
dev_port
port
...[
config
][
interface
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 4. Path naming schemes
Format
Description
prefix
bus_id
CCW or grouped CCW device identifier
prefix
vendor
model
instance
ACPI path names for ARM64 platform devices
prefix
address
port_name
Netdevsim (simulated networking device) device number and port name
prefix
domain
bus
slot
function
] [
phys_port_name
dev_port
PCI geographical location
...
number
Broadcom bus (BCMA) core number
...
port
... [
config
] [
interface
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.
Added in version 243.
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.
Added in version 243.
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 "v
port
", 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 ("eth
") 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.
Added in version 243.
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=
Added in version 243.
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.
Added in version 243.
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.
Added in version 243.
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).
Added in version 245.
v247
When a PCI slot is associated with a PCI bridge that has
multiple child network controllers, the same value of the
ID_NET_NAME_SLOT
property might be derived for those controllers. This
would cause a naming conflict if the property is selected as the device name.
Now, we detect this situation and do not produce the
ID_NET_NAME_SLOT
property.
Added in version 247.
v249
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 unreasonably
high numbers for the on-board index. To prevent the generation of bogus
on-board interface names, index numbers greater than 16381
(2¹⁴-1) were ignored. For s390 PCI devices index values up to
65535 (2¹⁶-1) are valid. To account for that, the limit was
increased to 65535.
The
udev(7)
rule
NAME=
replaces ":",
"/", and "%" with an underscore ("_"), and
refuses strings which contain only digits.
Added in version 249.
v250
Added naming scheme for Xen netfront "vif"
interfaces based on the guest side VIF number set from the Xen config (or the
interface index in AWS EC2).
Added in version 250.
v251
Since version
v247
we no longer set
ID_NET_NAME_SLOT
if we detect that a PCI device associated with a slot
is a PCI bridge as that would create naming conflict when there are more child
devices on that bridge. Now, this is relaxed and we will use slot information
to generate the name based on it but only if the PCI device has multiple
functions. This is safe because distinct function number is a part of the
device name for multifunction devices. Note, this is reverted in
v255
See below.
Added in version 251.
v252
Added naming scheme for platform devices with devicetree
aliases.
Added in version 252.
v253
Set
ID_NET_NAME_PATH
for usb devices not connected
via a PCI bus.
Added in version 253.
v254
Naming was changed for SR-IOV virtual device
representors, optionally settable at compilation time. The
"r
slot
" suffix was added to differentiate SR-IOV virtual
device representors attached to a single physical device interface. Because of
a mistake, this scheme was
not the default scheme for systemd version
254
Added in version 255.
v255
Naming was changed for SR-IOV virtual device representors
to enable the change introduced in
v254
by default.
If we detect that a PCI device associated with a slot is a PCI
bridge, we no longer set
ID_NET_NAME_SLOT
, reverting a change that
was introduced in
v251
Added in version 255.
v257
PCI slot number is now read from
firmware_node/sun
sysfs file.
The naming scheme based on devicetree aliases was extended to
support aliases for individual interfaces of controllers with multiple
ports.
Added in version 257.
Note that
latest
may be used to denote the latest scheme
known (to this particular version of systemd).
LIMITING THE USE OF SPECIFIC SYSFS ATTRIBUTES
When creating names for network cards, some naming schemes use
data from sysfs populated by the kernel. This means that although a specific
naming scheme in
udev(7)
is picked, the network card's name can still
change when a new kernel version adds a new sysfs attribute. For example, if
kernel starts setting the
phys_port_name
udev
will append the
phys_port_name
" suffix to the device name.
ID_NET_NAME_ALLOW=
BOOL
This udev property sets a fallback policy for reading a
sysfs attribute. If set to
udev will not read any sysfs attribute by
default, unless it is explicitly allowlisted, see below. If set to
udev can use any sysfs attribute unless it is explicitly forbidden. The
default value is
Added in version 256.
ID_NET_NAME_ALLOW_
sysfsattr
BOOL
This udev property explicitly states if udev shall use
the specified
sysfsattr
, when composing the device name.
Added in version 256.
With these options, users can set an allowlist or denylist for
sysfs attributes. To create an allowlist, the user needs to set
ID_NET_NAME_ALLOW=0
for the device and then list the allowed
attributes with the
ID_NET_NAME_ALLOW_
sysfsattr
=1
options. In case
of a denylist, the user needs to provide the list of denied attributes with
the
ID_NET_NAME_ALLOW_
sysfsattr
=0
options.
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 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
Example 10. Set an allowlist for reading sysfs
attributes for network card naming
/etc/udev/hwdb.d/50-net-naming-allowlist.hwdb
net:naming:drvirtio_net:*
ID_NET_NAME_ALLOW=0
ID_NET_NAME_ALLOW_ACPI_INDEX=1
ID_NET_NAME_ALLOW_ADDR_ASSIGN_TYPE=1
ID_NET_NAME_ALLOW_ADDRESS=1
ID_NET_NAME_ALLOW_ARI_ENABLED=1
ID_NET_NAME_ALLOW_DEV_PORT=1
ID_NET_NAME_ALLOW_FUNCTION_ID=1
ID_NET_NAME_ALLOW_IFLINK=1
ID_NET_NAME_ALLOW_INDEX=1
ID_NET_NAME_ALLOW_LABEL=1
ID_NET_NAME_ALLOW_PHYS_PORT_NAME=1
ID_NET_NAME_ALLOW_TYPE=1
Example 11. Set a denylist so that specified
sysfs attribute are ignored
/etc/udev/hwdb.d/50-net-naming-denylist.hwdb
net:naming:drvirtio_net:*
ID_NET_NAME_ALLOW=1
ID_NET_NAME_ALLOW_DEV_PORT=0
ID_NET_NAME_ALLOW_PHYS_PORT_NAME=0
SEE ALSO
udev(7)
udevadm(8)
systemd-udevd.service(8)
Predictable Network Interface
Names
[1],
systemd-nspawn(1)
NOTES
1.
Predictable Network Interface Names
systemd 257.9
Source file:
systemd.net-naming-scheme.7.en.gz (from
systemd 257.9-1~deb13u1
Source last updated:
2025-09-03T18:38:20Z
Converted to HTML:
2026-04-11T20:45:33Z
debiman HEAD, see
github.com/Debian/debiman
Found a problem? See the
FAQ