1SYSTEMD.NET-NAMING-SCHEME(7)systemd.net-naming-schemSeYSTEMD.NET-NAMING-SCHEME(7)
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6 systemd.net-naming-scheme - Network device naming schemes
7
9 Network interfaces names and MAC addresses may be generated based on
10 certain stable interface attributes. This is possible when there is
11 enough information about the device to generate those attributes and
12 the use of this information is configured. This page describes
13 interface naming, i.e. what possible names may be generated. Those
14 names are generated by the systemd-udevd.service(8) builtin net_id and
15 exported as udev properties (ID_NET_NAME_ONBOARD=,
16 ID_NET_LABEL_ONBOARD=, ID_NET_NAME_PATH=, ID_NET_NAME_SLOT=).
17 Names and MAC addresses are derived from various stable device metadata
19 attributes. Newer versions of udev take more of these attributes into
20 account, improving (and thus possibly changing) the names and addresses
21 used for the same devices. Different versions of those generation rules
22 are called "naming schemes". The default naming scheme is chosen at
23 compilation time. Usually this will be the latest implemented version,
24 but it is also possible to set one of the older versions to preserve
25 compatibility. This may be useful for example for distributions, which
26 may introduce new versions of systemd in stable releases without
27 changing the naming scheme. The naming scheme may also be overridden
28 using the net.naming-scheme= kernel command line switch, see systemd-
29 udevd.service(8). Available naming schemes are described below.
30 After the udev properties have been generated, appropriate udev rules
32 may be used to actually rename devices based on those properties. See
33 the description of NamePolicy= and MACAddressPolicy= in
34 systemd.link(5).
35 Note that while the concept of network interface naming schemes is
37 primarily relevant in the context of systemd-udevd.service, the
38 systemd-nspawn(1) container manager also takes it into account when
39 naming network interfaces, see below.
40
42 All names start with a two-character prefix that signifies the
43 interface type.
44 Table 1. Two character prefixes based on the type of interface
46 ┌───────┬────────────────────────────┐
47 │Prefix │ Description │
48 ├───────┼────────────────────────────┤
49 │en │ Ethernet │
50 ├───────┼────────────────────────────┤
51 │ib │ InfiniBand │
52 ├───────┼────────────────────────────┤
53 │sl │ Serial line IP (slip) │
54 ├───────┼────────────────────────────┤
55 │wl │ Wireless local area │
56 │ │ network (WLAN) │
57 ├───────┼────────────────────────────┤
58 │ww │ Wireless wide area network │
59 │ │ (WWAN) │
60 └───────┴────────────────────────────┘
61 The udev net_id builtin exports the following udev device properties:
63 ID_NET_NAME_ONBOARD=prefixonumber
65 This name is set based on the numeric ordering information given by
66 the firmware for on-board devices. The name consists of the prefix,
67 letter o, and a number specified by the firmware. This is only
68 available for PCI devices.
69 ID_NET_LABEL_ONBOARD=prefix label
71 This property is set based on textual label given by the firmware
72 for on-board devices. The name consists of the prefix concatenated
73 with the label. This is only available for PCI devices.
74 ID_NET_NAME_MAC=prefixxAABBCCDDEEFF
76 This name consists of the prefix, letter x, and 12 hexadecimal
77 digits of the MAC address. It is available if the device has a
78 fixed MAC address. Because this name is based on an attribute of
79 the card itself, it remains "stable" when the device is moved (even
80 between machines), but will change when the hardware is replaced.
81 ID_NET_NAME_SLOT=prefix[Pdomain]sslot[ffunction][nport_name|ddev_port],
83 ID_NET_NAME_SLOT=prefixvslot,
84 ID_NET_NAME_SLOT=prefix[Pdomain]sslot[ffunction][nport_name|ddev_port]bnumber,
85 ID_NET_NAME_SLOT=prefix[Pdomain]sslot[ffunction][nport_name|ddev_port]uport...[cconfig][iinterface],
86 ID_NET_NAME_SLOT=prefix[Pdomain]sslot[ffunction][nport_name|ddev_port]vslot
87 This property describes the slot position. Different schemes are
88 used depending on the bus type, as described in the table below. In
89 case of USB, BCMA, and SR-VIO devices, the full name consists of
90 the prefix, PCI slot identifier, and USB or BCMA or SR-VIO slot
91 identifier. The first two parts are denoted as "..." in the table
92 below.
93 Table 2. Slot naming schemes
95 ┌────────────────────────────────────────────────────────────┬──────────────────────────┐
96 │Format │ Description │
97 ├────────────────────────────────────────────────────────────┼──────────────────────────┤
98 │prefix [Pdomain] sslot [ffunction] [nport_name | ddev_port] │ PCI slot number │
99 ├────────────────────────────────────────────────────────────┼──────────────────────────┤
100 │prefix vslot │ VIO slot number (IBM │
101 │ │ PowerVM) │
102 ├────────────────────────────────────────────────────────────┼──────────────────────────┤
103 │... bnumber │ Broadcom bus (BCMA) core │
104 │ │ number │
105 ├────────────────────────────────────────────────────────────┼──────────────────────────┤
106 │... uport... [cconfig] [iinterface] │ USB port number chain │
107 ├────────────────────────────────────────────────────────────┼──────────────────────────┤
108 │... vslot │ SR-VIO slot number │
109 └────────────────────────────────────────────────────────────┴──────────────────────────┘
110 The PCI domain is only prepended when it is not 0. All
111 multi-function PCI devices will carry the ffunction number in the
112 device name, including the function 0 device. For
113 non-multi-function devices, the number is suppressed if 0. The port
114 name port_name is used, or the port number ddev_port if the name is
115 not known.
116 For BCMA devices, the core number is suppressed when 0.
118 For USB devices the full chain of port numbers of hubs is composed.
120 If the name gets longer than the maximum number of 15 characters,
121 the name is not exported. The usual USB configuration number 1 and
122 interface number 0 values are suppressed.
123 SR-IOV virtual devices are named based on the name of the parent
125 interface, with a suffix of v and the virtual device number, with
126 any leading zeros removed. The bus number is ignored.
127 In some configurations a parent PCI bridge of a given network
129 controller may be associated with a slot. In such case we don't
130 generate this device property to avoid possible naming conflicts.
131 ID_NET_NAME_PATH=prefixcbus_id,
133 ID_NET_NAME_PATH=prefixavendormodeliinstance,
134 ID_NET_NAME_PATH=prefixiaddressnport_name,
135 ID_NET_NAME_PATH=prefix[Pdomain]pbussslot[ffunction][nphys_port_name|ddev_port],
136 ID_NET_NAME_PATH=prefix[Pdomain]pbussslot[ffunction][nphys_port_name|ddev_port]bnumber,
137 ID_NET_NAME_PATH=prefix[Pdomain]pbussslot[ffunction][nphys_port_name|ddev_port]uport...[cconfig][iinterface]
138 This property describes the device installation location. Different
139 schemes are used depending on the bus type, as described in the
140 table below. For BCMA and USB devices, PCI path information must
141 known, and the full name consists of the prefix, PCI slot
142 identifier, and USB or BCMA location. The first two parts are
143 denoted as "..." in the table below.
144 Table 3. Path naming schemes
146 ┌──────────────────────────────────────────────────────────────────────┬───────────────────────────┐
147 │Format │ Description │
148 ├──────────────────────────────────────────────────────────────────────┼───────────────────────────┤
149 │prefix cbus_id │ CCW or grouped CCW device │
150 │ │ identifier │
151 ├──────────────────────────────────────────────────────────────────────┼───────────────────────────┤
152 │prefix avendor model iinstance │ ACPI path names for ARM64 │
153 │ │ platform devices │
154 ├──────────────────────────────────────────────────────────────────────┼───────────────────────────┤
155 │prefix iaddress nport_name │ Netdevsim (simulated │
156 │ │ networking device) device │
157 │ │ number and port name │
158 ├──────────────────────────────────────────────────────────────────────┼───────────────────────────┤
159 │prefix [Pdomain] pbus sslot [ffunction] [nphys_port_name | ddev_port] │ PCI geographical location │
160 ├──────────────────────────────────────────────────────────────────────┼───────────────────────────┤
161 │... bnumber │ Broadcom bus (BCMA) core │
162 │ │ number │
163 ├──────────────────────────────────────────────────────────────────────┼───────────────────────────┤
164 │... uport... [cconfig] [iinterface] │ USB port number chain │
165 └──────────────────────────────────────────────────────────────────────┴───────────────────────────┘
166 CCW and grouped CCW devices are found in IBM System Z mainframes.
167 Any leading zeros and dots are suppressed.
168 For PCI, BCMA, and USB devices, the same rules as described above
170 for slot naming are used.
171
173 The following "naming schemes" have been defined (which may be chosen
174 at system boot-up time via the net.naming-scheme= kernel command line
175 switch, see above):
176 v238
178 This is the naming scheme that was implemented in systemd 238.
179 v239
181 Naming was changed for virtual network interfaces created with
182 SR-IOV and NPAR and for devices where the PCI network controller
183 device does not have a slot number associated.
184 SR-IOV virtual devices are named based on the name of the parent
186 interface, with a suffix of "vport", where port is the virtual
187 device number. Previously those virtual devices were named as if
188 completely independent.
189 The ninth and later NPAR virtual devices are named following the
191 scheme used for the first eight NPAR partitions. Previously those
192 devices were not renamed and the kernel default ("ethN") was used.
193 Names are also generated for PCI devices where the PCI network
195 controller device does not have an associated slot number itself,
196 but one of its parents does. Previously those devices were not
197 renamed and the kernel default was used.
198 v240
200 The "ib" prefix and stable names for infiniband devices are
201 introduced. Previously those devices were not renamed.
202 The ACPI index field (used in ID_NET_NAME_ONBOARD=) is now also
204 used when 0.
205 A new naming policy NamePolicy=keep was introduced. With this
207 policy, if the network device name was already set by userspace,
208 the device will not be renamed again. Previously, this naming
209 policy applied implicitly, and now it must be explicitly requested.
210 Effectively, this means that network devices will be renamed
211 according to the configuration, even if they have been renamed
212 already, if keep is not specified as the naming policy in the .link
213 file. See systemd.link(5) for a description of NamePolicy=.
214 v241
216 MACAddressPolicy=persistent was extended to set MAC addresses based
217 on the device name. Previously addresses were only based on the
218 ID_NET_NAME_* attributes, which meant that interface names would
219 never be generated for virtual devices. Now a persistent address
220 will be generated for most devices, including in particular
221 bridges.
222 Note: when userspace does not set a MAC address for a bridge
224 device, the kernel will initially assign a random address, and then
225 change it when the first device is enslaved to the bridge. With
226 this naming policy change, bridges get a persistent MAC address
227 based on the bridge name instead of the first enslaved device.
228 v243
230 Support for renaming netdevsim (simulated networking) devices was
231 added. Previously those devices were not renamed.
232 Previously two-letter interface type prefix was prepended to
234 ID_NET_LABEL_ONBOARD=. This is not done anymore.
235 v245
237 When systemd-nspawn(1) derives the name for the host side of the
238 network interface created with --network-veth from the container
239 name it previously simply truncated the result at 15 characters if
240 longer (since that's the maximum length for network interface
241 names). From now on, for any interface name that would be longer
242 than 15 characters the last 4 characters are set to a 24bit hash
243 value of the full interface name. This way network interface name
244 collisions between multiple similarly named containers (who only
245 differ in container name suffix) should be less likely (but still
246 possible, since the 24bit hash value is very small).
247 v247
249 When a PCI slot is associated with a PCI bridge that has multiple
250 child network controllers, the same value of the ID_NET_NAME_SLOT
251 property might be derived for those controllers. This would cause a
252 naming conflict if the property is selected as the device name.
253 Now, we detect this situation and don't produce the
254 ID_NET_NAME_SLOT property.
255 v249
257 PCI hotplug slot names for the s390 PCI driver are a hexadecimal
258 representation of the function_id device attribute. This attribute
259 is now used to build the ID_NET_NAME_SLOT. Before that, all slot
260 names were parsed as decimal numbers, which could either result in
261 an incorrect value of the ID_NET_NAME_SLOT property or none at all.
262 Some firmware and hypervisor implementations report unreasonable
264 high numbers for the onboard index. To prevent the generation of
265 bogus onbard interface names, index numbers greater than 16381
266 (2^14-1) were ignored. For s390 PCI devices index values up to
267 65535 (2^16-1) are valid. To account for that, the limit is
268 increased to now 65535.
269 The udev rule NAME= replaces ":", "/", and "%" with an underscore
271 ("_"), and refuses strings which contain only numerics.
272 Note that latest may be used to denote the latest scheme known (to this
274 particular version of systemd).
275
277 Example 1. Using udevadm test-builtin to display device properties
278 $ udevadm test-builtin net_id /sys/class/net/enp0s31f6
280 ...
281 Using default interface naming scheme 'v243'.
282 ID_NET_NAMING_SCHEME=v243
283 ID_NET_NAME_MAC=enx54ee75cb1dc0
284 ID_OUI_FROM_DATABASE=Wistron InfoComm(Kunshan)Co.,Ltd.
285 ID_NET_NAME_PATH=enp0s31f6
286 ...
287 Example 2. PCI Ethernet card with firmware index "1"
289 ID_NET_NAME_ONBOARD=eno1
291 ID_NET_NAME_ONBOARD_LABEL=Ethernet Port 1
292 Example 3. PCI Ethernet card in hotplug slot with firmware index number
295 # /sys/devices/pci0000:00/0000:00:1c.3/0000:05:00.0/net/ens1
297 ID_NET_NAME_MAC=enx000000000466
298 ID_NET_NAME_PATH=enp5s0
299 ID_NET_NAME_SLOT=ens1
300 Example 4. PCI Ethernet multi-function card with 2 ports
302 # /sys/devices/pci0000:00/0000:00:1c.0/0000:02:00.0/net/enp2s0f0
304 ID_NET_NAME_MAC=enx78e7d1ea46da
305 ID_NET_NAME_PATH=enp2s0f0
306 # /sys/devices/pci0000:00/0000:00:1c.0/0000:02:00.1/net/enp2s0f1
308 ID_NET_NAME_MAC=enx78e7d1ea46dc
309 ID_NET_NAME_PATH=enp2s0f1
310 Example 5. PCI WLAN card
312 # /sys/devices/pci0000:00/0000:00:1c.1/0000:03:00.0/net/wlp3s0
314 ID_NET_NAME_MAC=wlx0024d7e31130
315 ID_NET_NAME_PATH=wlp3s0
316 Example 6. PCI IB host adapter with 2 ports
318 # /sys/devices/pci0000:00/0000:00:03.0/0000:15:00.0/net/ibp21s0f0
320 ID_NET_NAME_PATH=ibp21s0f0
321 # /sys/devices/pci0000:00/0000:00:03.0/0000:15:00.1/net/ibp21s0f1
323 ID_NET_NAME_PATH=ibp21s0f1
324 Example 7. USB built-in 3G modem
326 # /sys/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.4/2-1.4:1.6/net/wwp0s29u1u4i6
328 ID_NET_NAME_MAC=wwx028037ec0200
329 ID_NET_NAME_PATH=wwp0s29u1u4i6
330 Example 8. USB Android phone
332 # /sys/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.2/2-1.2:1.0/net/enp0s29u1u2
334 ID_NET_NAME_MAC=enxd626b3450fb5
335 ID_NET_NAME_PATH=enp0s29u1u2
336 Example 9. s390 grouped CCW interface
338 # /sys/devices/css0/0.0.0007/0.0.f5f0/group_device/net/encf5f0
340 ID_NET_NAME_MAC=enx026d3c00000a
341 ID_NET_NAME_PATH=encf5f0
342
344 udev(7), udevadm(8), Predictable Network Interface Names[1], systemd-
345 nspawn(1)
346
348 1. Predictable Network Interface Names
349 https://systemd.io/PREDICTABLE_INTERFACE_NAMES
350systemd 249 SYSTEMD.NET-NAMING-SCHEME(7)