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
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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, ID_NET_NAME_SLOT=prefixxslot,
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 │prefix Xnumber │ VIF interface number (Xen) │
104 ├────────────────────────────────────────────────────────────┼────────────────────────────┤
105 │... bnumber │ Broadcom bus (BCMA) core │
106 │ │ number │
107 ├────────────────────────────────────────────────────────────┼────────────────────────────┤
108 │... uport... [cconfig] [iinterface] │ USB port number chain │
109 ├────────────────────────────────────────────────────────────┼────────────────────────────┤
110 │... vslot │ SR-VIO slot number │
111 └────────────────────────────────────────────────────────────┴────────────────────────────┘
112 The PCI domain is only prepended when it is not 0. All
113 multi-function PCI devices will carry the ffunction number in the
114 device name, including the function 0 device. For
115 non-multi-function devices, the number is suppressed if 0. The port
116 name port_name is used, or the port number ddev_port if the name is
117 not known.
118 For BCMA devices, the core number is suppressed when 0.
120 For USB devices the full chain of port numbers of hubs is composed.
122 If the name gets longer than the maximum number of 15 characters,
123 the name is not exported. The usual USB configuration number 1 and
124 interface number 0 values are suppressed.
125 SR-IOV virtual devices are named based on the name of the parent
127 interface, with a suffix of v and the virtual device number, with
128 any leading zeros removed. The bus number is ignored.
129 In some configurations a parent PCI bridge of a given network
131 controller may be associated with a slot. In such case we don't
132 generate this device property to avoid possible naming conflicts.
133 ID_NET_NAME_PATH=prefixcbus_id,
135 ID_NET_NAME_PATH=prefixavendormodeliinstance,
136 ID_NET_NAME_PATH=prefixiaddressnport_name,
137 ID_NET_NAME_PATH=prefix[Pdomain]pbussslot[ffunction][nphys_port_name|ddev_port],
138 ID_NET_NAME_PATH=prefix[Pdomain]pbussslot[ffunction][nphys_port_name|ddev_port]bnumber,
139 ID_NET_NAME_PATH=prefix[Pdomain]pbussslot[ffunction][nphys_port_name|ddev_port]uport...[cconfig][iinterface]
140 This property describes the device installation location. Different
141 schemes are used depending on the bus type, as described in the
142 table below. For BCMA and USB devices, PCI path information must
143 known, and the full name consists of the prefix, PCI slot
144 identifier, and USB or BCMA location. The first two parts are
145 denoted as "..." in the table below.
146 Table 3. Path naming schemes
148 ┌──────────────────────────────────────────────────────────────────────┬───────────────────────────┐
149 │Format │ Description │
150 ├──────────────────────────────────────────────────────────────────────┼───────────────────────────┤
151 │prefix cbus_id │ CCW or grouped CCW device │
152 │ │ identifier │
153 ├──────────────────────────────────────────────────────────────────────┼───────────────────────────┤
154 │prefix avendor model iinstance │ ACPI path names for ARM64 │
155 │ │ platform devices │
156 ├──────────────────────────────────────────────────────────────────────┼───────────────────────────┤
157 │prefix iaddress nport_name │ Netdevsim (simulated │
158 │ │ networking device) device │
159 │ │ number and port name │
160 ├──────────────────────────────────────────────────────────────────────┼───────────────────────────┤
161 │prefix [Pdomain] pbus sslot [ffunction] [nphys_port_name | ddev_port] │ PCI geographical location │
162 ├──────────────────────────────────────────────────────────────────────┼───────────────────────────┤
163 │... bnumber │ Broadcom bus (BCMA) core │
164 │ │ number │
165 ├──────────────────────────────────────────────────────────────────────┼───────────────────────────┤
166 │... uport... [cconfig] [iinterface] │ USB port number chain │
167 └──────────────────────────────────────────────────────────────────────┴───────────────────────────┘
168 CCW and grouped CCW devices are found in IBM System Z mainframes.
169 Any leading zeros and dots are suppressed.
170 For PCI, BCMA, and USB devices, the same rules as described above
172 for slot naming are used.
173
175 The following "naming schemes" have been defined (which may be chosen
176 at system boot-up time via the net.naming-scheme= kernel command line
177 switch, see above):
178 v238
180 This is the naming scheme that was implemented in systemd 238.
181 v239
183 Naming was changed for virtual network interfaces created with
184 SR-IOV and NPAR and for devices where the PCI network controller
185 device does not have a slot number associated.
186 SR-IOV virtual devices are named based on the name of the parent
188 interface, with a suffix of "vport", where port is the virtual
189 device number. Previously those virtual devices were named as if
190 completely independent.
191 The ninth and later NPAR virtual devices are named following the
193 scheme used for the first eight NPAR partitions. Previously those
194 devices were not renamed and the kernel default ("ethN") was used.
195 Names are also generated for PCI devices where the PCI network
197 controller device does not have an associated slot number itself,
198 but one of its parents does. Previously those devices were not
199 renamed and the kernel default was used.
200 v240
202 The "ib" prefix and stable names for infiniband devices are
203 introduced. Previously those devices were not renamed.
204 The ACPI index field (used in ID_NET_NAME_ONBOARD=) is now also
206 used when 0.
207 A new naming policy NamePolicy=keep was introduced. With this
209 policy, if the network device name was already set by userspace,
210 the device will not be renamed again. Previously, this naming
211 policy applied implicitly, and now it must be explicitly requested.
212 Effectively, this means that network devices will be renamed
213 according to the configuration, even if they have been renamed
214 already, if keep is not specified as the naming policy in the .link
215 file. See systemd.link(5) for a description of NamePolicy=.
216 v241
218 MACAddressPolicy=persistent was extended to set MAC addresses based
219 on the device name. Previously addresses were only based on the
220 ID_NET_NAME_* attributes, which meant that interface names would
221 never be generated for virtual devices. Now a persistent address
222 will be generated for most devices, including in particular
223 bridges.
224 Note: when userspace does not set a MAC address for a bridge
226 device, the kernel will initially assign a random address, and then
227 change it when the first device is enslaved to the bridge. With
228 this naming policy change, bridges get a persistent MAC address
229 based on the bridge name instead of the first enslaved device.
230 v243
232 Support for renaming netdevsim (simulated networking) devices was
233 added. Previously those devices were not renamed.
234 Previously two-letter interface type prefix was prepended to
236 ID_NET_LABEL_ONBOARD=. This is not done anymore.
237 v245
239 When systemd-nspawn(1) derives the name for the host side of the
240 network interface created with --network-veth from the container
241 name it previously simply truncated the result at 15 characters if
242 longer (since that's the maximum length for network interface
243 names). From now on, for any interface name that would be longer
244 than 15 characters the last 4 characters are set to a 24bit hash
245 value of the full interface name. This way network interface name
246 collisions between multiple similarly named containers (who only
247 differ in container name suffix) should be less likely (but still
248 possible, since the 24bit hash value is very small).
249 v247
251 When a PCI slot is associated with a PCI bridge that has multiple
252 child network controllers, the same value of the ID_NET_NAME_SLOT
253 property might be derived for those controllers. This would cause a
254 naming conflict if the property is selected as the device name.
255 Now, we detect this situation and don't produce the
256 ID_NET_NAME_SLOT property.
257 v249
259 PCI hotplug slot names for the s390 PCI driver are a hexadecimal
260 representation of the function_id device attribute. This attribute
261 is now used to build the ID_NET_NAME_SLOT. Before that, all slot
262 names were parsed as decimal numbers, which could either result in
263 an incorrect value of the ID_NET_NAME_SLOT property or none at all.
264 Some firmware and hypervisor implementations report unreasonably
266 high numbers for the onboard index. To prevent the generation of
267 bogus onbard interface names, index numbers greater than 16381
268 (2¹⁴-1) were ignored. For s390 PCI devices index values up to 65535
269 (2¹⁶-1) are valid. To account for that, the limit was increased to
270 65535.
271 The udev rule NAME= replaces ":", "/", and "%" with an underscore
273 ("_"), and refuses strings which contain only numerics.
274 v250
276 Added naming scheme for Xen netfront "vif" interfaces based on the
277 guest side VIF number set from the Xen config (or the interface
278 index in AWS EC2).
279 v251
281 Since version v247 we no longer set ID_NET_NAME_SLOT if we detect
282 that a PCI device associated with a slot is a PCI bridge as that
283 would create naming conflict when there are more child devices on
284 that bridge. Now, this is relaxed and we will use slot information
285 to generate the name based on it but only if the PCI device has
286 multiple functions. This is safe because distinct function number
287 is a part of the device name for multifunction devices.
288 Note that latest may be used to denote the latest scheme known (to this
290 particular version of systemd).
291
293 Example 1. Using udevadm test-builtin to display device properties
294 $ udevadm test-builtin net_id /sys/class/net/enp0s31f6
296 ...
297 Using default interface naming scheme 'v243'.
298 ID_NET_NAMING_SCHEME=v243
299 ID_NET_NAME_MAC=enx54ee75cb1dc0
300 ID_OUI_FROM_DATABASE=Wistron InfoComm(Kunshan)Co.,Ltd.
301 ID_NET_NAME_PATH=enp0s31f6
302 ...
303 Example 2. PCI Ethernet card with firmware index "1"
305 ID_NET_NAME_ONBOARD=eno1
307 ID_NET_NAME_ONBOARD_LABEL=Ethernet Port 1
308 Example 3. PCI Ethernet card in hotplug slot with firmware index number
311 # /sys/devices/pci0000:00/0000:00:1c.3/0000:05:00.0/net/ens1
313 ID_NET_NAME_MAC=enx000000000466
314 ID_NET_NAME_PATH=enp5s0
315 ID_NET_NAME_SLOT=ens1
316 Example 4. PCI Ethernet multi-function card with 2 ports
318 # /sys/devices/pci0000:00/0000:00:1c.0/0000:02:00.0/net/enp2s0f0
320 ID_NET_NAME_MAC=enx78e7d1ea46da
321 ID_NET_NAME_PATH=enp2s0f0
322 # /sys/devices/pci0000:00/0000:00:1c.0/0000:02:00.1/net/enp2s0f1
324 ID_NET_NAME_MAC=enx78e7d1ea46dc
325 ID_NET_NAME_PATH=enp2s0f1
326 Example 5. PCI WLAN card
328 # /sys/devices/pci0000:00/0000:00:1c.1/0000:03:00.0/net/wlp3s0
330 ID_NET_NAME_MAC=wlx0024d7e31130
331 ID_NET_NAME_PATH=wlp3s0
332 Example 6. PCI IB host adapter with 2 ports
334 # /sys/devices/pci0000:00/0000:00:03.0/0000:15:00.0/net/ibp21s0f0
336 ID_NET_NAME_PATH=ibp21s0f0
337 # /sys/devices/pci0000:00/0000:00:03.0/0000:15:00.1/net/ibp21s0f1
339 ID_NET_NAME_PATH=ibp21s0f1
340 Example 7. USB built-in 3G modem
342 # /sys/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.4/2-1.4:1.6/net/wwp0s29u1u4i6
344 ID_NET_NAME_MAC=wwx028037ec0200
345 ID_NET_NAME_PATH=wwp0s29u1u4i6
346 Example 8. USB Android phone
348 # /sys/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.2/2-1.2:1.0/net/enp0s29u1u2
350 ID_NET_NAME_MAC=enxd626b3450fb5
351 ID_NET_NAME_PATH=enp0s29u1u2
352 Example 9. s390 grouped CCW interface
354 # /sys/devices/css0/0.0.0007/0.0.f5f0/group_device/net/encf5f0
356 ID_NET_NAME_MAC=enx026d3c00000a
357 ID_NET_NAME_PATH=encf5f0
358
360 udev(7), udevadm(8), Predictable Network Interface Names[1], systemd-
361 nspawn(1)
362
364 1. Predictable Network Interface Names
365 https://systemd.io/PREDICTABLE_INTERFACE_NAMES
366systemd 251 SYSTEMD.NET-NAMING-SCHEME(7)