networkd.conf, networkd.conf.d - Global Network configuration files
These configuration files control global network parameters. Currently the DHCP
Unique Identifier (DUID).
The default configuration is defined during compilation, so a configuration file
is only needed when it is necessary to deviate from those defaults. By
default, the configuration file in /etc/systemd/ contains commented out
entries showing the defaults as a guide to the administrator. This file can be
edited to create local overrides.
When packages need to customize the configuration, they can
install configuration snippets in /usr/lib/systemd/*.conf.d/ or
/usr/local/lib/systemd/*.conf.d/. The main configuration file is read before
any of the configuration directories, and has the lowest precedence; entries
in a file in any configuration directory override entries in the single
configuration file. Files in the *.conf.d/ configuration subdirectories are
sorted by their filename in lexicographic order, regardless of in which of
the subdirectories they reside. When multiple files specify the same option,
for options which accept just a single value, the entry in the file with the
lexicographically latest name takes precedence. For options which accept a
list of values, entries are collected as they occur in files sorted
Files in /etc/ are reserved for the local administrator, who may
use this logic to override the configuration files installed by vendor
packages. It is recommended to prefix all filenames in those subdirectories
with a two-digit number and a dash, to simplify the ordering of the
To disable a configuration file supplied by the vendor, the
recommended way is to place a symlink to /dev/null in the configuration
directory in /etc/, with the same filename as the vendor configuration
The following options are available in the [Network] section:
Takes a boolean. If set to yes, then
systemd-networkd measures the traffic of each interface, and
networkctl status INTERFACE shows the measured speed.
Defaults to no.
Specifies the time interval to calculate the traffic
speed of each interface. If SpeedMeter=no, the value is ignored.
Defaults to 10sec.
A boolean. When true, systemd-networkd will store
any routes configured by other tools in its memory. When false,
systemd-networkd will not manage the foreign routes, thus they are kept
even if KeepConfiguration= is false. Defaults to yes.
This section configures the DHCP Unique Identifier (DUID) value used by DHCP
protocol. DHCPv6 client protocol sends the DHCP Unique Identifier and the
interface Identity Association Identifier (IAID) to a DHCP server when
acquiring a dynamic IPv6 address. DHCPv4 client protocol sends IAID and DUID
to the DHCP server when acquiring a dynamic IPv4 address if
ClientIdentifier=duid. IAID and DUID allows a DHCP server to uniquely
identify the machine and the interface requesting a DHCP IP. To configure IAID
and ClientIdentifier, see systemd.network(5).
The following options are understood:
Specifies how the DUID should be generated. See RFC
 for a description of all the options.
The following values are understood:
If "DUIDType=vendor", then the DUID value will
be generated using "43793" as the vendor identifier (systemd) and
hashed contents of machine-id(5)
. This is the default if
is not specified.
If "DUIDType=uuid", and DUIDRawData=
not set, then the product UUID is used as a DUID value. If a system does not
have valid product UUID, then an application-specific machine-id(5)
used as a DUID value. About the application-specific machine ID, see
If "link-layer-time" or "link-layer"
is specified, then the MAC address of the interface is used as a DUID value.
The value "link-layer-time" can take additional time value after a
colon, e.g. "link-layer-time:2018-01-23 12:34:56 UTC". The default
time value is "2000-01-01 00:00:00 UTC".
In all cases, DUIDRawData= can be used to override the
actual DUID value that is used.
Specifies the DHCP DUID value as a single
newline-terminated, hexadecimal string, with each byte separated by
":". The DUID that is sent is composed of the DUID type specified by
and the value configured here.
The DUID value specified here overrides the DUID that
systemd-networkd.service(8) generates from the machine ID. To
configure DUID per-network, see systemd.network(5). The configured
DHCP DUID should conform to the specification in RFC 3315, RFC
6355. To configure IAID, see systemd.network(5).
Example 1. A DUIDType=vendor with a custom
This specifies a 14 byte DUID, with the type DUID-EN
("00:02"), enterprise number 43793 ("00:00:ab:11"), and
identifier value "f9:2a:c2:77:29:f9:5c:00".
- RFC 3315
- RFC 3315
- RFC 6355