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.TH "NETWORKD\&.CONF" "5" "" "systemd 241" "networkd.conf"
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.SH "NAME"
networkd.conf, networkd.conf.d \- Global Network configuration files
.SH "SYNOPSIS"
.PP
/etc/systemd/networkd\&.conf
.PP
/etc/systemd/networkd\&.conf\&.d/*\&.conf
.PP
/lib/systemd/networkd\&.conf\&.d/*\&.conf
.SH "DESCRIPTION"
.PP
These configuration files control global network parameters\&. Currently the DHCP Unique Identifier (DUID)\&.
.SH "CONFIGURATION DIRECTORIES AND PRECEDENCE"
.PP
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\&.
.PP
When packages need to customize the configuration, they can install configuration snippets in
/usr/lib/systemd/*\&.conf\&.d/\&. Files in
/etc/
are reserved for the local administrator, who may use this logic to override the configuration files installed by vendor packages\&. 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 which of the subdirectories they reside in\&. 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 lexicographically\&. It is recommended to prefix all filenames in those subdirectories with a two\-digit number and a dash, to simplify the ordering of the files\&.
.PP
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 file\&.
.SH "[DHCP] SECTION OPTIONS"
.PP
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
\fBClientIdentifier=duid\fR\&. 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
\fBsystemd.network\fR(5)\&.
.PP
The following options are understood:
.PP
\fIDUIDType=\fR
.RS 4
Specifies how the DUID should be generated\&. See
\m[blue]\fBRFC 3315\fR\m[]\&\s-2\u[1]\d\s+2
for a description of all the options\&.
.sp
The following values are understood:
.PP
\fBvendor\fR
.RS 4
If
"DUIDType=vendor", then the DUID value will be generated using
"43793"
as the vendor identifier (systemd) and hashed contents of
\fBmachine-id\fR(5)\&. This is the default if
\fIDUIDType=\fR
is not specified\&.
.RE
.PP
\fBuuid\fR
.RS 4
If
"DUIDType=uuid", and
\fIDUIDRawData=\fR
is 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
\fBmachine-id\fR(5)
is used as a DUID value\&. About the application\-specific machine ID, see
\fBsd_id128_get_machine_app_specific\fR(3)\&.
.RE
.PP
\fBlink\-layer\-time[:\fR\fB\fITIME\fR\fR\fB]\fR, \fBlink\-layer\fR
.RS 4
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"\&.
.RE
.sp
In all cases,
\fIDUIDRawData=\fR
can be used to override the actual DUID value that is used\&.
.RE
.PP
\fIDUIDRawData=\fR
.RS 4
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
\fIDUIDType=\fR
and the value configured here\&.
.sp
The DUID value specified here overrides the DUID that
\fBsystemd-networkd.service\fR(8)
generates from the machine ID\&. To configure DUID per\-network, see
\fBsystemd.network\fR(5)\&. The configured DHCP DUID should conform to the specification in
\m[blue]\fBRFC 3315\fR\m[]\&\s-2\u[2]\d\s+2,
\m[blue]\fBRFC 6355\fR\m[]\&\s-2\u[3]\d\s+2\&. To configure IAID, see
\fBsystemd.network\fR(5)\&.
.PP
\fBExample\ \&1.\ \&A DUIDType=vendor with a custom value\fR
.sp
.if n \{\
.RS 4
.\}
.nf
DUIDType=vendor
DUIDRawData=00:00:ab:11:f9:2a:c2:77:29:f9:5c:00
.fi
.if n \{\
.RE
.\}
.sp
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"\&.
.RE
.SH "SEE ALSO"
.PP
\fBsystemd\fR(1),
\fBsystemd.network\fR(5),
\fBsystemd-networkd.service\fR(8),
\fBmachine-id\fR(5),
\fBsd_id128_get_machine_app_specific\fR(3)
.SH "NOTES"
.IP " 1." 4
RFC 3315
.RS 4
\%https://tools.ietf.org/html/rfc3315#section-9
.RE
.IP " 2." 4
RFC 3315
.RS 4
\%http://tools.ietf.org/html/rfc3315#section-9
.RE
.IP " 3." 4
RFC 6355
.RS 4
\%http://tools.ietf.org/html/rfc6355
.RE