NETWORKD.CONF(5)                networkd.conf               NETWORKD.CONF(5)

NAME         top

       networkd.conf, networkd.conf.d - Global Network configuration files

SYNOPSIS         top




DESCRIPTION         top

       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

       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. If multiple files specify the same
       option, the entry in the file with the lexicographically latest name
       takes precedence. 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.

       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.


       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

       The following options are understood:

           Specifies how the DUID should be generated. See RFC 3315[1] 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 DUIDType=
               is not specified.

           link-layer-time, link-layer, uuid
               Those values are parsed and can be used to set the DUID type
               field, but DUID contents must be provided using DUIDRawData=.

           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 DUIDType=
           and the value configured here.

           The DUID value specified here overrides the DUID that
           systemd-networkd generates using the machine-id from the
           /etc/machine-id file. To configure DUID per-network, see
  The configured DHCP DUID should conform to
           the specification in RFC 3315[2], RFC 6355[3]. To configure IAID,

           Example 1. A DUIDType=vendor with a custom value


           This specifies a 14 byte DUID, with the type DUID-EN ("00:02"),
           enterprise number 43793 ("00:00:ab:11"), and identifier value

SEE ALSO         top

       systemd(1),, machine-id(1)

NOTES         top

        1. RFC 3315

        2. RFC 3315

        3. RFC 6355

COLOPHON         top

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systemd 234                                                 NETWORKD.CONF(5)

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