systemd networkd.conf 5 networkd.conf networkd.conf.d Global Network configuration files /etc/systemd/networkd.conf /etc/systemd/networkd.conf.d/*.conf /usr/lib/systemd/networkd.conf.d/*.conf These configuration files control global network parameters. Currently the DHCP Unique Identifier (DUID). 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.network5. The following options are understood: DUIDType= Specifies how the DUID should be generated. See RFC 3315 for a description of all the options. The following values are understood: vendor If DUIDType=vendor, then the DUID value will be generated using 43793 as the vendor identifier (systemd) and hashed contents of machine-id5. 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. DUIDRawData= 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 systemd.network5. The configured DHCP DUID should conform to the specification in RFC 3315, RFC 6355. To configure IAID, see systemd.network5 . DUIDType=vendor DUIDRawData=00:00:ab:11:f9:2a:c2:77:29:f9:5c:00 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. systemd1, systemd.network5, machine-id1