NETWORKD.CONF(5)

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

SYNOPSIS

    /etc/systemd/networkd.conf
    /run/systemd/networkd.conf
    /usr/local/lib/systemd/networkd.conf
    /usr/lib/systemd/networkd.conf
    /etc/systemd/networkd.conf.d/*.conf
    /run/systemd/networkd.conf.d/*.conf
    /usr/local/lib/systemd/networkd.conf.d/*.conf
    /usr/lib/systemd/networkd.conf.d/*.conf

DESCRIPTION

These configuration files control global network parameters.

CONFIGURATION DIRECTORIES AND PRECEDENCE

The default configuration is set during compilation, so configuration is only needed when it is necessary to deviate from those defaults. The main configuration file is loaded from one of the listed directories in order of priority, only the first file found is used: /etc/systemd/, /run/systemd/, /usr/local/lib/systemd/ [1], /usr/lib/systemd/. The vendor version of the file contains commented out entries showing the defaults as a guide to the administrator. Local overrides can also be created by creating drop-ins, as described below. The main configuration file can also be edited for this purpose (or a copy in /etc/ if it is shipped under /usr/), however using drop-ins for local configuration is recommended over modifications to the main configuration file.

In addition to the main configuration file, drop-in configuration snippets are read from /usr/lib/systemd/*.conf.d/, /usr/local/lib/systemd/*.conf.d/, and /etc/systemd/*.conf.d/. Those drop-ins have higher precedence and override the main 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 sorted last takes precedence, and for options which accept a list of values, entries are collected as they occur in the sorted files.

When packages need to customize the configuration, they can install drop-ins under /usr/. Files in /etc/ are reserved for the local administrator, who may use this logic to override the configuration files installed by vendor packages. Drop-ins have to be used to override package drop-ins, since the main configuration file has lower precedence. It is recommended to prefix all filenames in those subdirectories with a two-digit number and a dash, to simplify the ordering. This also defines a concept of drop-in priorities to allow OS vendors to ship drop-ins within a specific range lower than the range used by users. This should lower the risk of package drop-ins overriding accidentally drop-ins defined by users. It is recommended to use the range 10-40 for drop-ins in /usr/ and the range 60-90 for drop-ins in /etc/ and /run/, to make sure that local and transient drop-ins take priority over drop-ins shipped by the OS vendor.

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.

[NETWORK] SECTION OPTIONS

The following options are available in the [Network] section:

SpeedMeter=
    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.

    Added in version 244.

SpeedMeterIntervalSec=
    Specifies the time interval to calculate the traffic speed of each interface. If SpeedMeter=no, the value is ignored. Defaults to 10sec.

    Added in version 244.

ManageForeignRoutingPolicyRules=
    A boolean. When true, systemd-networkd will remove rules that are not configured in .network files (except for rules with protocol "kernel"). When false, it will not remove any foreign rules, keeping them even if they are not configured in a .network file. Defaults to yes.

    Added in version 249.

ManageForeignRoutes=
    A boolean. When true, systemd-networkd will remove routes that are not configured in .network files (except for routes with protocol "kernel", "dhcp" when KeepConfiguration= is true or "dhcp", and "static" when KeepConfiguration= is true or "static"). When false, it will not remove any foreign routes, keeping them even if they are not configured in a .network file. Defaults to yes.

    Added in version 246.

ManageForeignNextHops=
    A boolean. When true, systemd-networkd will remove nexthops that are not configured in .network files (except for routes with protocol "kernel"). When false, it will not remove any foreign nexthops, keeping them even if they are not configured in a .network file. Defaults to yes.

    Added in version 256.

RouteTable=
    Defines the route table name. Takes a whitespace-separated list of the pairs of route table name and number. The route table name and number in each pair are separated with a colon, i.e., "name:number". The route table name must not be "default", "main", or "local", as these route table names are predefined with route table number 253, 254, and 255, respectively. The route table number must be an integer in the range 1...4294967295, except for predefined numbers 253, 254, and 255. This setting can be specified multiple times. If an empty string is specified, then the list specified earlier are cleared. Defaults to unset.

    Added in version 248.

IPv4Forwarding=
    Configures IPv4 packet forwarding for the system. Takes a boolean value. This controls the net.ipv4.conf.default.forwarding and net.ipv4.conf.all.forwarding sysctl options. See IP Sysctl[2] for more details about the sysctl options. Defaults to unset and the sysctl options will not be changed.

    If an interface is configured with a .network file that enables IPMasquerade= for IPv4 (that is, "ipv4" or "both"), this setting is implied unless explicitly specified. See IPMasquerade= in systemd.network(5) for more details.

    Added in version 256.

IPv6Forwarding=
    Configures IPv6 packet forwarding for the system. Takes a boolean value. This controls the net.ipv6.conf.default.forwarding and net.ipv6.conf.all.forwarding sysctl options. See IP Sysctl[2] for more details about the sysctl options. Defaults to unset and the sysctl options will not be changed.

    If an interface is configured with a .network file that enables IPMasquerade= for IPv6 (that is, "ipv6" or "both"), this setting is implied unless explicitly specified. See IPMasquerade= in systemd.network(5) for more details.

    Added in version 256.

IPv6PrivacyExtensions=
    Specifies the default value for per-network IPv6PrivacyExtensions=. Takes a boolean or the special values "prefer-public" and "kernel". See for details in systemd.network(5). Defaults to "no".

    Added in version 254.

UseDomains=
    Specifies the network- and protocol-independent default value for the same settings in [IPv6AcceptRA], [DHCPv4], and [DHCPv6] sections below. Takes a boolean, or the special value route. See the same setting in systemd.network(5). Defaults to "no".

    Added in version 256.

[IPV6ACCEPTRA] SECTION OPTIONS

This section configures the default setting of the Neighbor Discovery. The following options are available in the [IPv6AcceptRA] section:

UseDomains=
    Specifies the network-independent default value for the same setting in the [IPv6AcceptRA] section in systemd.network(5). Takes a boolean, or the special value route. When unspecified, the value specified in the [Network] section in networkd.conf(5), which defaults to "no", will be used.

    Added in version 256.

[IPV6ADDRESSLABEL] SECTION OPTIONS

An [IPv6AddressLabel] section accepts the following keys. Specify multiple [IPv6AddressLabel] sections to configure multiple address labels. IPv6 address labels are used for address selection. See RFC 3484[3]. Precedence is managed by userspace, and only the label itself is stored in the kernel.

Label=
    The label for the prefix, an unsigned integer in the range 0...4294967294. 0xffffffff is reserved. This setting is mandatory.

    Added in version 257.

Prefix=
    IPv6 prefix is an address with a prefix length, separated by a slash "/" character. This setting is mandatory.

    Added in version 257.

[DHCPV4] SECTION OPTIONS

This section configures the default configurations of DHCPv4 client. If the DHCPv4 client is enabled on an interface, then the configurations below will be used by default unless explicitly specified in the corresponding .network file. See also systemd.network(5).

The following options are understood:

ClientIdentifier=
    Specifies the default DHCPv4 client identifier to be used. Takes one of mac or duid. If set to mac, the MAC address of each link will be used. If set to duid, an RFC4361-compliant Client ID, which is the combination of IAID and DUID, is used. IAID can be configured by IAID= in each matching .network file. DUID can be configured by DUIDType= and DUIDRawData=. Defaults to duid.

    Added in version 258.

DUIDType=
    Specifies how the DUID should be generated. See RFC 3315[4] for a description of all the options.

    This takes an integer in the range 0...65535, or one of the following string values:

    vendor
        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.

        Added in version 230.

    uuid
        If "DUIDType=uuid", and DUIDRawData= 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 machine-id(5) is used as a DUID value. About the application-specific machine ID, see sd_id128_get_machine_app_specific(3).

        Added in version 230.

    link-layer-time[:TIME], link-layer
        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".

        Added in version 240.

    In all cases, DUIDRawData= can be used to override the actual DUID value that is used.

    Added in version 230.

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.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[5], RFC 6355[6]. To configure IAID, see systemd.network(5).

    Example 1. A DUIDType=vendor with a custom value

        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". Added in version 230.

UseDomains=
    Same as the one in the [IPv6AcceptRA] section, but applied for DHCPv4 protocol.

    Added in version 256.

[DHCPV6] SECTION OPTIONS

This section configures the default configurations of DHCPv6 client. If the DHCPv6 client is enabled on an interface, then the configurations below will be used by default unless explicitly specified in the corresponding .network file. See also systemd.network(5).

The following options are understood:

DUIDType=, DUIDRawData=
    As in the [DHCPv4] section.

    Added in version 249.

UseDomains=
    As in the [DHCPv4] section.

    Added in version 256.

[DHCPRELAY] SECTION OPTIONS

The [DHCPRelay] section contains host-wide settings for the DHCP relay agent.

ServerAddress=
    Specifies the IPv4 address of the upstream DHCP server. This is required for the host to act as a DHCP relay agent.

    Added in version 261.

OverrideServerIdentifier=
    Takes a boolean value. When enabled, the Server Identifier Override sub-option and the Relay Agent Flags sub-option in the Relay Agent Information option will be appended to the DHCP message forwarded to the upstream DHCP server. Defaults to false.

    Added in version 261.

RemoteId=
    Specifies the remote ID, which is typically used by DHCP servers to identify the DHCP relay agent. Takes a data type and data separated with a colon ("type:value"). The type takes one of "uint8", "uint16", "uint32", "ipv4address", "ipv6address", or "string". Special characters in the data string may be escaped using C-style escapes[7]. If unset, a UUID generated from the local machine ID will be used.

    Added in version 261.

ExtraOption=
    Specifies an extra sub-option in the Relay Agent Information option, which is appended to DHCP messages forwarded to the upstream DHCP server. Takes a sub-option code, data type, and data separated with a colon ("code:type:value"). The code is an integer in 1...254. See RemoteId= in the above for the acceptable type and data. This setting can be specified multiple times. When an empty string is specified, all previous assignments are cleared. Defaults to unset, and no extra sub-option will be appended.

    Added in version 261.

[DHCPSERVER] SECTION OPTIONS

This section configures the default setting of the DHCP server. The following options are available in the [DHCPServer] section:

PersistLeases=
    Specifies the default value for per-network PersistLeases=. Takes a boolean or special value "runtime". See for details in systemd.network(5). Defaults to "yes".

    Added in version 256.

SEE ALSO

systemd(1), systemd.network(5), systemd-networkd.service(8), machine-id(5), sd_id128_get_machine_app_specific(3)

NOTES

1.  💣💥🧨💥💥💣 Please note that those configuration files must be available at all times. If /usr/local/ is a separate partition, it may not be available during early boot, and must not be used for configuration.

2.  IP Sysctl
    https://docs.kernel.org/networking/ip-sysctl.html

3.  RFC 3484
    https://tools.ietf.org/html/rfc3484

4.  RFC 3315
    https://tools.ietf.org/html/rfc3315#section-9

5.  RFC 3315
    http://tools.ietf.org/html/rfc3315#section-9

6.  RFC 6355
    http://tools.ietf.org/html/rfc6355

7.  C-style escapes
    https://en.wikipedia.org/wiki/Escape_sequences_in_C#Table_of_escape_sequences