networkd.conf - Man Page

These configuration files control global network parameters​.

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​.

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​.

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​.

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​.

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​.

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​.

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​.

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​.

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

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