systemd.network(5) - phpMan

SYSTEMD.NETWORK(5) systemd.network SYSTEMD.NETWORK(5)

NAME
systemd.network - Network configuration

SYNOPSIS
network.network

DESCRIPTION
A plain ini-style text file that encodes network configuration for matching network
interfaces, used by systemd-networkd(8). See systemd.syntax(7) for a general description
of the syntax.

The main network file must have the extension .network; other extensions are ignored.
Networks are applied to links whenever the links appear.

The .network files are read from the files located in the system network directories
/lib/systemd/network and /usr/local/lib/systemd/network, the volatile runtime network
directory /run/systemd/network and the local administration network directory
/etc/systemd/network. All configuration files are collectively sorted and processed in
lexical order, regardless of the directories in which they live. However, files with
identical filenames replace each other. Files in /etc/ have the highest priority, files in
/run/ take precedence over files with the same name under /usr/. This can be used to
override a system-supplied configuration file with a local file if needed. As a special
case, an empty file (file size 0) or symlink with the same name pointing to /dev/null
disables the configuration file entirely (it is "masked").

Along with the network file foo.network, a "drop-in" directory foo.network.d/ may exist.
All files with the suffix ".conf" from this directory will be merged in the alphanumeric
order and parsed after the main file itself has been parsed. This is useful to alter or
add configuration settings, without having to modify the main configuration file. Each
drop-in file must have appropriate section headers.

In addition to /etc/systemd/network, drop-in ".d" directories can be placed in
/lib/systemd/network or /run/systemd/network directories. Drop-in files in /etc/ take
precedence over those in /run/ which in turn take precedence over those in /lib/. Drop-in
files under any of these directories take precedence over the main network file wherever
located.

[MATCH] SECTION OPTIONS
The network file contains a [Match] section, which determines if a given network file may
be applied to a given device; and a [Network] section specifying how the device should be
configured. The first (in lexical order) of the network files that matches a given device
is applied, all later files are ignored, even if they match as well.

A network file is said to match a network interface if all matches specified by the
[Match] section are satisfied. When a network file does not contain valid settings in
[Match] section, then the file will match all interfaces and systemd-networkd warns about
that. Hint: to avoid the warning and to make it clear that all interfaces shall be
matched, add the following:

Name=*

The following keys are accepted:

MACAddress=
A whitespace-separated list of hardware addresses. Use full colon-, hyphen- or
dot-delimited hexadecimal. See the example below. This option may appear more than
once, in which case the lists are merged. If the empty string is assigned to this
option, the list of hardware addresses defined prior to this is reset.

Example:

MACAddress=01:23:45:67:89:ab 00-11-22-33-44-55 AABB.CCDD.EEFF

PermanentMACAddress=
A whitespace-separated list of hardware's permanent addresses. While MACAddress=
matches the device's current MAC address, this matches the device's permanent MAC
address, which may be different from the current one. Use full colon-, hyphen- or
dot-delimited hexadecimal. This option may appear more than once, in which case the
lists are merged. If the empty string is assigned to this option, the list of hardware
addresses defined prior to this is reset.

Path=
A whitespace-separated list of shell-style globs matching the persistent path, as
exposed by the udev property ID_PATH.

Driver=
A whitespace-separated list of shell-style globs matching the driver currently bound
to the device, as exposed by the udev property ID_NET_DRIVER of its parent device, or
if that is not set, the driver as exposed by ethtool -i of the device itself. If the
list is prefixed with a "!", the test is inverted.

Type=
A whitespace-separated list of shell-style globs matching the device type, as exposed
by networkctl list. If the list is prefixed with a "!", the test is inverted. Some
valid values are "ether", "loopback", "wlan", "wwan". Valid types are named either
from the udev "DEVTYPE" attribute, or "ARPHRD_" macros in linux/if_arp.h, so this is
not comprehensive.

Property=
A whitespace-separated list of udev property names with their values after equals sign
("="). If multiple properties are specified, the test results are ANDed. If the list
is prefixed with a "!", the test is inverted. If a value contains white spaces, then
please quote whole key and value pair. If a value contains quotation, then please
escape the quotation with "\".

Example: if a .link file has the following:

Property=ID_MODEL_ID=9999 "ID_VENDOR_FROM_DATABASE=vendor name" "KEY=with \"quotation\""

then, the .link file matches only when an interface has all the above three
properties.

Name=
A whitespace-separated list of shell-style globs matching the device name, as exposed
by the udev property "INTERFACE", or device's alternative names. If the list is
prefixed with a "!", the test is inverted.

WLANInterfaceType=
A whitespace-separated list of wireless network type. Supported values are "ad-hoc",
"station", "ap", "ap-vlan", "wds", "monitor", "mesh-point", "p2p-client", "p2p-go",
"p2p-device", "ocb", and "nan". If the list is prefixed with a "!", the test is
inverted.

SSID=
A whitespace-separated list of shell-style globs matching the SSID of the currently
connected wireless LAN. If the list is prefixed with a "!", the test is inverted.

BSSID=
A whitespace-separated list of hardware address of the currently connected wireless
LAN. Use full colon-, hyphen- or dot-delimited hexadecimal. See the example in
MACAddress=. This option may appear more than once, in which case the lists are
merged. If the empty string is assigned to this option, the list is reset.

Host=
Matches against the hostname or machine ID of the host. See ConditionHost= in
systemd.unit(5) for details. When prefixed with an exclamation mark ("!"), the result
is negated. If an empty string is assigned, then previously assigned value is cleared.

Virtualization=
Checks whether the system is executed in a virtualized environment and optionally test
whether it is a specific implementation. See ConditionVirtualization= in
systemd.unit(5) for details. When prefixed with an exclamation mark ("!"), the result
is negated. If an empty string is assigned, then previously assigned value is cleared.

KernelCommandLine=
Checks whether a specific kernel command line option is set. See
ConditionKernelCommandLine= in systemd.unit(5) for details. When prefixed with an
exclamation mark ("!"), the result is negated. If an empty string is assigned, then
previously assigned value is cleared.

KernelVersion=
Checks whether the kernel version (as reported by uname -r) matches a certain
expression. See ConditionKernelVersion= in systemd.unit(5) for details. When prefixed
with an exclamation mark ("!"), the result is negated. If an empty string is assigned,
then previously assigned value is cleared.

Architecture=
Checks whether the system is running on a specific architecture. See
ConditionArchitecture= in systemd.unit(5) for details. When prefixed with an
exclamation mark ("!"), the result is negated. If an empty string is assigned, then
previously assigned value is cleared.

Firmware=
Checks whether the system is running on a machine with the specified firmware. See
ConditionFirmware= in systemd.unit(5) for details. When prefixed with an exclamation
mark ("!"), the result is negated. If an empty string is assigned, then previously
assigned value is cleared.

[LINK] SECTION OPTIONS
The [Link] section accepts the following keys:

MACAddress=
The hardware address to set for the device.

MTUBytes=
The maximum transmission unit in bytes to set for the device. The usual suffixes K, M,
G, are supported and are understood to the base of 1024.

Note that if IPv6 is enabled on the interface, and the MTU is chosen below 1280 (the
minimum MTU for IPv6) it will automatically be increased to this value.

ARP=
Takes a boolean. If set to true, the ARP (low-level Address Resolution Protocol) for
this interface is enabled. When unset, the kernel's default will be used.

For example, disabling ARP is useful when creating multiple MACVLAN or VLAN virtual
interfaces atop a single lower-level physical interface, which will then only serve as
a link/"bridge" device aggregating traffic to the same physical link and not
participate in the network otherwise. Defaults to unset.

Multicast=
Takes a boolean. If set to true, the multicast flag on the device is enabled. Defaults
to unset.

AllMulticast=
Takes a boolean. If set to true, the driver retrieves all multicast packets from the
network. This happens when multicast routing is enabled. Defaults to unset.

Promiscuous=
Takes a boolean. If set to true, promiscuous mode of the interface is enabled.
Defaults to unset.

Unmanaged=
Takes a boolean. When "yes", no attempts are made to bring up or configure matching
links, equivalent to when there are no matching network files. Defaults to "no".

This is useful for preventing later matching network files from interfering with
certain interfaces that are fully controlled by other applications.

Group=
Link groups are similar to port ranges found in managed switches. When network
interfaces are added to a numbered group, operations on all the interfaces from that
group can be performed at once. Takes an unsigned integer in the range 0...4294967295.
Defaults to unset.

RequiredForOnline=
Takes a boolean or a minimum operational state and an optional maximum operational
state. Please see networkctl(1) for possible operational states. When "yes", the
network is deemed required when determining whether the system is online (including
when running systemd-networkd-wait-online). When "no", the network is ignored when
determining the online state. When a minimum operational state and an optional maximum
operational state are set, "yes" is implied, and this controls the minimum and maximum
operational state required for the network interface to be considered online.

Defaults to "yes" when ActivationPolicy= is not set, or set to "up", "always-up", or
"bound". Defaults to "no" when ActivationPolicy= is set to "manual" or "down". This is
forced to "no" when ActivationPolicy= is set to "always-down".

The network will be brought up normally (as configured by ActivationPolicy=), but in
the event that there is no address being assigned by DHCP or the cable is not plugged
in, the link will simply remain offline and be skipped automatically by
systemd-networkd-wait-online if "RequiredForOnline=no".

RequiredFamilyForOnline=
Takes an address family. When specified, an IP address in the given family is deemed
required when determining whether the link is online (including when running
systemd-networkd-wait-online). Takes one of "ipv4", "ipv6", "both", or "any". Defaults
to "any". Note that this option has no effect if "RequiredForOnline=no", or if
"RequiredForOnline=" specifies a minimum operational state below "degraded".

ActivationPolicy=
Specifies the policy for systemd-networkd managing the link administrative state.
Specifically, this controls how systemd-networkd changes the network device's "IFF_UP"
flag, which is sometimes controlled by system administrators by running e.g., ip link
set dev eth0 up or ip link set dev eth0 down, and can also be changed with networkctl
up eth0 or networkctl down eth0.

Takes one of "up", "always-up", "manual", "always-down", "down", or "bound". When
"manual", systemd-networkd will not change the link's admin state automatically; the
system administrator must bring the interface up or down manually, as desired. When
"up" (the default) or "always-up", or "down" or "always-down", systemd-networkd will
set the link up or down, respectively, when the interface is (re)configured. When
"always-up" or "always-down", systemd-networkd will set the link up or down,
respectively, any time systemd-networkd detects a change in the administrative state.
When BindCarrier= is also set, this is automatically set to "bound" and any other
value is ignored.

When the policy is set to "down" or "manual", the default value of RequiredForOnline=
is "no". When the policy is set to "always-down", the value of RequiredForOnline=
forced to "no".

The administrative state is not the same as the carrier state, so using "always-up"
does not mean the link will never lose carrier. The link carrier depends on both the
administrative state as well as the network device's physical connection. However, to
avoid reconfiguration failures, when using "always-up", IgnoreCarrierLoss= is forced
to true.

[SR-IOV] SECTION OPTIONS
The [SR-IOV] section accepts the following keys. Specify several [SR-IOV] sections to
configure several SR-IOVs. SR-IOV provides the ability to partition a single physical PCI
resource into virtual PCI functions which can then be injected into a VM. In the case of
network VFs, SR-IOV improves north-south network performance (that is, traffic with
endpoints outside the host machine) by allowing traffic to bypass the host machine's
network stack.

VirtualFunction=
Specifies a Virtual Function (VF), lightweight PCIe function designed solely to move
data in and out. Takes an unsigned integer in the range 0...2147483646. This option is
compulsory.

VLANId=
Specifies VLAN ID of the virtual function. Takes an unsigned integer in the range
1...4095.

QualityOfService=
Specifies quality of service of the virtual function. Takes an unsigned integer in the
range 1...4294967294.

VLANProtocol=
Specifies VLAN protocol of the virtual function. Takes "802.1Q" or "802.1ad".

MACSpoofCheck=
Takes a boolean. Controls the MAC spoof checking. When unset, the kernel's default
will be used.

QueryReceiveSideScaling=
Takes a boolean. Toggle the ability of querying the receive side scaling (RSS)
configuration of the virtual function (VF). The VF RSS information like RSS hash key
may be considered sensitive on some devices where this information is shared between
VF and the physical function (PF). When unset, the kernel's default will be used.

Trust=
Takes a boolean. Allows to set trust mode of the virtual function (VF). When set, VF
users can set a specific feature which may impact security and/or performance. When
unset, the kernel's default will be used.

LinkState=
Allows to set the link state of the virtual function (VF). Takes a boolean or a
special value "auto". Setting to "auto" means a reflection of the physical function
(PF) link state, "yes" lets the VF to communicate with other VFs on this host even if
the PF link state is down, "no" causes the hardware to drop any packets sent by the
VF. When unset, the kernel's default will be used.

MACAddress=
Specifies the MAC address for the virtual function.

[NETWORK] SECTION OPTIONS
The [Network] section accepts the following keys:

Description=
A description of the device. This is only used for presentation purposes.

DHCP=
Enables DHCPv4 and/or DHCPv6 client support. Accepts "yes", "no", "ipv4", or "ipv6".
Defaults to "no".

Note that DHCPv6 will by default be triggered by Router Advertisement, if that is
enabled, regardless of this parameter. By enabling DHCPv6 support explicitly, the
DHCPv6 client will be started regardless of the presence of routers on the link, or
what flags the routers pass. See "IPv6AcceptRA=".

Furthermore, note that by default the domain name specified through DHCP, on Ubuntu,
are used for name resolution. See option UseDomains= below.

See the [DHCPv4] or [DHCPv6] sections below for further configuration options for the
DHCP client support.

DHCPServer=
Takes a boolean. If set to "yes", DHCPv4 server will be started. Defaults to "no".
Further settings for the DHCP server may be set in the [DHCPServer] section described
below.

LinkLocalAddressing=
Enables link-local address autoconfiguration. Accepts yes, no, ipv4, and ipv6. An IPv6
link-local address is configured when yes or ipv6. An IPv4 link-local address is
configured when yes or ipv4 and when DHCPv4 autoconfiguration has been unsuccessful
for some time. (IPv4 link-local address autoconfiguration will usually happen in
parallel with repeated attempts to acquire a DHCPv4 lease).

Defaults to no when Bridge=yes is set, and ipv6 otherwise.

IPv6LinkLocalAddressGenerationMode=
Specifies how IPv6 link local address is generated. Takes one of "eui64", "none",
"stable-privacy" and "random". When unset, "stable-privacy" is used if
IPv6StableSecretAddress= is specified, and if not, "eui64" is used. Note that if
LinkLocalAddressing= is "no" or "ipv4", then IPv6LinkLocalAddressGenerationMode= will
be ignored. Also, even if LinkLocalAddressing= is "yes" or "ipv6", setting
IPv6LinkLocalAddressGenerationMode=none disables to configure an IPv6 link-local
address.

IPv6StableSecretAddress=
Takes an IPv6 address. The specified address will be used as a stable secret for
generating IPv6 link-local address. If this setting is specified, and
IPv6LinkLocalAddressGenerationMode= is unset, then
IPv6LinkLocalAddressGenerationMode=stable-privacy is implied. If this setting is not
specified, and "stable-privacy" is set to IPv6LinkLocalAddressGenerationMode=, then a
stable secret address will be generated from the local machine ID and the interface
name.

IPv4LLRoute=
Takes a boolean. If set to true, sets up the route needed for non-IPv4LL hosts to
communicate with IPv4LL-only hosts. Defaults to false.

DefaultRouteOnDevice=
Takes a boolean. If set to true, sets up the default route bound to the interface.
Defaults to false. This is useful when creating routes on point-to-point interfaces.
This is equivalent to e.g. the following,

ip route add default dev veth99

or,

[Route]
Gateway=0.0.0.0

Currently, there are no way to specify e.g., the table for the route configured by
this setting. To configure the default route with such an additional property, please
use the following instead:

[Route]
Gateway=0.0.0.0
Table=1234

IPv6Token=
Specifies an optional address generation mode for the Stateless Address
Autoconfiguration (SLAAC). Supported modes are "prefixstable" and "static".

When the mode is set to "static", an IPv6 address must be specified after a colon
(":"), and the lower bits of the supplied address are combined with the upper bits of
a prefix received in a Router Advertisement (RA) message to form a complete address.
Note that if multiple prefixes are received in an RA message, or in multiple RA
messages, addresses will be formed from each of them using the supplied address. This
mode implements SLAAC but uses a static interface identifier instead of an identifier
generated by using the EUI-64 algorithm. Because the interface identifier is static,
if Duplicate Address Detection detects that the computed address is a duplicate (in
use by another node on the link), then this mode will fail to provide an address for
that prefix. If an IPv6 address without mode is specified, then "static" mode is
assumed.

When the mode is set to "prefixstable" the RFC 7217[1] algorithm for generating
interface identifiers will be used. This mode can optionally take an IPv6 address
separated with a colon (":"). If an IPv6 address is specified, then an interface
identifier is generated only when a prefix received in an RA message matches the
supplied address.

If no address generation mode is specified (which is the default), or a received
prefix does not match any of the addresses provided in "prefixstable" mode, then the
EUI-64 algorithm will be used to form an interface identifier for that prefix. This
mode is also SLAAC, but with a potentially stable interface identifier which does not
directly map to the interface's hardware address.

Note that the "prefixstable" algorithm uses both the interface name and MAC address as
input to the hash to compute the interface identifier, so if either of those are
changed the resulting interface identifier (and address) will change, even if the
prefix received in the RA message has not changed.

This setting can be specified multiple times. If an empty string is assigned, then the
all previous assignments are cleared.

Examples:

IPv6Token=::1a:2b:3c:4d
IPv6Token=static:::1a:2b:3c:4d
IPv6Token=prefixstable
IPv6Token=prefixstable:2002:da8:1::

LLMNR=
Takes a boolean or "resolve". When true, enables Link-Local Multicast Name
Resolution[2] on the link. When set to "resolve", only resolution is enabled, but not
host registration and announcement. Defaults to true. This setting is read by systemd-
resolved.service(8).

MulticastDNS=
Takes a boolean or "resolve". When true, enables Multicast DNS[3] support on the link.
When set to "resolve", only resolution is enabled, but not host or service
registration and announcement. Defaults to false. This setting is read by systemd-
resolved.service(8).

DNSOverTLS=
Takes a boolean or "opportunistic". When true, enables DNS-over-TLS[4] support on the
link. When set to "opportunistic", compatibility with non-DNS-over-TLS servers is
increased, by automatically turning off DNS-over-TLS servers in this case. This option
defines a per-interface setting for resolved.conf(5)'s global DNSOverTLS= option.
Defaults to false. This setting is read by systemd-resolved.service(8).

DNSSEC=
Takes a boolean or "allow-downgrade". When true, enables DNSSEC[5] DNS validation
support on the link. When set to "allow-downgrade", compatibility with non-DNSSEC
capable networks is increased, by automatically turning off DNSSEC in this case. This
option defines a per-interface setting for resolved.conf(5)'s global DNSSEC= option.
Defaults to false. This setting is read by systemd-resolved.service(8).

DNSSECNegativeTrustAnchors=
A space-separated list of DNSSEC negative trust anchor domains. If specified and
DNSSEC is enabled, look-ups done via the interface's DNS server will be subject to the
list of negative trust anchors, and not require authentication for the specified
domains, or anything below it. Use this to disable DNSSEC authentication for specific
private domains, that cannot be proven valid using the Internet DNS hierarchy.
Defaults to the empty list. This setting is read by systemd-resolved.service(8).

LLDP=
Controls support for Ethernet LLDP packet reception. LLDP is a link-layer protocol
commonly implemented on professional routers and bridges which announces which
physical port a system is connected to, as well as other related data. Accepts a
boolean or the special value "routers-only". When true, incoming LLDP packets are
accepted and a database of all LLDP neighbors maintained. If "routers-only" is set
only LLDP data of various types of routers is collected and LLDP data about other
types of devices ignored (such as stations, telephones and others). If false, LLDP
reception is disabled. Defaults to "routers-only". Use networkctl(1) to query the
collected neighbor data. LLDP is only available on Ethernet links. See EmitLLDP= below
for enabling LLDP packet emission from the local system.

EmitLLDP=
Controls support for Ethernet LLDP packet emission. Accepts a boolean parameter or the
special values "nearest-bridge", "non-tpmr-bridge" and "customer-bridge". Defaults to
false, which turns off LLDP packet emission. If not false, a short LLDP packet with
information about the local system is sent out in regular intervals on the link. The
LLDP packet will contain information about the local hostname, the local machine ID
(as stored in machine-id(5)) and the local interface name, as well as the pretty
hostname of the system (as set in machine-info(5)). LLDP emission is only available on
Ethernet links. Note that this setting passes data suitable for identification of host
to the network and should thus not be enabled on untrusted networks, where such
identification data should not be made available. Use this option to permit other
systems to identify on which interfaces they are connected to this system. The three
special values control propagation of the LLDP packets. The "nearest-bridge" setting
permits propagation only to the nearest connected bridge, "non-tpmr-bridge" permits
propagation across Two-Port MAC Relays, but not any other bridges, and
"customer-bridge" permits propagation until a customer bridge is reached. For details
about these concepts, see IEEE 802.1AB-2016[6]. Note that configuring this setting to
true is equivalent to "nearest-bridge", the recommended and most restricted level of
propagation. See LLDP= above for an option to enable LLDP reception.

BindCarrier=
A link name or a list of link names. When set, controls the behavior of the current
link. When all links in the list are in an operational down state, the current link is
brought down. When at least one link has carrier, the current interface is brought up.

This forces ActivationPolicy= to be set to "bound".

Address=
A static IPv4 or IPv6 address and its prefix length, separated by a "/" character.
Specify this key more than once to configure several addresses. The format of the
address must be as described in inet_pton(3). This is a short-hand for an [Address]
section only containing an Address key (see below). This option may be specified more
than once.

If the specified address is "0.0.0.0" (for IPv4) or "::" (for IPv6), a new address
range of the requested size is automatically allocated from a system-wide pool of
unused ranges. Note that the prefix length must be equal or larger than 8 for IPv4,
and 64 for IPv6. The allocated range is checked against all current network interfaces
and all known network configuration files to avoid address range conflicts. The
default system-wide pool consists of 192.168.0.0/16, 172.16.0.0/12 and 10.0.0.0/8 for
IPv4, and fd00::/8 for IPv6. This functionality is useful to manage a large number of
dynamically created network interfaces with the same network configuration and
automatic address range assignment.

Gateway=
The gateway address, which must be in the format described in inet_pton(3). This is a
short-hand for a [Route] section only containing a Gateway key. This option may be
specified more than once.

DNS=
A DNS server address, which must be in the format described in inet_pton(3). This
option may be specified more than once. Each address can optionally take a port number
separated with ":", a network interface name or index separated with "%", and a Server
Name Indication (SNI) separated with "#". When IPv6 address is specified with a port
number, then the address must be in the square brackets. That is, the acceptable full
formats are "111.222.333.444:9953%ifname#example.com" for IPv4 and
"[1111:2222::3333]:9953%ifname#example.com" for IPv6. If an empty string is assigned,
then the all previous assignments are cleared. This setting is read by systemd-
resolved.service(8).

Domains=
A whitespace-separated list of domains which should be resolved using the DNS servers
on this link. Each item in the list should be a domain name, optionally prefixed with
a tilde ("~"). The domains with the prefix are called "routing-only domains". The
domains without the prefix are called "search domains" and are first used as search
suffixes for extending single-label hostnames (hostnames containing no dots) to become
fully qualified domain names (FQDNs). If a single-label hostname is resolved on this
interface, each of the specified search domains are appended to it in turn, converting
it into a fully qualified domain name, until one of them may be successfully resolved.

Both "search" and "routing-only" domains are used for routing of DNS queries: look-ups
for hostnames ending in those domains (hence also single label names, if any "search
domains" are listed), are routed to the DNS servers configured for this interface. The
domain routing logic is particularly useful on multi-homed hosts with DNS servers
serving particular private DNS zones on each interface.

The "routing-only" domain "~." (the tilde indicating definition of a routing domain,
the dot referring to the DNS root domain which is the implied suffix of all valid DNS
names) has special effect. It causes all DNS traffic which does not match another
configured domain routing entry to be routed to DNS servers specified for this
interface. This setting is useful to prefer a certain set of DNS servers if a link on
which they are connected is available.

This setting is read by systemd-resolved.service(8). "Search domains" correspond to
the domain and search entries in resolv.conf(5). Domain name routing has no equivalent
in the traditional glibc API, which has no concept of domain name servers limited to a
specific link.

DNSDefaultRoute=
Takes a boolean argument. If true, this link's configured DNS servers are used for
resolving domain names that do not match any link's configured Domains= setting. If
false, this link's configured DNS servers are never used for such domains, and are
exclusively used for resolving names that match at least one of the domains configured
on this link. If not specified defaults to an automatic mode: queries not matching any
link's configured domains will be routed to this link if it has no routing-only
domains configured.

NTP=
An NTP server address (either an IP address, or a hostname). This option may be
specified more than once. This setting is read by systemd-timesyncd.service(8).

IPForward=
Configures IP packet forwarding for the system. If enabled, incoming packets on any
network interface will be forwarded to any other interfaces according to the routing
table. Takes a boolean, or the values "ipv4" or "ipv6", which only enable IP packet
forwarding for the specified address family. This controls the net.ipv4.ip_forward and
net.ipv6.conf.all.forwarding sysctl options of the network interface (see
ip-sysctl.txt[7] for details about sysctl options). Defaults to "no".

Note: this setting controls a global kernel option, and does so one way only: if a
network that has this setting enabled is set up the global setting is turned on.
However, it is never turned off again, even after all networks with this setting
enabled are shut down again.

To allow IP packet forwarding only between specific network interfaces use a firewall.

IPMasquerade=
Configures IP masquerading for the network interface. If enabled, packets forwarded
from the network interface will be appear as coming from the local host. Takes one of
"ipv4", "ipv6", "both", or "no". Defaults to "no". If enabled, this automatically sets
IPForward= to one of "ipv4", "ipv6" or "yes".

Note. Any positive boolean values such as "yes" or "true" are now deprecated. Please
use one of the values in the above.

IPv6PrivacyExtensions=
Configures use of stateless temporary addresses that change over time (see RFC
4941[8], Privacy Extensions for Stateless Address Autoconfiguration in IPv6). Takes a
boolean or the special values "prefer-public" and "kernel". When true, enables the
privacy extensions and prefers temporary addresses over public addresses. When
"prefer-public", enables the privacy extensions, but prefers public addresses over
temporary addresses. When false, the privacy extensions remain disabled. When
"kernel", the kernel's default setting will be left in place. Defaults to "no".

IPv6AcceptRA=
Takes a boolean. Controls IPv6 Router Advertisement (RA) reception support for the
interface. If true, RAs are accepted; if false, RAs are ignored. When RAs are
accepted, they may trigger the start of the DHCPv6 client if the relevant flags are
set in the RA data, or if no routers are found on the link. The default is to disable
RA reception for bridge devices or when IP forwarding is enabled, and to enable it
otherwise. Cannot be enabled on bond devices and when link local addressing is
disabled.

Further settings for the IPv6 RA support may be configured in the [IPv6AcceptRA]
section, see below.

Also see ip-sysctl.txt[7] in the kernel documentation regarding "accept_ra", but note
that systemd's setting of 1 (i.e. true) corresponds to kernel's setting of 2.

Note that kernel's implementation of the IPv6 RA protocol is always disabled,
regardless of this setting. If this option is enabled, a userspace implementation of
the IPv6 RA protocol is used, and the kernel's own implementation remains disabled,
since systemd-networkd needs to know all details supplied in the advertisements, and
these are not available from the kernel if the kernel's own implementation is used.

IPv6DuplicateAddressDetection=
Configures the amount of IPv6 Duplicate Address Detection (DAD) probes to send. When
unset, the kernel's default will be used.

IPv6HopLimit=
Configures IPv6 Hop Limit. For each router that forwards the packet, the hop limit is
decremented by 1. When the hop limit field reaches zero, the packet is discarded. When
unset, the kernel's default will be used.

IPv4AcceptLocal=
Takes a boolean. Accept packets with local source addresses. In combination with
suitable routing, this can be used to direct packets between two local interfaces over
the wire and have them accepted properly. When unset, the kernel's default will be
used.

IPv4RouteLocalnet=
Takes a boolean. When true, the kernel does not consider loopback addresses as martian
source or destination while routing. This enables the use of 127.0.0.0/8 for local
routing purposes. When unset, the kernel's default will be used.

IPv4ProxyARP=
Takes a boolean. Configures proxy ARP for IPv4. Proxy ARP is the technique in which
one host, usually a router, answers ARP requests intended for another machine. By
"faking" its identity, the router accepts responsibility for routing packets to the
"real" destination. See RFC 1027[9]. When unset, the kernel's default will be used.

IPv6ProxyNDP=
Takes a boolean. Configures proxy NDP for IPv6. Proxy NDP (Neighbor Discovery
Protocol) is a technique for IPv6 to allow routing of addresses to a different
destination when peers expect them to be present on a certain physical link. In this
case a router answers Neighbour Advertisement messages intended for another machine by
offering its own MAC address as destination. Unlike proxy ARP for IPv4, it is not
enabled globally, but will only send Neighbour Advertisement messages for addresses in
the IPv6 neighbor proxy table, which can also be shown by ip -6 neighbour show proxy.
systemd-networkd will control the per-interface `proxy_ndp` switch for each configured
interface depending on this option. When unset, the kernel's default will be used.

IPv6ProxyNDPAddress=
An IPv6 address, for which Neighbour Advertisement messages will be proxied. This
option may be specified more than once. systemd-networkd will add the
IPv6ProxyNDPAddress= entries to the kernel's IPv6 neighbor proxy table. This option
implies IPv6ProxyNDP=yes but has no effect if IPv6ProxyNDP has been set to false. When
unset, the kernel's default will be used.

IPv6SendRA=
Whether to enable or disable Router Advertisement sending on a link. Takes a boolean
value. When enabled, prefixes configured in [IPv6Prefix] sections and routes
configured in [IPv6RoutePrefix] sections are distributed as defined in the
[IPv6SendRA] section. If DHCPv6PrefixDelegation= is enabled, then the delegated
prefixes are also distributed. See DHCPv6PrefixDelegation= setting and the
[IPv6SendRA], [IPv6Prefix], [IPv6RoutePrefix], and [DHCPv6PrefixDelegation] sections
for more configuration options.

DHCPv6PrefixDelegation=
Takes a boolean value. When enabled, requests prefixes using a DHCPv6 client
configured on another link. By default, an address within each delegated prefix will
be assigned, and the prefixes will be announced through IPv6 Router Advertisement when
IPv6SendRA= is enabled. Such default settings can be configured in
[DHCPv6PrefixDelegation] section. Defaults to disabled.

IPv6MTUBytes=
Configures IPv6 maximum transmission unit (MTU). An integer greater than or equal to
1280 bytes. When unset, the kernel's default will be used.

BatmanAdvanced=, Bond=, Bridge=, VRF=
The name of the B.A.T.M.A.N. Advanced, bond, bridge, or VRF interface to add the link
to. See systemd.netdev(5).

IPVLAN=, IPVTAP=, L2TP=, MACsec=, MACVLAN=, MACVTAP=, Tunnel=, VLAN=, VXLAN=, Xfrm=
The name of an IPVLAN, IPVTAP, L2TP, MACsec, MACVLAN, MACVTAP, tunnel, VLAN, VXLAN, or
Xfrm to be created on the link. See systemd.netdev(5). This option may be specified
more than once.

ActiveSlave=
Takes a boolean. Specifies the new active slave. The "ActiveSlave=" option is only
valid for following modes: "active-backup", "balance-alb" and "balance-tlb". Defaults
to false.

PrimarySlave=
Takes a boolean. Specifies which slave is the primary device. The specified device
will always be the active slave while it is available. Only when the primary is
off-line will alternate devices be used. This is useful when one slave is preferred
over another, e.g. when one slave has higher throughput than another. The
"PrimarySlave=" option is only valid for following modes: "active-backup",
"balance-alb" and "balance-tlb". Defaults to false.

ConfigureWithoutCarrier=
Takes a boolean. Allows networkd to configure a specific link even if it has no
carrier. Defaults to false. If IgnoreCarrierLoss= is not explicitly set, it will
default to this value.

IgnoreCarrierLoss=
Takes a boolean. Allows networkd to retain both the static and dynamic configuration
of the interface even if its carrier is lost. When unset, the value specified with
ConfigureWithoutCarrier= is used.

When ActivationPolicy= is set to "always-up", this is forced to "true".

KeepConfiguration=
Takes a boolean or one of "static", "dhcp-on-stop", "dhcp". When "static",
systemd-networkd will not drop static addresses and routes on starting up process.
When set to "dhcp-on-stop", systemd-networkd will not drop addresses and routes on
stopping the daemon. When "dhcp", the addresses and routes provided by a DHCP server
will never be dropped even if the DHCP lease expires. This is contrary to the DHCP
specification, but may be the best choice if, e.g., the root filesystem relies on this
connection. The setting "dhcp" implies "dhcp-on-stop", and "yes" implies "dhcp" and
"static". Defaults to "no".

[ADDRESS] SECTION OPTIONS
An [Address] section accepts the following keys. Specify several [Address] sections to
configure several addresses.

Address=
As in the [Network] section. This key is mandatory. Each [Address] section can contain
one Address= setting.

Peer=
The peer address in a point-to-point connection. Accepts the same format as the
Address= key.

Broadcast=
Takes an IPv4 address or boolean value. The address must be in the format described in
inet_pton(3). If set to true, then the IPv4 broadcast address will be derived from the
Address= setting. If set to false, then the broadcast address will not be set.
Defaults to true, except for wireguard interfaces, where it default to false.

Label=
An address label.

PreferredLifetime=
Allows the default "preferred lifetime" of the address to be overridden. Only three
settings are accepted: "forever", "infinity", which is the default and means that the
address never expires, and "0", which means that the address is considered immediately
"expired" and will not be used, unless explicitly requested. A setting of
PreferredLifetime=0 is useful for addresses which are added to be used only by a
specific application, which is then configured to use them explicitly.

Scope=
The scope of the address, which can be "global" (valid everywhere on the network, even
through a gateway), "link" (only valid on this device, will not traverse a gateway) or
"host" (only valid within the device itself, e.g. 127.0.0.1) or an unsigned integer in
the range 0...255. Defaults to "global".

RouteMetric=
The metric of the prefix route, which is pointing to the subnet of the configured IP
address, taking the configured prefix length into account. Takes an unsigned integer
in the range 0...4294967295. When unset or set to 0, the kernel's default value is
used. This setting will be ignored when AddPrefixRoute= is false.

HomeAddress=
Takes a boolean. Designates this address the "home address" as defined in RFC
6275[10]. Supported only on IPv6. Defaults to false.

DuplicateAddressDetection=
Takes one of "ipv4", "ipv6", "both", "none". When "ipv4", performs IPv4 Address
Conflict Detection. See RFC 5227[11]. When "ipv6", performs IPv6 Duplicate Address
Detection. See RFC 4862[12]. Defaults to "ipv4" for IPv4 link-local addresses, "ipv6"
for IPv6 addresses, and "none" otherwise.

ManageTemporaryAddress=
Takes a boolean. If true the kernel manage temporary addresses created from this one
as template on behalf of Privacy Extensions RFC 3041[13]. For this to become active,
the use_tempaddr sysctl setting has to be set to a value greater than zero. The given
address needs to have a prefix length of 64. This flag allows using privacy extensions
in a manually configured network, just like if stateless auto-configuration was
active. Defaults to false.

AddPrefixRoute=
Takes a boolean. When true, the prefix route for the address is automatically added.
Defaults to true.

AutoJoin=
Takes a boolean. Joining multicast group on ethernet level via ip maddr command would
not work if we have an Ethernet switch that does IGMP snooping since the switch would
not replicate multicast packets on ports that did not have IGMP reports for the
multicast addresses. Linux vxlan interfaces created via ip link add vxlan or
networkd's netdev kind vxlan have the group option that enables then to do the
required join. By extending ip address command with option "autojoin" we can get
similar functionality for openvswitch (OVS) vxlan interfaces as well as other
tunneling mechanisms that need to receive multicast traffic. Defaults to "no".

[NEIGHBOR] SECTION OPTIONS
A [Neighbor] section accepts the following keys. The neighbor section adds a permanent,
static entry to the neighbor table (IPv6) or ARP table (IPv4) for the given hardware
address on the links matched for the network. Specify several [Neighbor] sections to
configure several static neighbors.

Address=
The IP address of the neighbor.

LinkLayerAddress=
The link layer address (MAC address or IP address) of the neighbor.

[IPV6ADDRESSLABEL] SECTION OPTIONS
An [IPv6AddressLabel] section accepts the following keys. Specify several
[IPv6AddressLabel] sections to configure several address labels. IPv6 address labels are
used for address selection. See RFC 3484[14]. 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.

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

[ROUTINGPOLICYRULE] SECTION OPTIONS
An [RoutingPolicyRule] section accepts the following keys. Specify several
[RoutingPolicyRule] sections to configure several rules.

TypeOfService=
Takes a number between 0 and 255 that specifies the type of service to match.

From=
Specifies the source address prefix to match. Possibly followed by a slash and the
prefix length.

To=
Specifies the destination address prefix to match. Possibly followed by a slash and
the prefix length.

FirewallMark=
Specifies the iptables firewall mark value to match (a number between 1 and
4294967295). Optionally, the firewall mask (also a number between 1 and 4294967295)
can be suffixed with a slash ("/"), e.g., "7/255".

Table=
Specifies the routing table identifier to lookup if the rule selector matches. Takes
one of predefined names "default", "main", and "local", and names defined in
RouteTable= in networkd.conf(5), or a number between 1 and 4294967295. Defaults to
"main".

Priority=
Specifies the priority of this rule. Priority= is an unsigned integer in the range
0...4294967295. Higher number means lower priority, and rules get processed in order
of increasing number. Defaults to unset, and the kernel will pick a value dynamically.

IncomingInterface=
Specifies incoming device to match. If the interface is loopback, the rule only
matches packets originating from this host.

OutgoingInterface=
Specifies the outgoing device to match. The outgoing interface is only available for
packets originating from local sockets that are bound to a device.

SourcePort=
Specifies the source IP port or IP port range match in forwarding information base
(FIB) rules. A port range is specified by the lower and upper port separated by a
dash. Defaults to unset.

DestinationPort=
Specifies the destination IP port or IP port range match in forwarding information
base (FIB) rules. A port range is specified by the lower and upper port separated by a
dash. Defaults to unset.

IPProtocol=
Specifies the IP protocol to match in forwarding information base (FIB) rules. Takes
IP protocol name such as "tcp", "udp" or "sctp", or IP protocol number such as "6" for
"tcp" or "17" for "udp". Defaults to unset.

InvertRule=
A boolean. Specifies whether the rule is to be inverted. Defaults to false.

Family=
Takes a special value "ipv4", "ipv6", or "both". By default, the address family is
determined by the address specified in To= or From=. If neither To= nor From= are
specified, then defaults to "ipv4".

User=
Takes a username, a user ID, or a range of user IDs separated by a dash. Defaults to
unset.

SuppressPrefixLength=
Takes a number N in the range 0...128 and rejects routing decisions that have a prefix
length of N or less. Defaults to unset.

Type=
Specifies Routing Policy Database (RPDB) rule type. Takes one of "blackhole",
"unreachable" or "prohibit".

[NEXTHOP] SECTION OPTIONS
The [NextHop] section is used to manipulate entries in the kernel's "nexthop" tables. The
[NextHop] section accepts the following keys. Specify several [NextHop] sections to
configure several hops.

Id=
The id of the next hop. Takes an unsigned integer in the range 1...4294967295. If left
unspecified, then automatically chosen by kernel.

Gateway=
As in the [Network] section.

Family=
Takes one of the special values "ipv4" or "ipv6". By default, the family is determined
by the address specified in Gateway=. If Gateway= is not specified, then defaults to
"ipv4".

OnLink=
Takes a boolean. If set to true, the kernel does not have to check if the gateway is
reachable directly by the current machine (i.e., attached to the local network), so
that we can insert the nexthop in the kernel table without it being complained about.
Defaults to "no".

Blackhole=
Takes a boolean. If enabled, packets to the corresponding routes are discarded
silently, and Gateway= cannot be specified. Defaults to "no".

Group=
Takes a whitespace separated list of nexthop IDs. Each ID must be in the range
1...4294967295. Optionally, each nexthop ID can take a weight after a colon
("id[:weight]"). The weight must be in the range 1...255. If the weight is not
specified, then it is assumed that the weight is 1. This setting cannot be specified
with Gateway=, Family=, Blackhole=. This setting can be specified multiple times. If
an empty string is assigned, then the all previous assignments are cleared. Defaults
to unset.

[ROUTE] SECTION OPTIONS
The [Route] section accepts the following keys. Specify several [Route] sections to
configure several routes.

Gateway=
Takes the gateway address or the special values "_dhcp4" and "_ipv6ra". If "_dhcp4" or
"_ipv6ra" is set, then the gateway address provided by DHCPv4 or IPv6 RA is used.

GatewayOnLink=
Takes a boolean. If set to true, the kernel does not have to check if the gateway is
reachable directly by the current machine (i.e., attached to the local network), so
that we can insert the route in the kernel table without it being complained about.
Defaults to "no".

Destination=
The destination prefix of the route. Possibly followed by a slash and the prefix
length. If omitted, a full-length host route is assumed.

Source=
The source prefix of the route. Possibly followed by a slash and the prefix length. If
omitted, a full-length host route is assumed.

Metric=
The metric of the route. Takes an unsigned integer in the range 0...4294967295.
Defaults to unset, and the kernel's default will be used.

IPv6Preference=
Specifies the route preference as defined in RFC 4191[15] for Router Discovery
messages. Which can be one of "low" the route has a lowest priority, "medium" the
route has a default priority or "high" the route has a highest priority.

Scope=
The scope of the IPv4 route, which can be "global", "site", "link", "host", or
"nowhere":

o "global" means the route can reach hosts more than one hop away.

o "site" means an interior route in the local autonomous system.

o "link" means the route can only reach hosts on the local network (one hop away).

o "host" means the route will not leave the local machine (used for internal
addresses like 127.0.0.1).

o "nowhere" means the destination doesn't exist.

For IPv4 route, defaults to "host" if Type= is "local" or "nat", and "link" if Type=
is "broadcast", "multicast", or "anycast". In other cases, defaults to "global". The
value is not used for IPv6.

PreferredSource=
The preferred source address of the route. The address must be in the format described
in inet_pton(3).

Table=
The table identifier for the route. Takes one of predefined names "default", "main",
and "local", and names defined in RouteTable= in networkd.conf(5), or a number between
1 and 4294967295. The table can be retrieved using ip route show table num. If unset
and Type= is "local", "broadcast", "anycast", or "nat", then "local" is used. In other
cases, defaults to "main".

Protocol=
The protocol identifier for the route. Takes a number between 0 and 255 or the special
values "kernel", "boot", "static", "ra" and "dhcp". Defaults to "static".

Type=
Specifies the type for the route. Takes one of "unicast", "local", "broadcast",
"anycast", "multicast", "blackhole", "unreachable", "prohibit", "throw", "nat", and
"xresolve". If "unicast", a regular route is defined, i.e. a route indicating the path
to take to a destination network address. If "blackhole", packets to the defined route
are discarded silently. If "unreachable", packets to the defined route are discarded
and the ICMP message "Host Unreachable" is generated. If "prohibit", packets to the
defined route are discarded and the ICMP message "Communication Administratively
Prohibited" is generated. If "throw", route lookup in the current routing table will
fail and the route selection process will return to Routing Policy Database (RPDB).
Defaults to "unicast".

InitialCongestionWindow=
The TCP initial congestion window is used during the start of a TCP connection. During
the start of a TCP session, when a client requests a resource, the server's initial
congestion window determines how many packets will be sent during the initial burst of
data without waiting for acknowledgement. Takes a number between 1 and 1023. Note that
100 is considered an extremely large value for this option. When unset, the kernel's
default (typically 10) will be used.

InitialAdvertisedReceiveWindow=
The TCP initial advertised receive window is the amount of receive data (in bytes)
that can initially be buffered at one time on a connection. The sending host can send
only that amount of data before waiting for an acknowledgment and window update from
the receiving host. Takes a number between 1 and 1023. Note that 100 is considered an
extremely large value for this option. When unset, the kernel's default will be used.

QuickAck=
Takes a boolean. When true enables TCP quick ack mode for the route. When unset, the
kernel's default will be used.

FastOpenNoCookie=
Takes a boolean. When true enables TCP fastopen without a cookie on a per-route basis.
When unset, the kernel's default will be used.

TTLPropagate=
Takes a boolean. When true enables TTL propagation at Label Switched Path (LSP)
egress. When unset, the kernel's default will be used.

MTUBytes=
The maximum transmission unit in bytes to set for the route. The usual suffixes K, M,
G, are supported and are understood to the base of 1024.

Note that if IPv6 is enabled on the interface, and the MTU is chosen below 1280 (the
minimum MTU for IPv6) it will automatically be increased to this value.

IPServiceType=
Takes string; "CS6" or "CS4". Used to set IP service type to CS6 (network control) or
CS4 (Realtime). Defaults to CS6.

TCPAdvertisedMaximumSegmentSize=
Specifies the Path MSS (in bytes) hints given on TCP layer. The usual suffixes K, M,
G, are supported and are understood to the base of 1024. An unsigned integer in the
range 1-4294967294. When unset, the kernel's default will be used.

MultiPathRoute=address[@name] [weight]
Configures multipath route. Multipath routing is the technique of using multiple
alternative paths through a network. Takes gateway address. Optionally, takes a
network interface name or index separated with "@", and a weight in 1..256 for this
multipath route separated with whitespace. This setting can be specified multiple
times. If an empty string is assigned, then the all previous assignments are cleared.

NextHop=
Specifies the nexthop id. Takes an unsigned integer in the range 1...4294967295. If
set, the corresponding [NextHop] section must be configured. Defaults to unset.

[DHCPV4] SECTION OPTIONS
The [DHCPv4] section configures the DHCPv4 client, if it is enabled with the DHCP= setting
described above:

SendHostname=
When true (the default), the machine's hostname (or the value specified with
Hostname=, described below) will be sent to the DHCP server. Note that the hostname
must consist only of 7-bit ASCII lower-case characters and no spaces or dots, and be
formatted as a valid DNS domain name. Otherwise, the hostname is not sent even if this
option is true.

Hostname=
Use this value for the hostname which is sent to the DHCP server, instead of machine's
hostname. Note that the specified hostname must consist only of 7-bit ASCII lower-case
characters and no spaces or dots, and be formatted as a valid DNS domain name.

MUDURL=
When configured, the specified Manufacturer Usage Description (MUD) URL will be sent
to the DHCPv4 server. Takes a URL of length up to 255 characters. A superficial
verification that the string is a valid URL will be performed. DHCPv4 clients are
intended to have at most one MUD URL associated with them. See RFC 8520[16].

MUD is an embedded software standard defined by the IETF that allows IoT device makers
to advertise device specifications, including the intended communication patterns for
their device when it connects to the network. The network can then use this to author
a context-specific access policy, so the device functions only within those
parameters.

ClientIdentifier=
The DHCPv4 client identifier to use. Takes one of mac, duid or duid-only. If set to
mac, the MAC address of the link is used. If set to duid, an RFC4361-compliant Client
ID, which is the combination of IAID and DUID (see below), is used. If set to
duid-only, only DUID is used, this may not be RFC compliant, but some setups may
require to use this. Defaults to duid.

VendorClassIdentifier=
The vendor class identifier used to identify vendor type and configuration.

UserClass=
A DHCPv4 client can use UserClass option to identify the type or category of user or
applications it represents. The information contained in this option is a string that
represents the user class of which the client is a member. Each class sets an
identifying string of information to be used by the DHCP service to classify clients.
Takes a whitespace-separated list of strings.

DUIDType=
Override the global DUIDType= setting for this network. See networkd.conf(5) for a
description of possible values.

DUIDRawData=
Override the global DUIDRawData= setting for this network. See networkd.conf(5) for a
description of possible values.

IAID=
The DHCP Identity Association Identifier (IAID) for the interface, a 32-bit unsigned
integer.

Anonymize=
Takes a boolean. When true, the options sent to the DHCP server will follow the RFC
7844[17] (Anonymity Profiles for DHCP Clients) to minimize disclosure of identifying
information. Defaults to false.

This option should only be set to true when MACAddressPolicy= is set to random (see
systemd.link(5)).

When true, SendHostname=, ClientIdentifier=, VendorClassIdentifier=, UserClass=,
RequestOptions=, SendOption=, SendVendorOption=, and MUDURL= are ignored.

With this option enabled DHCP requests will mimic those generated by Microsoft
Windows, in order to reduce the ability to fingerprint and recognize installations.
This means DHCP request sizes will grow and lease data will be more comprehensive than
normally, though most of the requested data is not actually used.

RequestOptions=
Sets request options to be sent to the server in the DHCPv4 request options list. A
whitespace-separated list of integers in the range 1...254. Defaults to unset.

SendOption=
Send an arbitrary raw option in the DHCPv4 request. Takes a DHCP option number, data
type and data separated with a colon ("option:type:value"). The option number must be
an integer in the range 1...254. The type takes one of "uint8", "uint16", "uint32",
"ipv4address", or "string". Special characters in the data string may be escaped using
C-style escapes[18]. This setting can be specified multiple times. If an empty string
is specified, then all options specified earlier are cleared. Defaults to unset.

SendVendorOption=
Send an arbitrary vendor option in the DHCPv4 request. Takes a DHCP option number,
data type and data separated with a colon ("option:type:value"). The option number
must be an integer in the range 1...254. The type takes one of "uint8", "uint16",
"uint32", "ipv4address", or "string". Special characters in the data string may be
escaped using C-style escapes[18]. This setting can be specified multiple times. If an
empty string is specified, then all options specified earlier are cleared. Defaults to
unset.

UseDNS=
When true (the default), the DNS servers received from the DHCP server will be used.

This corresponds to the nameserver option in resolv.conf(5).

RoutesToDNS=
When true, the routes to the DNS servers received from the DHCP server will be
configured. When UseDNS= is disabled, this setting is ignored. Defaults to true.

UseNTP=
When true (the default), the NTP servers received from the DHCP server will be used by
systemd-timesyncd.service.

RoutesToNTP=
When true, the routes to the NTP servers received from the DHCP server will be
configured. When UseNTP= is disabled, this setting is ignored. Defaults to true.

UseSIP=
When true (the default), the SIP servers received from the DHCP server will be
collected and made available to client programs.

UseMTU=
When true, the interface maximum transmission unit from the DHCP server will be used
on the current link. If MTUBytes= is set, then this setting is ignored. Defaults to
false.

UseHostname=
When true (the default), the hostname received from the DHCP server will be set as the
transient hostname of the system.

UseDomains=
Takes a boolean, or the special value route. When true, the domain name received from
the DHCP server will be used as DNS search domain over this link, similar to the
effect of the Domains= setting. If set to route, the domain name received from the
DHCP server will be used for routing DNS queries only, but not for searching, similar
to the effect of the Domains= setting when the argument is prefixed with "~". Defaults
to true on Ubuntu.

It is recommended to enable this option only on trusted networks, as setting this
affects resolution of all hostnames, in particular of single-label names. It is
generally safer to use the supplied domain only as routing domain, rather than as
search domain, in order to not have it affect local resolution of single-label names.

When set to true, this setting corresponds to the domain option in resolv.conf(5).

UseRoutes=
When true (the default), the static routes will be requested from the DHCP server and
added to the routing table with a metric of 1024, and a scope of global, link or host,
depending on the route's destination and gateway. If the destination is on the local
host, e.g., 127.x.x.x, or the same as the link's own address, the scope will be set to
host. Otherwise if the gateway is null (a direct route), a link scope will be used.
For anything else, scope defaults to global.

RouteMetric=
Set the routing metric for routes specified by the DHCP server. Takes an unsigned
integer in the range 0...4294967295. Defaults to 1024.

RouteTable=num
The table identifier for DHCP routes (a number between 1 and 4294967295, or 0 to
unset). The table can be retrieved using ip route show table num.

When used in combination with VRF=, the VRF's routing table is used when this
parameter is not specified.

RouteMTUBytes=
Specifies the MTU for the DHCP routes. Please see the [Route] section for further
details.

UseGateway=
When true, the gateway will be requested from the DHCP server and added to the routing
table with a metric of 1024, and a scope of link. When unset, the value specified with
UseRoutes= is used.

UseTimezone=
When true, the timezone received from the DHCP server will be set as timezone of the
local system. Defaults to false.

FallbackLeaseLifetimeSec=
Allows to set DHCPv4 lease lifetime when DHCPv4 server does not send the lease
lifetime. Takes one of "forever" or "infinity". The latter means that the address
never expires. Defaults to unset.

RequestBroadcast=
Request the server to use broadcast messages before the IP address has been
configured. This is necessary for devices that cannot receive RAW packets, or that
cannot receive packets at all before an IP address has been configured. On the other
hand, this must not be enabled on networks where broadcasts are filtered out.

MaxAttempts=
Specifies how many times the DHCPv4 client configuration should be attempted. Takes a
number or "infinity". Defaults to "infinity". Note that the time between retries is
increased exponentially, up to approximately one per minute, so the network will not
be overloaded even if this number is high. The default is suitable in most
circumstances.

ListenPort=
Set the port from which the DHCP client packets originate.

DenyList=
A whitespace-separated list of IPv4 addresses. DHCP offers from servers in the list
are rejected. Note that if AllowList= is configured then DenyList= is ignored.

AllowList=
A whitespace-separated list of IPv4 addresses. DHCP offers from servers in the list
are accepted.

SendRelease=
When true, the DHCPv4 client sends a DHCP release packet when it stops. Defaults to
true.

SendDecline=
A boolean. When "true", the DHCPv4 client receives the IP address from the DHCP
server. After a new IP is received, the DHCPv4 client performs IPv4 Duplicate Address
Detection. If duplicate use is detected, the DHCPv4 client rejects the IP by sending a
DHCPDECLINE packet and tries to obtain an IP address again. See RFC 5224[11]. Defaults
to "unset".

[DHCPV6] SECTION OPTIONS
The [DHCPv6] section configures the DHCPv6 client, if it is enabled with the DHCP= setting
described above, or invoked by the IPv6 Router Advertisement:

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

SendOption=
As in the [DHCPv4] section, however because DHCPv6 uses 16-bit fields to store option
numbers, the option number is an integer in the range 1...65536.

SendVendorOption=
Send an arbitrary vendor option in the DHCPv6 request. Takes an enterprise identifier,
DHCP option number, data type, and data separated with a colon ("enterprise
identifier:option:type:value"). Enterprise identifier is an unsigned integer in the
range 1...4294967294. The option number must be an integer in the range 1...254. Data
type takes one of "uint8", "uint16", "uint32", "ipv4address", "ipv6address", or
"string". Special characters in the data string may be escaped using C-style
escapes[18]. This setting can be specified multiple times. If an empty string is
specified, then all options specified earlier are cleared. Defaults to unset.

UserClass=
A DHCPv6 client can use User Class option to identify the type or category of user or
applications it represents. The information contained in this option is a string that
represents the user class of which the client is a member. Each class sets an
identifying string of information to be used by the DHCP service to classify clients.
Special characters in the data string may be escaped using C-style escapes[18]. This
setting can be specified multiple times. If an empty string is specified, then all
options specified earlier are cleared. Takes a whitespace-separated list of strings.
Note that currently NUL bytes are not allowed.

VendorClass=
A DHCPv6 client can use VendorClass option to identify the vendor that manufactured
the hardware on which the client is running. The information contained in the data
area of this option is contained in one or more opaque fields that identify details of
the hardware configuration. Takes a whitespace-separated list of strings.

PrefixDelegationHint=
Takes an IPv6 address with prefix length in the same format as the Address= in the
[Network] section. The DHCPv6 client will include a prefix hint in the DHCPv6
solicitation sent to the server. The prefix length must be in the range 1-128.
Defaults to unset.

UseAddress=
When true (the default), the IP addresses provided by the DHCPv6 server will be
assigned.

UseDNS=, UseNTP=, UseHostname=, UseDomains=
As in the [DHCPv4] section.

ForceDHCPv6PDOtherInformation=
Takes a boolean that enforces DHCPv6 stateful mode when the 'Other information' bit is
set in Router Advertisement messages. By default setting only the 'O' bit in Router
Advertisements makes DHCPv6 request network information in a stateless manner using a
two-message Information Request and Information Reply message exchange. RFC 7084[19],
requirement WPD-4, updates this behavior for a Customer Edge router so that stateful
DHCPv6 Prefix Delegation is also requested when only the 'O' bit is set in Router
Advertisements. This option enables such a CE behavior as it is impossible to
automatically distinguish the intention of the 'O' bit otherwise. By default this
option is set to false, enable it if no prefixes are delegated when the device should
be acting as a CE router.

WithoutRA=
Allows DHCPv6 client to start without router advertisements's managed or other address
configuration flag. Takes one of "solicit" or "information-request". Defaults to
unset.

RapidCommit=
Takes a boolean. The DHCPv6 client can obtain configuration parameters from a DHCPv6
server through a rapid two-message exchange (solicit and reply). When the rapid commit
option is enabled by both the DHCPv6 client and the DHCPv6 server, the two-message
exchange is used, rather than the default four-message exchange (solicit, advertise,
request, and reply). The two-message exchange provides faster client configuration and
is beneficial in environments in which networks are under a heavy load. See RFC
3315[20] for details. Defaults to true.

[DHCPV6PREFIXDELEGATION] SECTION OPTIONS
The [DHCPv6PrefixDelegation] section configures delegated prefixes assigned by DHCPv6
server. The settings in this section are used only when DHCPv6PrefixDelegation= setting is
enabled.

SubnetId=
Configure a specific subnet ID on the interface from a (previously) received prefix
delegation. You can either set "auto" (the default) or a specific subnet ID (as
defined in RFC 4291[21], section 2.5.4), in which case the allowed value is
hexadecimal, from 0 to 0x7fffffffffffffff inclusive.

Announce=
Takes a boolean. When enabled, and IPv6SendRA= in [Network] section is enabled, the
delegated prefixes are distributed through the IPv6 Router Advertisement. Defaults to
yes.

Assign=
Takes a boolean. Specifies whether to add an address from the delegated prefixes which
are received from the WAN interface by the DHCPv6 Prefix Delegation. When true (on LAN
interfce), the EUI-64 algorithm will be used by default to form an interface
identifier from the delegated prefixes. See also Token= setting below. Defaults to
yes.

Token=
Specifies an optional address generation mode for assigning an address in each
delegated prefix. Takes an IPv6 address. When set, the lower bits of the supplied
address is combined with the upper bits of each delegatad prefix received from the WAN
interface by the DHCPv6 Prefix Delegation to form a complete address. When Assign= is
disabled, this setting is ignored. When unset, the EUI-64 algorithm will be used to
form addresses. Defaults to unset.

ManageTemporaryAddress=
As in the [Address] section, but defaults to true.

RouteMetric=
The metric of the route to the delegated prefix subnet. Takes an unsigned integer in
the range 0...4294967295. When unset or set to 0, the kernel's default value is used.

[IPV6ACCEPTRA] SECTION OPTIONS
The [IPv6AcceptRA] section configures the IPv6 Router Advertisement (RA) client, if it is
enabled with the IPv6AcceptRA= setting described above:

UseDNS=
When true (the default), the DNS servers received in the Router Advertisement will be
used.

This corresponds to the nameserver option in resolv.conf(5).

UseDomains=
Takes a boolean, or the special value "route". When true, the domain name received via
IPv6 Router Advertisement (RA) will be used as DNS search domain over this link,
similar to the effect of the Domains= setting. If set to "route", the domain name
received via IPv6 RA will be used for routing DNS queries only, but not for searching,
similar to the effect of the Domains= setting when the argument is prefixed with "~".
Defaults to true on Ubuntu.

When set to true, this setting corresponds to the domain option in resolv.conf(5).

RouteTable=num
The table identifier for the routes received in the Router Advertisement (a number
between 1 and 4294967295, or 0 to unset). The table can be retrieved using ip route
show table num.

RouteMetric=
Set the routing metric for the routes received in the Router Advertisement. Takes an
unsigned integer in the range 0...4294967295. Defaults to 1024.

UseAutonomousPrefix=
When true (the default), the autonomous prefix received in the Router Advertisement
will be used and take precedence over any statically configured ones.

UseOnLinkPrefix=
When true (the default), the onlink prefix received in the Router Advertisement will
be used and takes precedence over any statically configured ones.

RouterDenyList=
A whitespace-separated list of IPv6 router addresses. Any information advertised by
the listed router is ignored.

RouterAllowList=
A whitespace-separated list of IPv6 router addresses. Only information advertised by
the listed router is accepted. Note that if RouterAllowList= is configured then
RouterDenyList= is ignored.

PrefixDenyList=
A whitespace-separated list of IPv6 prefixes. IPv6 prefixes supplied via router
advertisements in the list are ignored.

PrefixAllowList=
A whitespace-separated list of IPv6 prefixes. IPv6 prefixes supplied via router
advertisements in the list are allowed. Note that if PrefixAllowList= is configured
then PrefixDenyList= is ignored.

RouteDenyList=
A whitespace-separated list of IPv6 route prefixes. IPv6 route prefixes supplied via
router advertisements in the list are ignored.

RouteAllowList=
A whitespace-separated list of IPv6 route prefixes. IPv6 route prefixes supplied via
router advertisements in the list are allowed. Note that if RouteAllowList= is
configured then RouteDenyList= is ignored.

DHCPv6Client=
Takes a boolean, or the special value "always". When true or "always", the DHCPv6
client will be started when the RA has the managed or other information flag. If set
to "always", the DHCPv6 client will also be started in managed mode when neither
managed nor other information flag is set in the RA. Defaults to true.

[DHCPSERVER] SECTION OPTIONS
The [DHCPServer] section contains settings for the DHCP server, if enabled via the
DHCPServer= option described above:

ServerAddress=
Specifies server address for the DHCP server. Takes an IPv4 address with prefix
length, for example "192.168.0.1/24". This setting may be useful when the link on
which the DHCP server is running has multiple static addresses. When unset, one of
static addresses in the link will be automatically selected. Defaults to unset.

PoolOffset=, PoolSize=
Configures the pool of addresses to hand out. The pool is a contiguous sequence of IP
addresses in the subnet configured for the server address, which does not include the
subnet nor the broadcast address. PoolOffset= takes the offset of the pool from the
start of subnet, or zero to use the default value. PoolSize= takes the number of IP
addresses in the pool or zero to use the default value. By default, the pool starts at
the first address after the subnet address and takes up the rest of the subnet,
excluding the broadcast address. If the pool includes the server address (the
default), this is reserved and not handed out to clients.

DefaultLeaseTimeSec=, MaxLeaseTimeSec=
Control the default and maximum DHCP lease time to pass to clients. These settings
take time values in seconds or another common time unit, depending on the suffix. The
default lease time is used for clients that did not ask for a specific lease time. If
a client asks for a lease time longer than the maximum lease time, it is automatically
shortened to the specified time. The default lease time defaults to 1h, the maximum
lease time to 12h. Shorter lease times are beneficial if the configuration data in
DHCP leases changes frequently and clients shall learn the new settings with shorter
latencies. Longer lease times reduce the generated DHCP network traffic.

UplinkInterface=
Specifies name or index of uplink interface, or one of the special values ":none" and
":auto". When emitting DNS, NTP, or SIP servers are enabled but no servers are
specified, the servers configured in the uplink interface will be emitted. When
":auto", the link which has default gateway with higher priority will be automatically
selected. When ":none", no uplink interface will be selected. Defaults to ":auto".

EmitDNS=, DNS=
EmitDNS= takes a boolean. Configures whether the DHCP leases handed out to clients
shall contain DNS server information. Defaults to "yes". The DNS servers to pass to
clients may be configured with the DNS= option, which takes a list of IPv4 addresses.
If the EmitDNS= option is enabled but no servers configured, the servers are
automatically propagated from an "uplink" interface that has appropriate servers set.
The "uplink" interface is determined by the default route of the system with the
highest priority. Note that this information is acquired at the time the lease is
handed out, and does not take uplink interfaces into account that acquire DNS server
information at a later point. If no suitable uplink interface is found the DNS server
data from /etc/resolv.conf is used. Also, note that the leases are not refreshed if
the uplink network configuration changes. To ensure clients regularly acquire the most
current uplink DNS server information, it is thus advisable to shorten the DHCP lease
time via MaxLeaseTimeSec= described above.

EmitNTP=, NTP=, EmitSIP=, SIP=, EmitPOP3=, POP3=, EmitSMTP=, SMTP=, EmitLPR=, LPR=
Similar to the EmitDNS= and DNS= settings described above, these settings configure
whether and what server information for the indicate protocol shall be emitted as part
of the DHCP lease. The same syntax, propagation semantics and defaults apply as for
EmitDNS= and DNS=.

EmitRouter=
Similar to the EmitDNS= setting described above, this setting configures whether the
DHCP lease should contain the router option. The same syntax, propagation semantics
and defaults apply as for EmitDNS=.

EmitTimezone=, Timezone=
Takes a boolean. Configures whether the DHCP leases handed out to clients shall
contain timezone information. Defaults to "yes". The Timezone= setting takes a
timezone string (such as "Europe/Berlin" or "UTC") to pass to clients. If no explicit
timezone is set, the system timezone of the local host is propagated, as determined by
the /etc/localtime symlink.

SendOption=
Send a raw option with value via DHCPv4 server. Takes a DHCP option number, data type
and data ("option:type:value"). The option number is an integer in the range 1...254.
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[18]. This setting can be specified multiple times. If an empty string is
specified, then all options specified earlier are cleared. Defaults to unset.

SendVendorOption=
Send a vendor option with value via DHCPv4 server. Takes a DHCP option number, data
type and data ("option:type:value"). The option number is an integer in the range
1...254. The type takes one of "uint8", "uint16", "uint32", "ipv4address", or
"string". Special characters in the data string may be escaped using C-style
escapes[18]. This setting can be specified multiple times. If an empty string is
specified, then all options specified earlier are cleared. Defaults to unset.

BindToInterface=
Takes a boolean value. When "yes", DHCP server socket will be bound to its network
interface and all socket communication will be restricted to this interface. Defaults
to "yes", except if RelayTarget= is used (see below), in which case it defaults
defaults to "no".

RelayTarget=
Takes an IPv4 address, which must be in the format described in inet_pton(3). Turns
this DHCP server into a DHCP relay agent. See RFC 1542[22]. The address is the address
of DHCP server or another relay agent to forward DHCP messages to and from.

RelayAgentCircuitId=
Specifies value for Agent Circuit ID suboption of Relay Agent Information option.
Takes a string, which must be in the format "string:value", where "value" should be
replaced with the value of the suboption. Defaults to unset (means no Agent Circuit ID
suboption is generated). Ignored if RelayTarget= is not specified.

RelayAgentRemoteId=
Specifies value for Agent Remote ID suboption of Relay Agent Information option. Takes
a string, which must be in the format "string:value", where "value" should be replaced
with the value of the suboption. Defaults to unset (means no Agent Remote ID suboption
is generated). Ignored if RelayTarget= is not specified.

[DHCPSERVERSTATICLEASE] SECTION OPTIONS
The "[DHCPServerStaticLease]" section configures a static DHCP lease to assign a fixed
IPv4 address to a specific device based on its MAC address. This section can be specified
multiple times.

MACAddress=
The hardware address of a device to match. This key is mandatory.

Address=
The IPv4 address that should be assigned to the device that was matched with
MACAddress=. This key is mandatory.

[IPV6SENDRA] SECTION OPTIONS
The [IPv6SendRA] section contains settings for sending IPv6 Router Advertisements and
whether to act as a router, if enabled via the IPv6SendRA= option described above. IPv6
network prefixes or routes are defined with one or more [IPv6Prefix] or [IPv6RoutePrefix]
sections.

Managed=, OtherInformation=
Takes a boolean. Controls whether a DHCPv6 server is used to acquire IPv6 addresses on
the network link when Managed= is set to "true" or if only additional network
information can be obtained via DHCPv6 for the network link when OtherInformation= is
set to "true". Both settings default to "false", which means that a DHCPv6 server is
not being used.

RouterLifetimeSec=
Takes a timespan. Configures the IPv6 router lifetime in seconds. When set to 0, the
host is not acting as a router. Defaults to 30 minutes.

RouterPreference=
Configures IPv6 router preference if RouterLifetimeSec= is non-zero. Valid values are
"high", "medium" and "low", with "normal" and "default" added as synonyms for "medium"
just to make configuration easier. See RFC 4191[15] for details. Defaults to "medium".

EmitDNS=, DNS=
DNS= specifies a list of recursive DNS server IPv6 addresses that are distributed via
Router Advertisement messages when EmitDNS= is true. DNS= also takes special value
"_link_local"; in that case the IPv6 link local address is distributed. If DNS= is
empty, DNS servers are read from the [Network] section. If the [Network] section does
not contain any DNS servers either, DNS servers from the uplink with the highest
priority default route are used. When EmitDNS= is false, no DNS server information is
sent in Router Advertisement messages. EmitDNS= defaults to true.

EmitDomains=, Domains=
A list of DNS search domains distributed via Router Advertisement messages when
EmitDomains= is true. If Domains= is empty, DNS search domains are read from the
[Network] section. If the [Network] section does not contain any DNS search domains
either, DNS search domains from the uplink with the highest priority default route are
used. When EmitDomains= is false, no DNS search domain information is sent in Router
Advertisement messages. EmitDomains= defaults to true.

DNSLifetimeSec=
Lifetime in seconds for the DNS server addresses listed in DNS= and search domains
listed in Domains=.

[IPV6PREFIX] SECTION OPTIONS
One or more [IPv6Prefix] sections contain the IPv6 prefixes that are announced via Router
Advertisements. See RFC 4861[23] for further details.

AddressAutoconfiguration=, OnLink=
Takes a boolean to specify whether IPv6 addresses can be autoconfigured with this
prefix and whether the prefix can be used for onlink determination. Both settings
default to "true" in order to ease configuration.

Prefix=
The IPv6 prefix that is to be distributed to hosts. Similarly to configuring static
IPv6 addresses, the setting is configured as an IPv6 prefix and its prefix length,
separated by a "/" character. Use multiple [IPv6Prefix] sections to configure multiple
IPv6 prefixes since prefix lifetimes, address autoconfiguration and onlink status may
differ from one prefix to another.

PreferredLifetimeSec=, ValidLifetimeSec=
Preferred and valid lifetimes for the prefix measured in seconds.
PreferredLifetimeSec= defaults to 604800 seconds (one week) and ValidLifetimeSec=
defaults to 2592000 seconds (30 days).

Assign=
Takes a boolean. When true, adds an address from the prefix. Default to false.

RouteMetric=
The metric of the prefix route. Takes an unsigned integer in the range 0...4294967295.
When unset or set to 0, the kernel's default value is used. This setting is ignored
when Assign= is false.

[IPV6ROUTEPREFIX] SECTION OPTIONS
One or more [IPv6RoutePrefix] sections contain the IPv6 prefix routes that are announced
via Router Advertisements. See RFC 4191[15] for further details.

Route=
The IPv6 route that is to be distributed to hosts. Similarly to configuring static
IPv6 routes, the setting is configured as an IPv6 prefix routes and its prefix route
length, separated by a "/" character. Use multiple [IPv6PrefixRoutes] sections to
configure multiple IPv6 prefix routes.

LifetimeSec=
Lifetime for the route prefix measured in seconds. LifetimeSec= defaults to 604800
seconds (one week).

[BRIDGE] SECTION OPTIONS
The [Bridge] section accepts the following keys:

UnicastFlood=
Takes a boolean. Controls whether the bridge should flood traffic for which an FDB
entry is missing and the destination is unknown through this port. When unset, the
kernel's default will be used.

MulticastFlood=
Takes a boolean. Controls whether the bridge should flood traffic for which an MDB
entry is missing and the destination is unknown through this port. When unset, the
kernel's default will be used.

MulticastToUnicast=
Takes a boolean. Multicast to unicast works on top of the multicast snooping feature
of the bridge. Which means unicast copies are only delivered to hosts which are
interested in it. When unset, the kernel's default will be used.

NeighborSuppression=
Takes a boolean. Configures whether ARP and ND neighbor suppression is enabled for
this port. When unset, the kernel's default will be used.

Learning=
Takes a boolean. Configures whether MAC address learning is enabled for this port.
When unset, the kernel's default will be used.

HairPin=
Takes a boolean. Configures whether traffic may be sent back out of the port on which
it was received. When this flag is false, then the bridge will not forward traffic
back out of the receiving port. When unset, the kernel's default will be used.

UseBPDU=
Takes a boolean. Configures whether STP Bridge Protocol Data Units will be processed
by the bridge port. When unset, the kernel's default will be used.

FastLeave=
Takes a boolean. This flag allows the bridge to immediately stop multicast traffic on
a port that receives an IGMP Leave message. It is only used with IGMP snooping if
enabled on the bridge. When unset, the kernel's default will be used.

AllowPortToBeRoot=
Takes a boolean. Configures whether a given port is allowed to become a root port.
Only used when STP is enabled on the bridge. When unset, the kernel's default will be
used.

ProxyARP=
Takes a boolean. Configures whether proxy ARP to be enabled on this port. When unset,
the kernel's default will be used.

ProxyARPWiFi=
Takes a boolean. Configures whether proxy ARP to be enabled on this port which meets
extended requirements by IEEE 802.11 and Hotspot 2.0 specifications. When unset, the
kernel's default will be used.

MulticastRouter=
Configures this port for having multicast routers attached. A port with a multicast
router will receive all multicast traffic. Takes one of "no" to disable multicast
routers on this port, "query" to let the system detect the presence of routers,
"permanent" to permanently enable multicast traffic forwarding on this port, or
"temporary" to enable multicast routers temporarily on this port, not depending on
incoming queries. When unset, the kernel's default will be used.

Cost=
Sets the "cost" of sending packets of this interface. Each port in a bridge may have a
different speed and the cost is used to decide which link to use. Faster interfaces
should have lower costs. It is an integer value between 1 and 65535.

Priority=
Sets the "priority" of sending packets on this interface. Each port in a bridge may
have a different priority which is used to decide which link to use. Lower value means
higher priority. It is an integer value between 0 to 63. Networkd does not set any
default, meaning the kernel default value of 32 is used.

[BRIDGEFDB] SECTION OPTIONS
The [BridgeFDB] section manages the forwarding database table of a port and accepts the
following keys. Specify several [BridgeFDB] sections to configure several static MAC table
entries.

MACAddress=
As in the [Network] section. This key is mandatory.

Destination=
Takes an IP address of the destination VXLAN tunnel endpoint.

VLANId=
The VLAN ID for the new static MAC table entry. If omitted, no VLAN ID information is
appended to the new static MAC table entry.

VNI=
The VXLAN Network Identifier (or VXLAN Segment ID) to use to connect to the remote
VXLAN tunnel endpoint. Takes a number in the range 1...16777215. Defaults to unset.

AssociatedWith=
Specifies where the address is associated with. Takes one of "use", "self", "master"
or "router". "use" means the address is in use. User space can use this option to
indicate to the kernel that the fdb entry is in use. "self" means the address is
associated with the port drivers fdb. Usually hardware. "master" means the address is
associated with master devices fdb. "router" means the destination address is
associated with a router. Note that it's valid if the referenced device is a VXLAN
type device and has route shortcircuit enabled. Defaults to "self".

OutgoingInterface=
Specifies the name or index of the outgoing interface for the VXLAN device driver to
reach the remote VXLAN tunnel endpoint. Defaults to unset.

[BRIDGEMDB] SECTION OPTIONS
The [BridgeMDB] section manages the multicast membership entries forwarding database table
of a port and accepts the following keys. Specify several [BridgeMDB] sections to
configure several permanent multicast membership entries.

MulticastGroupAddress=
Specifies the IPv4 or IPv6 multicast group address to add. This setting is mandatory.

VLANId=
The VLAN ID for the new entry. Valid ranges are 0 (no VLAN) to 4094. Optional,
defaults to 0.

[LLDP] SECTION OPTIONS
The [LLDP] section manages the Link Layer Discovery Protocol (LLDP) and accepts the
following keys:

MUDURL=
When configured, the specified Manufacturer Usage Descriptions (MUD) URL will be sent
in LLDP packets. The syntax and semantics are the same as for MUDURL= in the [DHCPv4]
section described above.

The MUD URLs received via LLDP packets are saved and can be read using the
sd_lldp_neighbor_get_mud_url() function.

[CAN] SECTION OPTIONS
The [CAN] section manages the Controller Area Network (CAN bus) and accepts the following
keys:

BitRate=
The bitrate of CAN device in bits per second. The usual SI prefixes (K, M) with the
base of 1000 can be used here. Takes a number in the range 1...4294967295.

SamplePoint=
Optional sample point in percent with one decimal (e.g. "75%", "87.5%") or permille
(e.g. "875<permille>").

DataBitRate=, DataSamplePoint=
The bitrate and sample point for the data phase, if CAN-FD is used. These settings are
analogous to the BitRate= and SamplePoint= keys.

FDMode=
Takes a boolean. When "yes", CAN-FD mode is enabled for the interface. Note, that a
bitrate and optional sample point should also be set for the CAN-FD data phase using
the DataBitRate= and DataSamplePoint= keys.

FDNonISO=
Takes a boolean. When "yes", non-ISO CAN-FD mode is enabled for the interface. When
unset, the kernel's default will be used.

RestartSec=
Automatic restart delay time. If set to a non-zero value, a restart of the CAN
controller will be triggered automatically in case of a bus-off condition after the
specified delay time. Subsecond delays can be specified using decimals (e.g. "0.1s")
or a "ms" or "us" postfix. Using "infinity" or "0" will turn the automatic restart
off. By default automatic restart is disabled.

Termination=
Takes a boolean. When "yes", the termination resistor will be selected for the bias
network. When unset, the kernel's default will be used.

TripleSampling=
Takes a boolean. When "yes", three samples (instead of one) are used to determine the
value of a received bit by majority rule. When unset, the kernel's default will be
used.

BusErrorReporting=
Takes a boolean. When "yes", reporting of CAN bus errors is activated (those include
single bit, frame format, and bit stuffing errors, unable to send dominant bit, unable
to send recessive bit, bus overload, active error announcement, error occurred on
transmission). When unset, the kernel's default will be used. Note: in case of a CAN
bus with a single CAN device, sending a CAN frame may result in a huge number of CAN
bus errors.

ListenOnly=
Takes a boolean. When "yes", listen-only mode is enabled. When the interface is in
listen-only mode, the interface neither transmit CAN frames nor send ACK bit.
Listen-only mode is important to debug CAN networks without interfering with the
communication or acknowledge the CAN frame. When unset, the kernel's default will be
used.

[QDISC] SECTION OPTIONS
The [QDisc] section manages the traffic control queueing discipline (qdisc).

Parent=
Specifies the parent Queueing Discipline (qdisc). Takes one of "clsact" or "ingress".
This is mandatory.

Handle=
Configures the major number of unique identifier of the qdisc, known as the handle.
Takes a hexadecimal number in the range 0x1-0xffff. Defaults to unset.

[NETWORKEMULATOR] SECTION OPTIONS
The [NetworkEmulator] section manages the queueing discipline (qdisc) of the network
emulator. It can be used to configure the kernel packet scheduler and simulate packet
delay and loss for UDP or TCP applications, or limit the bandwidth usage of a particular
service to simulate internet connections.

Parent=
Configures the parent Queueing Discipline (qdisc). Takes one of "root", "clsact",
"ingress" or a class identifier. The class identifier is specified as the major and
minor numbers in hexadecimal in the range 0x1-Oxffff separated with a colon
("major:minor"). Defaults to "root".

Handle=
Configures the major number of unique identifier of the qdisc, known as the handle.
Takes a hexadecimal number in the range 0x1-0xffff. Defaults to unset.

DelaySec=
Specifies the fixed amount of delay to be added to all packets going out of the
interface. Defaults to unset.

DelayJitterSec=
Specifies the chosen delay to be added to the packets outgoing to the network
interface. Defaults to unset.

PacketLimit=
Specifies the maximum number of packets the qdisc may hold queued at a time. An
unsigned integer in the range 0-4294967294. Defaults to 1000.

LossRate=
Specifies an independent loss probability to be added to the packets outgoing from the
network interface. Takes a percentage value, suffixed with "%". Defaults to unset.

DuplicateRate=
Specifies that the chosen percent of packets is duplicated before queuing them. Takes
a percentage value, suffixed with "%". Defaults to unset.

[TOKENBUCKETFILTER] SECTION OPTIONS
The [TokenBucketFilter] section manages the queueing discipline (qdisc) of token bucket
filter (tbf).

Handle=
Configures the major number of unique identifier of the qdisc, known as the handle.
Takes a hexadecimal number in the range 0x1-0xffff. Defaults to unset.

LatencySec=
Specifies the latency parameter, which specifies the maximum amount of time a packet
can sit in the Token Bucket Filter (TBF). Defaults to unset.

LimitBytes=
Takes the number of bytes that can be queued waiting for tokens to become available.
When the size is suffixed with K, M, or G, it is parsed as Kilobytes, Megabytes, or
Gigabytes, respectively, to the base of 1024. Defaults to unset.

BurstBytes=
Specifies the size of the bucket. This is the maximum amount of bytes that tokens can
be available for instantaneous transfer. When the size is suffixed with K, M, or G, it
is parsed as Kilobytes, Megabytes, or Gigabytes, respectively, to the base of 1024.
Defaults to unset.

Rate=
Specifies the device specific bandwidth. When suffixed with K, M, or G, the specified
bandwidth is parsed as Kilobits, Megabits, or Gigabits, respectively, to the base of
1000. Defaults to unset.

MPUBytes=
The Minimum Packet Unit (MPU) determines the minimal token usage (specified in bytes)
for a packet. When suffixed with K, M, or G, the specified size is parsed as
Kilobytes, Megabytes, or Gigabytes, respectively, to the base of 1024. Defaults to
zero.

PeakRate=
Takes the maximum depletion rate of the bucket. When suffixed with K, M, or G, the
specified size is parsed as Kilobits, Megabits, or Gigabits, respectively, to the base
of 1000. Defaults to unset.

MTUBytes=
Specifies the size of the peakrate bucket. When suffixed with K, M, or G, the
specified size is parsed as Kilobytes, Megabytes, or Gigabytes, respectively, to the
base of 1024. Defaults to unset.

[PIE] SECTION OPTIONS
The [PIE] section manages the queueing discipline (qdisc) of Proportional Integral
controller-Enhanced (PIE).

Handle=
Configures the major number of unique identifier of the qdisc, known as the handle.
Takes a hexadecimal number in the range 0x1-0xffff. Defaults to unset.

PacketLimit=
Specifies the hard limit on the queue size in number of packets. When this limit is
reached, incoming packets are dropped. An unsigned integer in the range
1...4294967294. Defaults to unset and kernel's default is used.

[FLOWQUEUEPIE] SECTION OPTIONS
The "[FlowQueuePIE]" section manages the queueing discipline (qdisc) of Flow Queue
Proportional Integral controller-Enhanced (fq_pie).

Handle=
Configures the major number of unique identifier of the qdisc, known as the handle.
Takes a hexadecimal number in the range 0x1-0xffff. Defaults to unset.

PacketLimit=
Specifies the hard limit on the queue size in number of packets. When this limit is
reached, incoming packets are dropped. An unsigned integer ranges 1 to 4294967294.
Defaults to unset and kernel's default is used.

[STOCHASTICFAIRBLUE] SECTION OPTIONS
The [StochasticFairBlue] section manages the queueing discipline (qdisc) of stochastic
fair blue (sfb).

Handle=
Configures the major number of unique identifier of the qdisc, known as the handle.
Takes a hexadecimal number in the range 0x1-0xffff. Defaults to unset.

PacketLimit=
Specifies the hard limit on the queue size in number of packets. When this limit is
reached, incoming packets are dropped. An unsigned integer in the range 0-4294967294.
Defaults to unset and kernel's default is used.

[STOCHASTICFAIRNESSQUEUEING] SECTION OPTIONS
The [StochasticFairnessQueueing] section manages the queueing discipline (qdisc) of
stochastic fairness queueing (sfq).

Handle=
Configures the major number of unique identifier of the qdisc, known as the handle.
Takes a hexadecimal number in the range 0x1-0xffff. Defaults to unset.

PerturbPeriodSec=
Specifies the interval in seconds for queue algorithm perturbation. Defaults to unset.

[BFIFO] SECTION OPTIONS
The [BFIFO] section manages the queueing discipline (qdisc) of Byte limited Packet First
In First Out (bfifo).

Handle=
Configures the major number of unique identifier of the qdisc, known as the handle.
Takes a hexadecimal number in the range 0x1-0xffff. Defaults to unset.

LimitBytes=
Specifies the hard limit in bytes on the FIFO buffer size. The size limit prevents
overflow in case the kernel is unable to dequeue packets as quickly as it receives
them. When this limit is reached, incoming packets are dropped. When suffixed with K,
M, or G, the specified size is parsed as Kilobytes, Megabytes, or Gigabytes,
respectively, to the base of 1024. Defaults to unset and kernel default is used.

[PFIFO] SECTION OPTIONS
The [PFIFO] section manages the queueing discipline (qdisc) of Packet First In First Out
(pfifo).

Handle=
Configures the major number of unique identifier of the qdisc, known as the handle.
Takes a hexadecimal number in the range 0x1-0xffff. Defaults to unset.

PacketLimit=
Specifies the hard limit on the number of packets in the FIFO queue. The size limit
prevents overflow in case the kernel is unable to dequeue packets as quickly as it
receives them. When this limit is reached, incoming packets are dropped. An unsigned
integer in the range 0-4294967294. Defaults to unset and kernel's default is used.

[PFIFOHEADDROP] SECTION OPTIONS
The [PFIFOHeadDrop] section manages the queueing discipline (qdisc) of Packet First In
First Out Head Drop (pfifo_head_drop).

Handle=
Configures the major number of unique identifier of the qdisc, known as the handle.
Takes a hexadecimal number in the range 0x1-0xffff. Defaults to unset.

PacketLimit=
As in [PFIFO] section.

[PFIFOFAST] SECTION OPTIONS
The [PFIFOFast] section manages the queueing discipline (qdisc) of Packet First In First
Out Fast (pfifo_fast).

Handle=
Configures the major number of unique identifier of the qdisc, known as the handle.
Takes a hexadecimal number in the range 0x1-0xffff. Defaults to unset.

[CAKE] SECTION OPTIONS
The [CAKE] section manages the queueing discipline (qdisc) of Common Applications Kept
Enhanced (CAKE).

Handle=
Configures the major number of unique identifier of the qdisc, known as the handle.
Takes a hexadecimal number in the range 0x1-0xffff. Defaults to unset.

OverheadBytes=
Specifies that bytes to be addeded to the size of each packet. Bytes may be negative.
Takes an integer in the range from -64 to 256. Defaults to unset and kernel's default
is used.

Bandwidth=
Specifies the shaper bandwidth. When suffixed with K, M, or G, the specified size is
parsed as Kilobits, Megabits, or Gigabits, respectively, to the base of 1000. Defaults
to unset and kernel's default is used.

[CONTROLLEDDELAY] SECTION OPTIONS
The [ControlledDelay] section manages the queueing discipline (qdisc) of controlled delay
(CoDel).

Handle=
Configures the major number of unique identifier of the qdisc, known as the handle.
Takes a hexadecimal number in the range 0x1-0xffff. Defaults to unset.

TargetSec=
Takes a timespan. Specifies the acceptable minimum standing/persistent queue delay.
Defaults to unset and kernel's default is used.

IntervalSec=
Takes a timespan. This is used to ensure that the measured minimum delay does not
become too stale. Defaults to unset and kernel's default is used.

ECN=
Takes a boolean. This can be used to mark packets instead of dropping them. Defaults
to unset and kernel's default is used.

CEThresholdSec=
Takes a timespan. This sets a threshold above which all packets are marked with ECN
Congestion Experienced (CE). Defaults to unset and kernel's default is used.

[DEFICITROUNDROBINSCHEDULER] SECTION OPTIONS
The [DeficitRoundRobinScheduler] section manages the queueing discipline (qdisc) of
Deficit Round Robin Scheduler (DRR).

Handle=
Configures the major number of unique identifier of the qdisc, known as the handle.
Takes a hexadecimal number in the range 0x1-0xffff. Defaults to unset.

[DEFICITROUNDROBINSCHEDULERCLASS] SECTION OPTIONS
The [DeficitRoundRobinSchedulerClass] section manages the traffic control class of Deficit
Round Robin Scheduler (DRR).

Parent=
Configures the parent Queueing Discipline (qdisc). Takes one of "root", or a qdisc
identifier. The qdisc identifier is specified as the major and minor numbers in
hexadecimal in the range 0x1-Oxffff separated with a colon ("major:minor"). Defaults
to "root".

ClassId=
Configures the unique identifier of the class. It is specified as the major and minor
numbers in hexadecimal in the range 0x1-Oxffff separated with a colon ("major:minor").
Defaults to unset.

QuantumBytes=
Specifies the amount of bytes a flow is allowed to dequeue before the scheduler moves
to the next class. When suffixed with K, M, or G, the specified size is parsed as
Kilobytes, Megabytes, or Gigabytes, respectively, to the base of 1024. Defaults to the
MTU of the interface.

[ENHANCEDTRANSMISSIONSELECTION] SECTION OPTIONS
The [EnhancedTransmissionSelection] section manages the queueing discipline (qdisc) of
Enhanced Transmission Selection (ETS).

Handle=
Configures the major number of unique identifier of the qdisc, known as the handle.
Takes a hexadecimal number in the range 0x1-0xffff. Defaults to unset.

Bands=
Specifies the number of bands. An unsigned integer in the range 1-16. This value has
to be at least large enough to cover the strict bands specified through the
StrictBands= and bandwidth-sharing bands specified in QuantumBytes=.

StrictBands=
Specifies the number of bands that should be created in strict mode. An unsigned
integer in the range 1-16.

QuantumBytes=
Specifies the white-space separated list of quantum used in band-sharing bands. When
suffixed with K, M, or G, the specified size is parsed as Kilobytes, Megabytes, or
Gigabytes, respectively, to the base of 1024. This setting can be specified multiple
times. If an empty string is assigned, then the all previous assignments are cleared.

PriorityMap=
The priority map maps the priority of a packet to a band. The argument is a whitespace
separated list of numbers. The first number indicates which band the packets with
priority 0 should be put to, the second is for priority 1, and so on. There can be up
to 16 numbers in the list. If there are fewer, the default band that traffic with one
of the unmentioned priorities goes to is the last one. Each band number must be in the
range 0...255. This setting can be specified multiple times. If an empty string is
assigned, then the all previous assignments are cleared.

[GENERICRANDOMEARLYDETECTION] SECTION OPTIONS
The [GenericRandomEarlyDetection] section manages the queueing discipline (qdisc) of
Generic Random Early Detection (GRED).

Handle=
Configures the major number of unique identifier of the qdisc, known as the handle.
Takes a hexadecimal number in the range 0x1-0xffff. Defaults to unset.

VirtualQueues=
Specifies the number of virtual queues. Takes an integer in the range 1...16. Defaults
to unset and kernel's default is used.

DefaultVirtualQueue=
Specifies the number of default virtual queue. This must be less than VirtualQueue=.
Defaults to unset and kernel's default is used.

GenericRIO=
Takes a boolean. It turns on the RIO-like buffering scheme. Defaults to unset and
kernel's default is used.

[FAIRQUEUEINGCONTROLLEDDELAY] SECTION OPTIONS
The [FairQueueingControlledDelay] section manages the queueing discipline (qdisc) of fair
queuing controlled delay (FQ-CoDel).

Handle=
Configures the major number of unique identifier of the qdisc, known as the handle.
Takes a hexadecimal number in the range 0x1-0xffff. Defaults to unset.

PacketLimit=
Specifies the hard limit on the real queue size. When this limit is reached, incoming
packets are dropped. Defaults to unset and kernel's default is used.

MemoryLimitBytes=
Specifies the limit on the total number of bytes that can be queued in this FQ-CoDel
instance. When suffixed with K, M, or G, the specified size is parsed as Kilobytes,
Megabytes, or Gigabytes, respectively, to the base of 1024. Defaults to unset and
kernel's default is used.

Flows=
Specifies the number of flows into which the incoming packets are classified. Defaults
to unset and kernel's default is used.

TargetSec=
Takes a timespan. Specifies the acceptable minimum standing/persistent queue delay.
Defaults to unset and kernel's default is used.

IntervalSec=
Takes a timespan. This is used to ensure that the measured minimum delay does not
become too stale. Defaults to unset and kernel's default is used.

QuantumBytes=
Specifies the number of bytes used as the "deficit" in the fair queuing algorithm
timespan. When suffixed with K, M, or G, the specified size is parsed as Kilobytes,
Megabytes, or Gigabytes, respectively, to the base of 1024. Defaults to unset and
kernel's default is used.

ECN=
Takes a boolean. This can be used to mark packets instead of dropping them. Defaults
to unset and kernel's default is used.

CEThresholdSec=
Takes a timespan. This sets a threshold above which all packets are marked with ECN
Congestion Experienced (CE). Defaults to unset and kernel's default is used.

[FAIRQUEUEING] SECTION OPTIONS
The [FairQueueing] section manages the queueing discipline (qdisc) of fair queue traffic
policing (FQ).

Handle=
Configures the major number of unique identifier of the qdisc, known as the handle.
Takes a hexadecimal number in the range 0x1-0xffff. Defaults to unset.

PacketLimit=
Specifies the hard limit on the real queue size. When this limit is reached, incoming
packets are dropped. Defaults to unset and kernel's default is used.

FlowLimit=
Specifies the hard limit on the maximum number of packets queued per flow. Defaults to
unset and kernel's default is used.

QuantumBytes=
Specifies the credit per dequeue RR round, i.e. the amount of bytes a flow is allowed
to dequeue at once. When suffixed with K, M, or G, the specified size is parsed as
Kilobytes, Megabytes, or Gigabytes, respectively, to the base of 1024. Defaults to
unset and kernel's default is used.

InitialQuantumBytes=
Specifies the initial sending rate credit, i.e. the amount of bytes a new flow is
allowed to dequeue initially. When suffixed with K, M, or G, the specified size is
parsed as Kilobytes, Megabytes, or Gigabytes, respectively, to the base of 1024.
Defaults to unset and kernel's default is used.

MaximumRate=
Specifies the maximum sending rate of a flow. When suffixed with K, M, or G, the
specified size is parsed as Kilobits, Megabits, or Gigabits, respectively, to the base
of 1000. Defaults to unset and kernel's default is used.

Buckets=
Specifies the size of the hash table used for flow lookups. Defaults to unset and
kernel's default is used.

OrphanMask=
Takes an unsigned integer. For packets not owned by a socket, fq is able to mask a
part of hash and reduce number of buckets associated with the traffic. Defaults to
unset and kernel's default is used.

Pacing=
Takes a boolean, and enables or disables flow pacing. Defaults to unset and kernel's
default is used.

CEThresholdSec=
Takes a timespan. This sets a threshold above which all packets are marked with ECN
Congestion Experienced (CE). Defaults to unset and kernel's default is used.

[TRIVIALLINKEQUALIZER] SECTION OPTIONS
The [TrivialLinkEqualizer] section manages the queueing discipline (qdisc) of trivial link
equalizer (teql).

Handle=
Configures the major number of unique identifier of the qdisc, known as the handle.
Takes a hexadecimal number in the range 0x1-0xffff. Defaults to unset.

Id=
Specifies the interface ID "N" of teql. Defaults to "0". Note that when teql is used,
currently, the module sch_teql with max_equalizers=N+1 option must be loaded before
systemd-networkd is started.

[HIERARCHYTOKENBUCKET] SECTION OPTIONS
The [HierarchyTokenBucket] section manages the queueing discipline (qdisc) of hierarchy
token bucket (htb).

Handle=
Configures the major number of unique identifier of the qdisc, known as the handle.
Takes a hexadecimal number in the range 0x1-0xffff. Defaults to unset.

DefaultClass=
Takes the minor id in hexadecimal of the default class. Unclassified traffic gets sent
to the class. Defaults to unset.

RateToQuantum=
Takes an unsigned integer. The DRR quantums are calculated by dividing the value
configured in Rate= by RateToQuantum=.

[HIERARCHYTOKENBUCKETCLASS] SECTION OPTIONS
The [HierarchyTokenBucketClass] section manages the traffic control class of hierarchy
token bucket (htb).

Priority=
Specifies the priority of the class. In the round-robin process, classes with the
lowest priority field are tried for packets first.

QuantumBytes=
Specifies how many bytes to serve from leaf at once. When suffixed with K, M, or G,
the specified size is parsed as Kilobytes, Megabytes, or Gigabytes, respectively, to
the base of 1024.

MTUBytes=
Specifies the maximum packet size we create. When suffixed with K, M, or G, the
specified size is parsed as Kilobytes, Megabytes, or Gigabytes, respectively, to the
base of 1024.

OverheadBytes=
Takes an unsigned integer which specifies per-packet size overhead used in rate
computations. When suffixed with K, M, or G, the specified size is parsed as
Kilobytes, Megabytes, or Gigabytes, respectively, to the base of 1024.

Rate=
Specifies the maximum rate this class and all its children are guaranteed. When
suffixed with K, M, or G, the specified size is parsed as Kilobits, Megabits, or
Gigabits, respectively, to the base of 1000. This setting is mandatory.

CeilRate=
Specifies the maximum rate at which a class can send, if its parent has bandwidth to
spare. When suffixed with K, M, or G, the specified size is parsed as Kilobits,
Megabits, or Gigabits, respectively, to the base of 1000. When unset, the value
specified with Rate= is used.

BufferBytes=
Specifies the maximum bytes burst which can be accumulated during idle period. When
suffixed with K, M, or G, the specified size is parsed as Kilobytes, Megabytes, or
Gigabytes, respectively, to the base of 1024.

CeilBufferBytes=
Specifies the maximum bytes burst for ceil which can be accumulated during idle
period. When suffixed with K, M, or G, the specified size is parsed as Kilobytes,
Megabytes, or Gigabytes, respectively, to the base of 1024.

[HEAVYHITTERFILTER] SECTION OPTIONS
The [HeavyHitterFilter] section manages the queueing discipline (qdisc) of Heavy Hitter
Filter (hhf).

Handle=
Configures the major number of unique identifier of the qdisc, known as the handle.
Takes a hexadecimal number in the range 0x1-0xffff. Defaults to unset.

[QUICKFAIRQUEUEING] SECTION OPTIONS
The [QuickFairQueueing] section manages the queueing discipline (qdisc) of Quick Fair
Queueing (QFQ).

Handle=
Configures the major number of unique identifier of the qdisc, known as the handle.
Takes a hexadecimal number in the range 0x1-0xffff. Defaults to unset.

[QUICKFAIRQUEUEINGCLASS] SECTION OPTIONS
The [QuickFairQueueingClass] section manages the traffic control class of Quick Fair
Queueing (qfq).

Weight=
Specifies the weight of the class. Takes an integer in the range 1...1023. Defaults to
unset in which case the kernel default is used.

MaxPacketBytes=
Specifies the maximum packet size in bytes for the class. When suffixed with K, M, or
G, the specified size is parsed as Kilobytes, Megabytes, or Gigabytes, respectively,
to the base of 1024. When unset, the kernel default is used.

[BRIDGEVLAN] SECTION OPTIONS
The [BridgeVLAN] section manages the VLAN ID configuration of a bridge port and accepts
the following keys. Specify several [BridgeVLAN] sections to configure several VLAN
entries. The VLANFiltering= option has to be enabled, see the [Bridge] section in
systemd.netdev(5).

VLAN=
The VLAN ID allowed on the port. This can be either a single ID or a range M-N. VLAN
IDs are valid from 1 to 4094.

EgressUntagged=
The VLAN ID specified here will be used to untag frames on egress. Configuring
EgressUntagged= implicates the use of VLAN= above and will enable the VLAN ID for
ingress as well. This can be either a single ID or a range M-N.

PVID=
The Port VLAN ID specified here is assigned to all untagged frames at ingress. PVID=
can be used only once. Configuring PVID= implicates the use of VLAN= above and will
enable the VLAN ID for ingress as well.

EXAMPLES
Example 1. Static network configuration

# /etc/systemd/network/50-static.network
[Match]
Name=enp2s0

[Network]
Address=192.168.0.15/24
Gateway=192.168.0.1

This brings interface "enp2s0" up with a static address. The specified gateway will be
used for a default route.

Example 2. DHCP on ethernet links

# /etc/systemd/network/80-dhcp.network
[Match]
Name=en*

[Network]
DHCP=yes

This will enable DHCPv4 and DHCPv6 on all interfaces with names starting with "en" (i.e.
ethernet interfaces).

Example 3. IPv6 Prefix Delegation

# /etc/systemd/network/55-ipv6-pd-upstream.network
[Match]
Name=enp1s0

[Network]
DHCP=ipv6

# /etc/systemd/network/56-ipv6-pd-downstream.network
[Match]
Name=enp2s0

[Network]
IPv6SendRA=yes
DHCPv6PrefixDelegation=yes

This will enable DHCPv6-PD on the interface enp1s0 as an upstream interface where the
DHCPv6 client is running and enp2s0 as a downstream interface where the prefix is
delegated to. The delegated prefixes are distributed by IPv6 Router Advertisement on the
downstream network.

Example 4. A bridge with two enslaved links

# /etc/systemd/network/25-bridge-static.network
[Match]
Name=bridge0

[Network]
Address=192.168.0.15/24
Gateway=192.168.0.1
DNS=192.168.0.1

# /etc/systemd/network/25-bridge-slave-interface-1.network
[Match]
Name=enp2s0

[Network]
Bridge=bridge0

# /etc/systemd/network/25-bridge-slave-interface-2.network
[Match]
Name=wlp3s0

[Network]
Bridge=bridge0

This creates a bridge and attaches devices "enp2s0" and "wlp3s0" to it. The bridge will
have the specified static address and network assigned, and a default route via the
specified gateway will be added. The specified DNS server will be added to the global list
of DNS resolvers.

Example 5. Bridge port with VLAN forwarding

# /etc/systemd/network/25-bridge-slave-interface-1.network
[Match]
Name=enp2s0

[Network]
Bridge=bridge0

[BridgeVLAN]
VLAN=1-32
PVID=42
EgressUntagged=42

[BridgeVLAN]
VLAN=100-200

[BridgeVLAN]
EgressUntagged=300-400

This overrides the configuration specified in the previous example for the interface
"enp2s0", and enables VLAN on that bridge port. VLAN IDs 1-32, 42, 100-400 will be
allowed. Packets tagged with VLAN IDs 42, 300-400 will be untagged when they leave on this
interface. Untagged packets which arrive on this interface will be assigned VLAN ID 42.

Example 6. Various tunnels

/etc/systemd/network/25-tunnels.network
[Match]
Name=ens1

[Network]
Tunnel=ipip-tun
Tunnel=sit-tun
Tunnel=gre-tun
Tunnel=vti-tun

/etc/systemd/network/25-tunnel-ipip.netdev
[NetDev]
Name=ipip-tun
Kind=ipip

/etc/systemd/network/25-tunnel-sit.netdev
[NetDev]
Name=sit-tun
Kind=sit

/etc/systemd/network/25-tunnel-gre.netdev
[NetDev]
Name=gre-tun
Kind=gre

/etc/systemd/network/25-tunnel-vti.netdev
[NetDev]
Name=vti-tun
Kind=vti

This will bring interface "ens1" up and create an IPIP tunnel, a SIT tunnel, a GRE tunnel,
and a VTI tunnel using it.

Example 7. A bond device

# /etc/systemd/network/30-bond1.network
[Match]
Name=bond1

[Network]
DHCP=ipv6

# /etc/systemd/network/30-bond1.netdev
[NetDev]
Name=bond1
Kind=bond

# /etc/systemd/network/30-bond1-dev1.network
[Match]
MACAddress=52:54:00:e9:64:41

[Network]
Bond=bond1

# /etc/systemd/network/30-bond1-dev2.network
[Match]
MACAddress=52:54:00:e9:64:42

[Network]
Bond=bond1

This will create a bond device "bond1" and enslave the two devices with MAC addresses
52:54:00:e9:64:41 and 52:54:00:e9:64:42 to it. IPv6 DHCP will be used to acquire an
address.

Example 8. Virtual Routing and Forwarding (VRF)

Add the "bond1" interface to the VRF master interface "vrf1". This will redirect routes
generated on this interface to be within the routing table defined during VRF creation.
For kernels before 4.8 traffic won't be redirected towards the VRFs routing table unless
specific ip-rules are added.

# /etc/systemd/network/25-vrf.network
[Match]
Name=bond1

[Network]
VRF=vrf1

Example 9. MacVTap

This brings up a network interface "macvtap-test" and attaches it to "enp0s25".

# /lib/systemd/network/25-macvtap.network
[Match]
Name=enp0s25

[Network]
MACVTAP=macvtap-test

Example 10. A Xfrm interface with physical underlying device.

# /etc/systemd/network/27-xfrm.netdev
[NetDev]
Name=xfrm0
Kind=xfrm

[Xfrm]
InterfaceId=7

# /etc/systemd/network/27-eth0.network
[Match]
Name=eth0

[Network]
Xfrm=xfrm0

This creates a "xfrm0" interface and binds it to the "eth0" device. This allows hardware
based ipsec offloading to the "eth0" nic. If offloading is not needed, xfrm interfaces can
be assigned to the "lo" device.

SEE ALSO
systemd(1), systemd-networkd.service(8), systemd.link(5), systemd.netdev(5), systemd-
resolved.service(8)

NOTES
1. RFC 7217
https://tools.ietf.org/html/rfc7217

2. Link-Local Multicast Name Resolution
https://tools.ietf.org/html/rfc4795

3. Multicast DNS
https://tools.ietf.org/html/rfc6762

4. DNS-over-TLS
https://tools.ietf.org/html/rfc7858

5. DNSSEC
https://tools.ietf.org/html/rfc4033

6. IEEE 802.1AB-2016
https://standards.ieee.org/findstds/standard/802.1AB-2016.html

7. ip-sysctl.txt
https://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt

8. RFC 4941
https://tools.ietf.org/html/rfc4941

9. RFC 1027
https://tools.ietf.org/html/rfc1027

10. RFC 6275
https://tools.ietf.org/html/rfc6275

11. RFC 5227
https://tools.ietf.org/html/rfc5227

12. RFC 4862
https://tools.ietf.org/html/rfc4862

13. RFC 3041
https://tools.ietf.org/html/rfc3041

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

15. RFC 4191
https://tools.ietf.org/html/rfc4191

16. RFC 8520
https://tools.ietf.org/html/rfc8520

17. RFC 7844
https://tools.ietf.org/html/rfc7844

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

19. RFC 7084
https://tools.ietf.org/html/rfc7084

20. RFC 3315
https://tools.ietf.org/html/rfc3315#section-17.2.1

21. RFC 4291
https://tools.ietf.org/html/rfc4291#section-2.5.4

22. RFC 1542
https://tools.ietf.org/html/rfc1542

23. RFC 4861
https://tools.ietf.org/html/rfc4861

systemd 249 SYSTEMD.NETWORK(5)

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