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.
Note that not all settings and configurations can be made with .network
files, and that it may be necessary to use systemd.link(5)) or
systemd.netdev(5)) files in conjuction with .network files when working
with physical and virtual network devices respectively.
The .network files are read from the files located in the system network
directories /usr/lib/systemd/network and /usr/local/lib/systemd/network
[1], 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
alphanumeric order, regardless of the directories in which they live.
However, files with identical filenames replace each other. It is
recommended that each filename is prefixed with a number smaller than
"70" (e.g. 10-eth0.network). Otherwise, the default .network files or
those generated by systemd-network-generator.service(8) may take
precedence over user configured files. 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 /usr/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 /usr/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 interface; and a [Network]
section specifying how the interface should be configured. The first (in
alphanumeric order) of the network files that matches a given interface
is applied, all later files are ignored, even if they match as well.
Note that any network interfaces that have the ID_NET_MANAGED_BY= udev
property set will never be matched by any .network files – unless the
property's value is the string "io.systemd.Network" – even if the
[Match] section would otherwise match. This may be used to exclude
specific network interfaces from systemd-networkd(8)'s management, while
keeping the [Match] section generic. The ID_NET_MANAGED_BY= property
thus declares intended ownership of the device, and permits ensuring
that concurrent network management implementations do not compete for
management of specific devices.
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. The acceptable
formats are:
colon-delimited hexadecimal
Each field must be one byte. E.g. "12:34:56:78:90:ab" or
"AA:BB:CC:DD:EE:FF".
Added in version 250.
hyphen-delimited hexadecimal
Each field must be one byte. E.g. "12-34-56-78-90-ab" or
"AA-BB-CC-DD-EE-FF".
Added in version 250.
dot-delimited hexadecimal
Each field must be two bytes. E.g. "1234.5678.90ab" or
"AABB.CCDD.EEFF".
Added in version 250.
IPv4 address format
E.g. "127.0.0.1" or "192.168.0.1".
Added in version 250.
IPv6 address format
E.g. "2001:0db8:85a3::8a2e:0370:7334" or "::1".
Added in version 250.
The total length of each MAC address must be 4 (for IPv4 tunnel), 6
(for Ethernet), 16 (for IPv6 tunnel), or 20 (for InfiniBand). 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. Defaults to
unset.
Added in version 211.
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,
or IPv4 or IPv6 address format. 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. Defaults to unset.
Added in version 245.
Path=
A whitespace-separated list of shell-style globs matching the
persistent path, as exposed by the udev property ID_PATH.
Added in version 211.
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.
Added in version 211.
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.
Added in version 211.
Kind=
A whitespace-separated list of shell-style globs matching the device
kind, as exposed by networkctl status INTERFACE or ip -d link show
INTERFACE. If the list is prefixed with a "!", the test is inverted.
Some valid values are "bond", "bridge", "gre", "tun", "veth". Valid
kinds are given by netlink's "IFLA_INFO_KIND" attribute, so this is
not comprehensive.
Added in version 251.
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.
Added in version 243.
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.
Added in version 211.
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.
Added in version 244.
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.
Added in version 244.
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.
Added in version 244.
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, the previously assigned value is cleared.
Added in version 211.
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, the previously assigned value is
cleared.
Added in version 211.
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, the previously assigned value is
cleared.
Added in version 211.
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, the previously
assigned value is cleared.
Added in version 237.
Credential=
Checks whether the specified credential was passed to the
systemd-udevd.service service. See System and Service Credentials[2]
for details. When prefixed with an exclamation mark ("!"), the
result is negated. If an empty string is assigned, the previously
assigned value is cleared.
Added in version 252.
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, the previously assigned value is cleared.
Added in version 211.
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, the previously assigned value is
cleared.
Added in version 249.
[LINK] SECTION OPTIONS
The [Link] section accepts the following keys:
MACAddress=
The hardware address to set for the device.
Added in version 218.
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.
Added in version 218.
ARP=
Takes a boolean. If set to true, the IPv4 ARP (low-level Address
Resolution Protocol) and IPv6 NDP (Neighbor Discovery Protocol) for
this interface are 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.
Added in version 232.
Multicast=
Takes a boolean. If set to true, the multicast flag on the device is
enabled. Defaults to unset.
Added in version 239.
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.
Added in version 239.
Promiscuous=
Takes a boolean. If set to true, promiscuous mode of the interface
is enabled. Defaults to unset.
If this is set to false for the underlying link of a "passthru" mode
MACVLAN/MACVTAP, the virtual interface will be created with the
"nopromisc" flag set.
Added in version 248.
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.
Added in version 233.
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...2147483647. Defaults to unset.
Added in version 246.
RequiredForOnline=
Takes a boolean, a minimum operational state (e.g., "carrier"), or a
range of operational state separated with a colon (e.g.,
"degraded:routable"). 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,
systemd-networkd-wait-online deems that the interface is online when
the operational state is in the specified range.
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".
The boolean value "yes" is translated as follows;
CAN devices
"carrier",
Added in version 256.
Master devices, e.g. bond or bridge
"degraded-carrier" with RequiredFamilyForOnline=any,
Added in version 256.
Bonding port interfaces
"enslaved",
Added in version 256.
Other interfaces
"degraded".
Added in version 236.
This setting can be overridden by the command line option for
systemd-networkd-wait-online. See systemd-networkd-wait-
online.service(8) for more details.
Added in version 236.
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 "no". Note that
this option has no effect if "RequiredForOnline=no".
Added in version 249.
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.
Added in version 248.
[SR-IOV] SECTION OPTIONS
SR-IOV provides the ability to partition a single physical PCI resource
into virtual PCI functions which can then be e.g. injected into a VM. In
the case of network VFs, SR-IOV reduces latency and CPU utilisation for
north-south network traffic (that is, traffic with endpoints outside the
host machine), by allowing traffic to bypass the host machine’s network
stack.
The presence of an [SR-IOV] section in a .link file will cause the
creation and configuration of the specified virtual function. Within a
.network file, the specified virtual function will be configured, but
must already exist. Specify several [SR-IOV] sections to configure
several SR-IOVs.
The [SR-IOV] section accepts the following keys.
VirtualFunction=
Specifies a Virtual Function (VF), lightweight PCIe function
designed solely to move data in and out. Takes an integer in the
range 0...2147483646. This option is compulsory.
Added in version 251.
VLANId=
Specifies VLAN ID of the virtual function. Takes an integer in the
range 1...4095.
Added in version 251.
QualityOfService=
Specifies quality of service of the virtual function. Takes an
integer in the range 1...4294967294.
Added in version 251.
VLANProtocol=
Specifies VLAN protocol of the virtual function. Takes "802.1Q" or
"802.1ad".
Added in version 251.
MACSpoofCheck=
Takes a boolean. Controls the MAC spoof checking. When unset, the
kernel's default will be used.
Added in version 251.
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.
Added in version 251.
Trust=
Takes a boolean. Allows one 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.
Added in version 251.
LinkState=
Allows one 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.
Added in version 251.
MACAddress=
Specifies the MAC address for the virtual function.
Added in version 251.
[NETWORK] SECTION OPTIONS
The [Network] section accepts the following keys:
Description=
A description of the device. This is only used for presentation
purposes.
Added in version 211.
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
Advertisements, if reception is enabled, regardless of this
parameter. By explicitly enabling DHCPv6 support here, the DHCPv6
client will be started in the mode specified by the WithoutRA=
setting in the [DHCPv6] section, 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 is not used for name resolution. See option UseDomains= below.
See the [DHCPv4] or [DHCPv6] sections below for further
configuration options for the DHCP client support.
Added in version 211.
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.
Even if this is enabled, the DHCP server will not be started
automatically and wait for the persistent storage being ready to
load/save leases in the storage, unless RelayTarget= or
PersistLeases=no are specified in the [DHCPServer] section. It will
be started after systemd-networkd-persistent-storage.service is
started, which calls networkctl persistent-storage yes. See
networkctl(1) for more details.
Added in version 215.
LinkLocalAddressing=
Enables link-local address autoconfiguration. Accepts a boolean,
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 KeepMaster= or Bridge= is set or when the
specified MACVLAN=/MACVTAP= has Mode=passthru, or ipv6 otherwise.
Added in version 219.
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.
Added in version 246.
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.
Added in version 249.
IPv4LLStartAddress=
Specifies the first IPv4 link-local address to try. Takes an IPv4
address for example 169.254.1.2, from the link-local address range:
169.254.0.0/16 except for 169.254.0.0/24 and 169.254.255.0/24. This
setting may be useful if the device should always have the same
address as long as there is no address conflict. When unset, a
random address will be automatically selected. Defaults to unset.
Added in version 252.
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.
Added in version 216.
DefaultRouteOnDevice=
Takes a boolean. If set to true, sets up the IPv4 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
If you'd like to create an IPv6 default route bound to the
interface, please use the following:
[Route]
Gateway=::
Table=1234
Added in version 243.
LLMNR=
Takes a boolean or "resolve". When true, enables Link-Local
Multicast Name Resolution[3] 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).
Added in version 216.
MulticastDNS=
Takes a boolean or "resolve". When true, enables Multicast DNS[4]
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).
Added in version 229.
DNSOverTLS=
Takes a boolean or "opportunistic". When true, enables
DNS-over-TLS[5] 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 unset, and the global setting will
be used. This setting is read by systemd-resolved.service(8).
Added in version 239.
DNSSEC=
Takes a boolean or "allow-downgrade". When true, enables DNSSEC[6]
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 unset, and the global setting will be used. This setting
is read by systemd-resolved.service(8).
Added in version 229.
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).
Added in version 229.
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.
Added in version 219.
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[7].
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.
Added in version 230.
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".
Added in version 220.
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.
If an IPv4 link-local address (169.254.0.0/16) is specified, IPv4
Address Conflict Detection (RFC 5227[8]) is enabled for the address.
To assign an IPv4 link-local address without IPv4 Address Conflict
Detection, please use [Address] section to configure the address and
disable DuplicateAddressDetection=.
[Address]
Address=169.254.10.1/24
DuplicateAddressDetection=none
If an empty string is specified, then the all previous assignments
in both [Network] and [Address] sections are cleared.
Added in version 211.
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.
Added in version 211.
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).
Added in version 211.
UseDomains=
Specifies the protocol-independent default value for the same
settings in [IPv6AcceptRA], [DHCPv4], and [DHCPv6] sections below.
Takes a boolean, or the special value route. See also the same
setting in [DHCPv4] below. Defaults to unset.
Added in version 256.
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.
Added in version 216.
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.
Added in version 240.
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).
Added in version 216.
IPv4Forwarding=
Configures IPv4 packet forwarding for the interface. Takes a boolean
value. This controls the net.ipv4.conf.INTERFACE.forwarding sysctl
option of the network interface. See IP Sysctl[9] for more details
about the sysctl option. Defaults to true if IPMasquerade= is
enabled for IPv4, otherwise the value specified to the same setting
in networkd.conf(5) will be used. If none of them are specified, the
sysctl option will not be changed.
To control the global setting, use the same setting in
networkd.conf(5).
Added in version 256.
IPv6Forwarding=
Configures interface-specific host/router behaviour. Takes a boolean
value. This controls the net.ipv6.conf.INTERFACE.forwarding sysctl
option of the network interface. See IP Sysctl[9] for more details
about the sysctl option. Defaults to true if IPMasquerade= is
enabled for IPv6 or IPv6SendRA= is enabled, otherwise the value
specified to the same setting in networkd.conf(5) will be used. If
none of them are specified, the sysctl option will not be changed.
To control the global setting, use the same setting in
networkd.conf(5).
Note, unlike IPv4Forwarding=, enabling per-interface IPv6Forwarding=
on two or more interfaces DOES NOT make IPv6 packets forwarded
within the interfaces. This setting just controls the per-interface
sysctl value, and the sysctl value is not directly correlated to
whether packets are forwarded. To ensure IPv6 packets forwarded, the
global setting in networkd.conf(5) needs to be enabled.
Added in version 256.
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. Typically, this should be enabled on the
downstream interface of routers. Takes one of "ipv4", "ipv6",
"both", or "no". Defaults to "no". Note that any positive boolean
values such as "yes" or "true" are now deprecated. Please use one of
the values above. Specifying "ipv4" or "both" implies
IPv4Forwarding= settings in both .network file for this interface
and the global networkd.conf(5) unless they are explicitly
specified. Similarly for IPv6Forwarding= when "ipv6" or "both" is
specified. See IPv4Forwarding=/IPv6Forwarding= in the above for the
per-link settings, and networkd.conf(5) for the global settings.
Added in version 219.
IPv6PrivacyExtensions=
Configures use of stateless temporary addresses that change over
time (see RFC 4941[10], 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. When unspecified, the value specified
in the same setting in networkd.conf(5), which defaults to "no",
will be used.
Added in version 222.
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. Defaults to false for bridge
devices, when IPv6Forwarding=, IPv6SendRA=, or KeepMaster= is
enabled. Otherwise, enabled by default. Cannot be enabled on devices
aggregated in a bond device or 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[9] 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.
Added in version 231.
IPv6DuplicateAddressDetection=
Configures the amount of IPv6 Duplicate Address Detection (DAD)
probes to send. When unset, the kernel's default will be used.
Added in version 228.
IPv6HopLimit=
Configures IPv6 Hop Limit. Takes an integer in the range 1...255.
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.
Added in version 228.
IPv6RetransmissionTimeSec=
Configures IPv6 Retransmission Time. The time between retransmitted
Neighbor Solicitation messages. Used by address resolution and the
Neighbor Unreachability Detection algorithm. A value of zero is
ignored and the kernel's current value will be used. Defaults to
unset, and the kernel's current value will be used.
Added in version 256.
IPv4ReversePathFilter=
Configure IPv4 Reverse Path Filtering. If enabled, when an IPv4
packet is received, the machine will first check whether the source
of the packet would be routed through the interface it came in. If
there is no route to the source on that interface, the machine will
drop the packet. Takes one of "no", "strict", or "loose". When "no",
no source validation will be done. When "strict", each incoming
packet is tested against the FIB and if the incoming interface is
not the best reverse path, the packet check will fail. By default,
failed packets are discarded. When "loose", each incoming packet's
source address is tested against the FIB. The packet is dropped only
if the source address is not reachable via any interface on that
router. See RFC 3704[11]. When unset, the kernel's default will be
used.
Added in version 255.
MulticastIGMPVersion=
Configures IPv4 Multicast IGMP Version to be used, and controls the
value of /proc/sys/net/ipv4/conf/INTERFACE/force_igmp_version. Takes
one of "no", "v1", "v2", or "v3". When "no", no enforcement of an
IGMP version is applied. IGMPv1/v2 fallbacks are allowed, and
systemd-networkd will return to IGMPv3 mode after all IGMPv1/v2
Querier Present timers have expired. When "v1", use of IGMP version
1 is enforced. An IGMPv1 report will be returned even if IGMPv2/v3
queries are received. When "v2", use of IGMP version 2 is enforced.
An IGMPv2 report will be returned if an IGMPv2/v3 query is received.
systemd-networkd will fall back to IGMPv1 if an IGMPv1 query is
received. When "v3", use of IGMP version 3 is enforced, and the
response is the same as with "no". Defaults to unset — the sysctl is
not set.
Added in version 257.
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.
Added in version 246.
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.
Added in version 248.
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[11]. When unset, the kernel's default will
be used.
Added in version 233.
IPv4ProxyARPPrivateVLAN=
Takes a boolean. Configures proxy ARP private VLAN for IPv4, also
known as VLAN aggregation, private VLAN, source-port filtering,
port-isolation, or MAC-forced forwarding.
This variant of the ARP proxy technique will allow the ARP proxy to
reply back to the same interface.
See RFC 3069[12]. When unset, the kernel's default will be used.
Added in version 256.
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.
Added in version 234.
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 setting implies
IPv6ProxyNDP=yes but has no effect if IPv6ProxyNDP= has been set to
false. When unset, the kernel's default will be used.
Added in version 233.
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 the [IPv6RoutePrefix]
sections are distributed as defined in the [IPv6SendRA] section. If
DHCPPrefixDelegation= is enabled, then the delegated prefixes are
also distributed. See DHCPPrefixDelegation= setting and the
[IPv6SendRA], [IPv6Prefix], [IPv6RoutePrefix], and
[DHCPPrefixDelegation] sections for more configuration options.
If enabled, IPv6Forwarding= on this interface is also enabled,
unless the setting is explicitly specified. See IPv6Forwarding= in
the above for more details.
Added in version 247.
DHCPPrefixDelegation=
Takes a boolean value. When enabled, requests subnet prefixes on
another link via the DHCPv6 protocol or via the 6RD option in the
DHCPv4 protocol. An address within each delegated prefix will be
assigned, and the prefixes will be announced through IPv6 Router
Advertisement if IPv6SendRA= is enabled. This behaviour can be
configured in the [DHCPPrefixDelegation] section. Defaults to
disabled.
Added in version 250.
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.
Added in version 239.
KeepMaster=
Takes a boolean value. When enabled, the current master interface
index will not be changed, and BatmanAdvanced=, Bond=, Bridge=, and
VRF= settings are ignored. This may be useful when a netdev with a
master interface is created by another program, e.g. systemd-
nspawn(1). Defaults to false.
Added in version 250.
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).
Added in version 211.
IPoIB=, IPVLAN=, IPVTAP=, MACsec=, MACVLAN=, MACVTAP=, Tunnel=, VLAN=,
VXLAN=, Xfrm=
The name of an IPoIB, IPVLAN, IPVTAP, 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.
Added in version 211.
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.
Added in version 235.
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.
Added in version 235.
ConfigureWithoutCarrier=
Takes a boolean. Allows systemd-networkd to configure a specific
link even if it has no carrier. Defaults to false. If enabled, and
the IgnoreCarrierLoss= setting is not explicitly set, then it is
enabled as well.
With this enabled, to make the interface enter the "configured"
state, which is required to make systemd-networkd-wait-online work
properly for the interface, all dynamic address configuration
mechanisms like DHCP= and IPv6AcceptRA= (which is enabled by default
in most cases) need to be disabled. Also, DuplicateAddressDetection=
(which is enabled by default for IPv4 link-local addresses and all
IPv6 addresses) needs to be disabled for all static address
configurations. Otherwise, without carrier, the interface will be
stuck in the "configuring" state, and systemd-networkd-wait-online
for the interface will timeout. Also, it is recommended to set
RequiredForOnline=no-carrier to make systemd-networkd-wait-online
work for the interface.
Added in version 235.
IgnoreCarrierLoss=
Takes a boolean or a timespan. When true, systemd-networkd retains
both the static and dynamic configuration of the interface even if
its carrier is lost. When false, systemd-networkd drops both the
static and dynamic configuration of the interface. When a timespan
is specified, systemd-networkd waits for the specified timespan, and
ignores the carrier loss if the link regain its carrier within the
timespan. Setting 0 seconds is equivalent to "no", and "infinite" is
equivalent to "yes".
Setting a finite timespan may be useful when e.g. in the following
cases:
• A wireless interface connecting to a network which has multiple
access points with the same SSID.
• Enslaving a wireless interface to a bond interface, which may
disconnect from the connected access point and causes its
carrier to be lost.
• The driver of the interface resets when the MTU is changed.
When Bond= is specified to a wireless interface, defaults to 3
seconds. When the DHCPv4 client is enabled and UseMTU= in the
[DHCPv4] section enabled, defaults to 5 seconds. Otherwise, defaults
to the value specified with ConfigureWithoutCarrier=. When
ActivationPolicy= is set to "always-up", this is forced to "yes",
and ignored any user specified values.
Added in version 242.
KeepConfiguration=
Takes a boolean or one of "static", "dynamic-on-stop", and
"dynamic". When "static", systemd-networkd will not drop statically
configured addresses and routes on starting up process. When
"dynamic-on-stop", the dynamically configurad addresses and routes,
such as DHCPv4, DHCPv6, SLAAC, and IPv4 link-local address, will not
be dropped when systemd-networkd is being stopped. When "dynamic",
the dynamically configured addresses and routes will never be
dropped, and the lifetime of DHCPv4 leases will be ignored. 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
"dynamic" implies "dynamic-on-stop", and "yes" implies "dynamic" and
"static". Defaults to "dynamic-on-stop" when systemd-networkd is
running in initrd, "yes" when the root filesystem is a network
filesystem, and "no" otherwise.
Added in version 257.
[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 setting is mandatory. Each
[Address] section can contain one Address= setting.
Added in version 211.
Peer=
The peer address in a point-to-point connection. Accepts the same
format as the Address= setting.
Added in version 216.
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.
Added in version 211.
Label=
Specifies the label for the IPv4 address. The label must be a 7-bit
ASCII string with a length of 1...15 characters. Defaults to unset.
Added in version 211.
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.
Added in version 230.
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 integer in the range
0...255. Defaults to "global". IPv4 only - IPv6 scope is
automatically assigned by the kernel and cannot be set manually.
Added in version 235.
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.
Added in version 246.
HomeAddress=
Takes a boolean. Designates this address the "home address" as
defined in RFC 6275[13]. Supported only on IPv6. Defaults to false.
Added in version 232.
DuplicateAddressDetection=
Takes one of "ipv4", "ipv6", "both", or "none". When "ipv4",
performs IPv4 Address Conflict Detection. See RFC 5227[8]. When
"ipv6", performs IPv6 Duplicate Address Detection. See RFC 4862[14].
Defaults to "ipv4" for IPv4 link-local addresses (169.254.0.0/16),
"ipv6" for IPv6 addresses, and "none" otherwise.
Added in version 232.
ManageTemporaryAddress=
Takes a boolean. If true the kernel manage temporary addresses
created from this one as template on behalf of Privacy Extensions
RFC 3041[15]. 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.
Added in version 232.
AddPrefixRoute=
Takes a boolean. When true, the prefix route for the address is
automatically added. Defaults to true.
Added in version 245.
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
systemd-networkd's netdev kind vxlan have the group option that
enables them 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".
Added in version 232.
NetLabel=label
This setting provides a method for integrating static and dynamic
network configuration into Linux NetLabel[16] subsystem rules, used
by Linux Security Modules (LSMs)[17] for network access control. The
label, with suitable LSM rules, can be used to control connectivity
of (for example) a service with peers in the local network. At least
with SELinux, only the ingress can be controlled but not egress. The
benefit of using this setting is that it may be possible to apply
interface independent part of NetLabel configuration at very early
stage of system boot sequence, at the time when the network
interfaces are not available yet, with netlabelctl(8), and the
per-interface configuration with systemd-networkd once the
interfaces appear later. Currently this feature is only implemented
for SELinux.
The option expects a single NetLabel label. The label must conform
to lexical restrictions of LSM labels. When an interface is
configured with IP addresses, the addresses and subnetwork masks
will be appended to the NetLabel Fallback Peer Labeling[18] rules.
They will be removed when the interface is deconfigured. Failures to
manage the labels will be ignored.
Warning
Once labeling is enabled for network traffic, a lot of LSM
access control points in Linux networking stack go from dormant
to active. Care should be taken to avoid getting into a
situation where for example remote connectivity is broken, when
the security policy has not been updated to consider LSM
per-packet access controls and no rules would allow any network
traffic. Also note that additional configuration with
netlabelctl(8) is needed.
Example:
[Address]
NetLabel=system_u:object_r:localnet_peer_t:s0
With the example rules applying for interface "eth0", when the
interface is configured with an IPv4 address of 10.0.0.123/8,
systemd-networkd performs the equivalent of netlabelctl operation
netlabelctl unlbl add interface eth0 address:10.0.0.0/8 label:system_u:object_r:localnet_peer_t:s0
and the reverse operation when the IPv4 address is deconfigured. The
configuration can be used with LSM rules; in case of SELinux to
allow a SELinux domain to receive data from objects of SELinux
"peer" class. For example:
type localnet_peer_t;
allow my_server_t localnet_peer_t:peer recv;
The effect of the above configuration and rules (in absence of other
rules as may be the case) is to only allow "my_server_t" (and
nothing else) to receive data from local subnet 10.0.0.0/8 of
interface "eth0".
Added in version 252.
NFTSet=source:family:table:set
This setting provides a method for integrating network configuration
into firewall rules with NFT[19] sets. The benefit of using the
setting is that static network configuration (or dynamically
obtained network addresses, see similar directives in other
sections) can be used in firewall rules with the indirection of NFT
set types. For example, access could be granted for hosts in the
local subnetwork only. Firewall rules using IP address of an
interface are also instantly updated when the network configuration
changes, for example via DHCP.
This option expects a whitespace separated list of NFT set
definitions. Each definition consists of a colon-separated tuple of
source type (one of "address", "prefix" or "ifindex"), NFT address
family (one of "arp", "bridge", "inet", "ip", "ip6", or "netdev"),
table name and set name. The names of tables and sets must conform
to lexical restrictions of NFT table names. The type of the element
used in the NFT filter must match the type implied by the directive
("address", "prefix" or "ifindex") and address type (IPv4 or IPv6)
as shown in the table below.
Table 1. Defined source type values
┌─────────────┬─────────────────┬───────────────────┐
│ Source type │ Description │ Corresponding NFT │
│ │ │ type name │
├─────────────┼─────────────────┼───────────────────┤
│ "address" │ host IP address │ "ipv4_addr" or │
│ │ │ "ipv6_addr" │
├─────────────┼─────────────────┼───────────────────┤
│ "prefix" │ network prefix │ "ipv4_addr" or │
│ │ │ "ipv6_addr", with │
│ │ │ "flags interval" │
├─────────────┼─────────────────┼───────────────────┤
│ "ifindex" │ interface index │ "iface_index" │
└─────────────┴─────────────────┴───────────────────┘
When an interface is configured with IP addresses, the addresses,
subnetwork masks or interface index will be appended to the NFT
sets. The information will be removed when the interface is
deconfigured. systemd-networkd only inserts elements to (or removes
from) the sets, so the related NFT rules, tables and sets must be
prepared elsewhere in advance. Failures to manage the sets will be
ignored.
Example:
[Address]
NFTSet=prefix:netdev:filter:eth_ipv4_prefix
Corresponding NFT rules:
table netdev filter {
set eth_ipv4_prefix {
type ipv4_addr
flags interval
}
chain eth_ingress {
type filter hook ingress device "eth0" priority filter; policy drop;
ip daddr != @eth_ipv4_prefix drop
accept
}
}
Added in version 255.
[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.
Added in version 240.
LinkLayerAddress=
The link layer address (MAC address or IP address) of the neighbor.
Added in version 243.
[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[20].
Precedence is managed by userspace, and only the label itself is stored
in the kernel.
Label=
The label for the prefix. Takes an unsigned integer in the range
0...4294967294 (0xfffffffe). 4294967295 (0xffffffff) is reserved.
This setting is mandatory.
Added in version 234.
Prefix=
Takes an IPv6 address with a prefix length, separated by a slash "/"
character. This setting is mandatory.
Added in version 234.
[ROUTINGPOLICYRULE] SECTION OPTIONS
An [RoutingPolicyRule] section accepts the following settings. Specify
several [RoutingPolicyRule] sections to configure several rules.
TypeOfService=
This specifies the Type of Service (ToS) field of packets to match;
it takes an unsigned integer in the range 0...255. The field can be
used to specify precedence (the first 3 bits) and ToS (the next 3
bits). The field can be also used to specify Differentiated Services
Code Point (DSCP) (the first 6 bits) and Explicit Congestion
Notification (ECN) (the last 2 bits). See Type of Service[21] and
Differentiated services[22] for more details.
Added in version 235.
From=
Specifies the source address prefix to match. Possibly followed by a
slash and the prefix length.
Added in version 235.
To=
Specifies the destination address prefix to match. Possibly followed
by a slash and the prefix length.
Added in version 235.
FirewallMark=
Specifies the iptables firewall mark value to match (a number in the
range 0...4294967295). Optionally, the firewall mask (also a number
between 0...4294967295) can be suffixed with a slash ("/"), e.g.,
"7/255". When the mark value is non-zero and no mask is explicitly
specified, all bits of the mark are compared.
Added in version 235.
Table=
Specifies the routing table identifier to look up 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". Ignored if
L3MasterDevice= is true.
Added in version 235.
Priority=
Specifies the priority of this rule. Priority= is an 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.
Added in version 235.
GoTo=
Specifies the target priority used by the "goto" type of rule. Takes
an integer in the range 1...4294967295. This must be larger than the
priority of the rule specified in Priority=. When specified,
Type=goto is implied. This is mandatory when Type=goto.
Added in version 257.
IncomingInterface=
Specifies incoming device to match. If the interface is loopback,
the rule only matches packets originating from this host.
Added in version 236.
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.
Added in version 236.
L3MasterDevice=
Takes a boolean. Specifies whether the rule is to direct lookups to
the tables associated with level 3 master devices (also known as
Virtual Routing and Forwarding or VRF devices). For further details
see Virtual Routing and Forwarding (VRF)[23]. Defaults to false.
Added in version 256.
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.
Added in version 240.
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.
Added in version 240.
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.
Added in version 240.
InvertRule=
A boolean. Specifies whether the rule is to be inverted. Defaults to
false.
Added in version 240.
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".
Added in version 243.
User=
Takes a username, a user ID, or a range of user IDs separated by a
dash. Defaults to unset.
Added in version 245.
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.
Added in version 245.
SuppressInterfaceGroup=
Takes an integer in the range 0...2147483647 and rejects routing
decisions that have an interface with the same group id. It has the
same meaning as suppress_ifgroup in ip rule. Defaults to unset.
Added in version 250.
Type=
Specifies Routing Policy Database (RPDB) rule type. Takes one of
"table", "goto", "nop", "blackhole", "unreachable", or "prohibit".
When "goto", the target priority must be specified in GoTo=.
Defaults to "table".
Added in version 248.
[NEXTHOP] SECTION OPTIONS
The [NextHop] section is used to manipulate entries in the kernel's
"nexthop" tables. The [NextHop] section accepts the following settings.
Specify several [NextHop] sections to configure several hops.
Id=
The id of the next hop. Takes an integer in the range
1...4294967295. This is mandatory if ManageForeignNextHops=no is
specified in networkd.conf(5). Otherwise, if unspecified, an unused
ID will be automatically picked.
Added in version 244.
Gateway=
As in the [Network] section.
Added in version 244.
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".
Added in version 248.
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".
Added in version 248.
Blackhole=
Takes a boolean. If enabled, packets to the corresponding routes are
discarded silently, and Gateway= cannot be specified. Defaults to
"no".
Added in version 248.
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.
Added in version 249.
[ROUTE] SECTION OPTIONS
The [Route] section accepts the following settings. 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.
Added in version 211.
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".
Added in version 234.
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.
Added in version 211.
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.
Added in version 218.
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.
Added in version 216.
IPv6Preference=
Specifies the route preference as defined in RFC 4191[24] 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.
Added in version 234.
Scope=
The scope of the IPv4 route, which can be "global", "site", "link",
"host", or "nowhere":
• "global" means the route can reach hosts more than one hop away.
• "site" means an interior route in the local autonomous system.
• "link" means the route can only reach hosts on the local network
(one hop away).
• "host" means the route will not leave the local machine (used
for internal addresses like 127.0.0.1).
• "nowhere" means the destination does not exist.
For IPv4 route, defaults to "host" if Type= is "local" or "nat", and
"link" if Type= is "broadcast", "multicast", "anycast", or
"unicast". In other cases, defaults to "global". The value is not
used for IPv6.
Added in version 219.
PreferredSource=
The preferred source address of the route. The address must be in
the format described in inet_pton(3).
Added in version 227.
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".
Added in version 230.
HopLimit=
Configures per route hop limit. Takes an integer in the range
1...255. See also IPv6HopLimit=.
Added in version 255.
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".
Added in version 234.
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".
Added in version 235.
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.
Added in version 237.
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.
Added in version 237.
QuickAck=
Takes a boolean. When true, the TCP quick ACK mode for the route is
enabled. When unset, the kernel's default will be used.
Added in version 237.
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.
Added in version 243.
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.
Added in version 239.
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.
Added in version 248.
TCPCongestionControlAlgorithm=
Specifies the TCP congestion control algorithm for the route. Takes
a name of the algorithm, e.g. "bbr", "dctcp", or "vegas". When
unset, the kernel's default will be used.
Added in version 252.
TCPRetransmissionTimeoutSec=
Specifies the TCP Retransmission Timeout (RTO) for the route. Takes
time values in seconds. This value specifies the timeout of an alive
TCP connection, when retransmissions remain unacknowledged. When
unset, the kernel's default will be used.
Added in version 255.
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.
Added in version 245.
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.
Added in version 248.
[DHCPV4] SECTION OPTIONS
The [DHCPv4] section configures the DHCPv4 client, if it is enabled with
the DHCP= setting described above:
RequestAddress=
Takes an IPv4 address. When specified, the Requested IP Address
option (option code 50) is added with it to the initial DHCPDISCOVER
message sent by the DHCP client. Defaults to unset, and an already
assigned dynamic address to the interface is automatically picked.
Added in version 255.
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.
Added in version 215.
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.
Added in version 223.
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[25].
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.
Added in version 246.
ClientIdentifier=
The DHCPv4 client identifier to use. Takes one of mac or duid. 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, is used. IAID can be configured by IAID=. DUID can be
configured by DUIDType= and DUIDRawData=. Defaults to duid.
Added in version 220.
VendorClassIdentifier=
The vendor class identifier used to identify vendor type and
configuration.
Added in version 216.
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.
Added in version 239.
DUIDType=
Override the global DUIDType= setting for this network. See
networkd.conf(5) for a description of possible values.
Added in version 230.
DUIDRawData=
Override the global DUIDRawData= setting for this network. See
networkd.conf(5) for a description of possible values.
Added in version 230.
IAID=
The DHCP Identity Association Identifier (IAID) for the interface, a
32-bit unsigned integer.
Added in version 230.
RapidCommit=
Takes a boolean. The DHCPv4 client can obtain configuration
parameters from a DHCPv4 server through a rapid two-message exchange
(discover and ack). When the rapid commit option is set by both the
DHCPv4 client and the DHCPv4 server, the two-message exchange is
used. Otherwise, the four-message exchange (discover, offer,
request, and ack) is used. The two-message exchange provides faster
client configuration. See RFC 4039[26] for details. Defaults to true
when Anonymize=no and neither AllowList= nor DenyList= is specified,
and false otherwise.
Added in version 255.
Anonymize=
Takes a boolean. When true, the options sent to the DHCP server will
follow the RFC 7844[27] (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, ClientIdentifier=mac, RapidCommit=no, SendHostname=no,
Use6RD=no, UseCaptivePortal=no, UseMTU=no, UseNTP=no, UseSIP=no, and
UseTimezone=no are implied and these settings in the .network file
are silently ignored. Also, Hostname=, MUDURL=, RequestAddress=,
RequestOptions=, SendOption=, SendVendorOption=, UserClass=, and
VendorClassIdentifier= are silently 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.
Added in version 235.
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.
Added in version 244.
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[28]. This setting can be
specified multiple times. If an empty string is specified, then all
options specified earlier are cleared. Defaults to unset.
Added in version 244.
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[28]. This setting can be
specified multiple times. If an empty string is specified, then all
options specified earlier are cleared. Defaults to unset.
Added in version 246.
IPServiceType=
Takes one of the special values "none", "CS6", or "CS4". When "none"
no IP service type is set to the packet sent from the DHCPv4 client.
When "CS6" (network control) or "CS4" (realtime), the corresponding
service type will be set. Defaults to "CS6".
Added in version 244.
SocketPriority=
The Linux socket option SO_PRIORITY applied to the raw IP socket
used for initial DHCPv4 messages. Unset by default. Usual values
range from 0 to 6. More details about SO_PRIORITY socket option in
socket(7). Can be used in conjunction with [VLAN] section
EgressQOSMaps= setting of .netdev file to set the 802.1Q VLAN
ethernet tagged header priority, see systemd.netdev(5).
Added in version 253.
Label=
Specifies the label for the IPv4 address received from the DHCP
server. The label must be a 7-bit ASCII string with a length of
1...15 characters. Defaults to unset.
Added in version 250.
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).
Added in version 211.
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.
Added in version 243.
UseNTP=
When true (the default), the NTP servers received from the DHCP
server will be used by systemd-timesyncd.service.
Added in version 220.
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.
Added in version 249.
UseSIP=
When true (the default), the SIP servers received from the DHCP
server will be collected and made available to client programs.
Added in version 244.
UseCaptivePortal=
When true (the default), the captive portal advertised by the DHCP
server will be recorded and made available to client programs and
displayed in the networkctl(1) status output per-link.
Added in version 254.
UseDNR=
When true, designated resolvers advertised by the DHCP server will
be used as encrypted DNS servers. See RFC 9463[29].
Defaults to unset, and the value for UseDNS= will be used.
Added in version 257.
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.
Note, some drivers will reset the interfaces if the MTU is changed.
For such interfaces, please try to use IgnoreCarrierLoss= with a
short timespan, e.g. "3 seconds".
Added in version 211.
UseHostname=
When true (the default), the hostname received from the DHCP server
will be set as the transient hostname of the system.
Added in version 211.
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, similarly 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, similarly
to the effect of the Domains= setting when the argument is prefixed
with "~".
When unspecified, the value specified in the same setting in the
[Network] section will be used. When it is unspecified, the value
specified in the same setting in the [DHCPv4] section in
networkd.conf(5) will be used. When it is unspecified, the value
specified in the same setting in the [Network] section in
networkd.conf(5) will be used. When none of them are specified,
defaults to "no".
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).
Added in version 216.
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.
Added in version 215.
RouteMetric=
Set the routing metric for routes specified by the DHCP server
(including the prefix route added for the specified prefix). Takes
an unsigned integer in the range 0...4294967295. Defaults to 1024.
Added in version 217.
RouteTable=num
The table identifier for DHCP routes. Takes one of predefined names
"default", "main", and "local", and names defined in RouteTable= in
networkd.conf(5), or a number between 1...4294967295.
When used in combination with VRF=, the VRF's routing table is used
when this parameter is not specified.
Added in version 232.
RouteMTUBytes=
Specifies the MTU for the DHCP routes. Please see the [Route]
section for further details.
Added in version 245.
QuickAck=
Takes a boolean. When true, the TCP quick ACK mode is enabled for
the routes configured by the acquired DHCPv4 lease. When unset, the
kernel's default will be used.
Added in version 253.
InitialCongestionWindow=
As in the [Route] section.
Added in version 255.
InitialAdvertisedReceiveWindow=
As in the [Route] section.
Added in version 255.
UseGateway=
When true, and the DHCP server provides a Router option, the default
gateway based on the router address will be configured. Defaults to
unset, and the value specified with UseRoutes= will be used.
Note, when the server provides both the Router and Classless Static
Routes option, and UseRoutes= is enabled, the Router option is
always ignored regardless of this setting. See RFC 3442[30].
Added in version 246.
UseTimezone=
When true, the timezone received from the DHCP server will be set as
timezone of the local system. Defaults to false.
Added in version 226.
Use6RD=
When true, subnets of the received IPv6 prefix are assigned to
downstream interfaces which enables DHCPPrefixDelegation=. See also
DHCPPrefixDelegation= in the [Network] section, the
[DHCPPrefixDelegation] section, and RFC 5969[31]. Defaults to false.
Added in version 250.
UnassignedSubnetPolicy=
Takes "none", or one of the reject types: "unreachable", "prohibit",
"blackhole", or "throw". If a reject type is specified, the reject
route corresponding to the acquired 6RD prefix will be configured.
For example, when "unreachable",
unreachable 2001:db8::/56 dev lo proto dhcp metric 1024 pref medium
will be configured. See RFC 7084[32]. If "none" is specified, such
route will not be configured. This may be useful when custom
firewall rules that handle packets for unassigned subnets will be
configured. Defaults to "unreachable".
Added in version 257.
IPv6OnlyMode=
When true, the DHCPv4 configuration will be delayed by the timespan
provided by the DHCP server and skip to configure dynamic IPv4
network connectivity if IPv6 connectivity is provided within the
timespan. See RFC 8925[33]. Defaults to false.
Added in version 255.
FallbackLeaseLifetimeSec=
Allows one to set DHCPv4 lease lifetime when DHCPv4 server does not
send the lease lifetime. Takes one of "forever" or "infinity". If
specified, the acquired address never expires. Defaults to unset.
Added in version 246.
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.
Added in version 216.
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.
Added in version 243.
ListenPort=
Set the port from which the DHCP client packets originate.
Added in version 233.
ServerPort=
Set the port on which the DHCP server is listening.
Added in version 256.
DenyList=
A whitespace-separated list of IPv4 addresses. Each address can
optionally take a prefix length after "/". DHCP offers from servers
in the list are rejected. Note that if AllowList= is configured then
DenyList= is ignored.
Note that this filters only DHCP offers, so the filtering might not
work when RapidCommit= is enabled. See also RapidCommit= above.
Added in version 246.
AllowList=
A whitespace-separated list of IPv4 addresses. Each address can
optionally take a prefix length after "/". DHCP offers from servers
in the list are accepted.
Note that this filters only DHCP offers, so the filtering might not
work when RapidCommit= is enabled. See also RapidCommit= above.
Added in version 246.
SendRelease=
When true, the DHCPv4 client sends a DHCP release packet when it
stops. Defaults to true.
Added in version 243.
SendDecline=
A boolean. When true, systemd-networkd performs IPv4 Duplicate
Address Detection to the acquired address by the DHCPv4 client. If
duplicate is detected, the DHCPv4 client rejects the address by
sending a DHCPDECLINE packet to the DHCP server, and tries to obtain
an IP address again. See RFC 5227[8]. Defaults to false.
Added in version 245.
NetLabel=
This applies the NetLabel for the addresses received with DHCP, like
NetLabel= in [Address] section applies it to statically configured
addresses. See NetLabel= in [Address] section for more details.
Added in version 252.
NFTSet=
This applies the NFT set for the network configuration received with
DHCP, like NFTSet= in [Address] section applies it to static
configuration. See NFTSet= in [Address] section for more details.
For "address" or "prefix" source types, the type of the element used
in the NFT filter must be "ipv4_addr".
Added in version 255.
[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.
Added in version 246.
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.
Added in version 246.
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[28]. This setting
can be specified multiple times. If an empty string is specified,
then all options specified earlier are cleared. Defaults to unset.
Added in version 246.
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[28]. 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.
Added in version 246.
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.
Added in version 246.
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.
Added in version 244.
UnassignedSubnetPolicy=
Takes "none" or one of the reject types: "unreachable", "prohibit",
"blackhole", or "throw". If a reject type is specified, the reject
route corresponding to the delegated prefix will be configured. For
example, when "unreachable",
unreachable 2001:db8::/56 dev lo proto dhcp metric 1024 pref medium
will be configured. See RFC 7084[32]. If "none" is specified, such
route will not be configured. This may be useful when custom
firewall rules that handle packets for unassigned subnets will be
configured. Defaults to "unreachable".
Added in version 257.
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 set by both the
DHCPv6 client and the DHCPv6 server, the two-message exchange is
used. Otherwise, the four-message exchange (solicit, advertise,
request, and reply) is used. The two-message exchange provides
faster client configuration. See RFC 3315[34] for details. Defaults
to true, and the two-message exchange will be used if the server
support it.
Added in version 252.
SendHostname=
When true (the default), the machine's hostname (or the value
specified with Hostname=, described below) will be sent to the
DHCPv6 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.
Added in version 255.
Hostname=
Use this value for the hostname which is sent to the DHCPv6 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.
Added in version 255.
UseAddress=
When true (the default), the IP addresses provided by the DHCPv6
server will be assigned.
Added in version 248.
UseCaptivePortal=
When true (the default), the captive portal advertised by the DHCPv6
server will be recorded and made available to client programs and
displayed in the networkctl(1) status output per-link.
Added in version 254.
UseDelegatedPrefix=
When true (the default), the client will request the DHCPv6 server
to delegate prefixes. If the server provides prefixes to be
delegated, then subnets of the prefixes are assigned to the
interfaces that have DHCPPrefixDelegation=yes. See also the
DHCPPrefixDelegation= setting in the [Network] section, settings in
the [DHCPPrefixDelegation] section, and RFC 8415[35].
Added in version 250.
UseDNS=, UseDNR=, UseNTP=, UseHostname=, UseDomains=, NetLabel=,
SendRelease=
As in the [DHCPv4] section.
Added in version 243.
NFTSet=
This applies the NFT set for the network configuration received with
DHCP, like NFTSet= in [Address] section applies it to static
configuration. See NFTSet= in [Address] section for more details.
For "address" or "prefix" source types, the type of the element used
in the NFT filter must be "ipv6_addr".
Added in version 255.
WithoutRA=
Allows DHCPv6 client to start without router advertisements's
"managed" or "other configuration" flag. Takes one of "no",
"solicit", or "information-request". If this is not specified,
"solicit" is used when DHCPPrefixDelegation= is enabled and
UplinkInterface=:self is specified in the [DHCPPrefixDelegation]
section. Otherwise, defaults to "no", and the DHCPv6 client will be
started when an RA is received. See also the DHCPv6Client= setting
in the [IPv6AcceptRA] section.
Added in version 246.
[DHCPPREFIXDELEGATION] SECTION OPTIONS
The [DHCPPrefixDelegation] section configures subnet prefixes of the
delegated prefixes acquired by a DHCPv6 client or by a DHCPv4 client
through the 6RD option on another interface. The settings in this
section are used only when the DHCPPrefixDelegation= setting in the
[Network] section is enabled.
UplinkInterface=
Specifies the name or the index of the uplink interface, or one of
the special values ":self" and ":auto". When ":self", the interface
itself is considered the uplink interface, and WithoutRA=solicit is
implied if the setting is not explicitly specified. When ":auto",
the first link which acquired prefixes to be delegated from the
DHCPv6 or DHCPv4 server is selected. Defaults to ":auto".
Added in version 250.
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[36], section 2.5.4),
in which case the allowed value is hexadecimal, from 0 to
0x7fffffffffffffff inclusive.
Added in version 246.
Announce=
Takes a boolean. When enabled, and IPv6SendRA= in [Network] section
is enabled, the delegated prefixes are distributed through the IPv6
Router Advertisement. This setting will be ignored when the
DHCPPrefixDelegation= setting is enabled on the upstream interface.
Defaults to yes.
Added in version 247.
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 interface), 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.
Added in version 246.
Token=
Specifies an optional address generation mode for assigning an
address in each delegated prefix. This accepts the same syntax as
Token= in the [IPv6AcceptRA] section. If Assign= is set to false,
then this setting will be ignored. Defaults to unset, which means
the EUI-64 algorithm will be used.
Added in version 246.
ManageTemporaryAddress=
As in the [Address] section, but defaults to true.
Added in version 248.
RouteMetric=
The metric of the route to the delegated prefix subnet. Takes an
unsigned integer in the range 0...4294967295. When set to 0, the
kernel's default value is used. Defaults to 256.
Added in version 249.
NetLabel=
This applies the NetLabel for the addresses received with DHCP, like
NetLabel= in [Address] section applies it to statically configured
addresses. See NetLabel= in [Address] section for more details.
Added in version 252.
NFTSet=
This applies the NFT set for the network configuration received with
DHCP, like NFTSet= in [Address] section applies it to static
configuration. See NFTSet= in [Address] section for more details.
For "address" or "prefix" source types, the type of the element used
in the NFT filter must be "ipv6_addr".
Added in version 255.
[IPV6ACCEPTRA] SECTION OPTIONS
The [IPv6AcceptRA] section configures the IPv6 Router Advertisement (RA)
client, if it is enabled with the IPv6AcceptRA= setting described above:
UseRedirect=
When true (the default), Redirect message sent by the current
first-hop router will be accepted, and routes to redirected nodes
will be configured.
Added in version 256.
Token=
Specifies an optional address generation mode for the Stateless
Address Autoconfiguration (SLAAC). The following values are
supported:
eui64
The EUI-64 algorithm will be used to generate an address for
that prefix. Only supported by Ethernet or InfiniBand
interfaces.
Added in version 250.
static:ADDRESS
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.
Added in version 250.
prefixstable[:ADDRESS][,UUID]
The algorithm specified in RFC 7217[37] will be used to generate
interface identifiers. 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.
This mode can also optionally take a non-null UUID in the format
which sd_id128_from_string() accepts, e.g.
"86b123b969ba4b7eb8b3d8605123525a" or
"86b123b9-69ba-4b7e-b8b3-d8605123525a". If a UUID is specified,
the value is used as the secret key to generate interface
identifiers. If not specified, then an application specific ID
generated with the system's machine-ID will be used as the
secret key. See sd-id128(3), sd_id128_from_string(3), and
sd_id128_get_machine(3).
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 be changed,
even if the prefix received in the RA message has not been
changed.
Added in version 250.
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 for
Ethernet or InfiniBand interfaces, otherwise "prefixstable" will be
used to form an interface identifier for that prefix.
This setting can be specified multiple times. If an empty string is
assigned, then the all previous assignments are cleared.
Examples:
Token=eui64
Token=::1a:2b:3c:4d
Token=static:::1a:2b:3c:4d
Token=prefixstable
Token=prefixstable:2002:da8:1::
Added in version 250.
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).
Added in version 231.
UseDNR=
When true, the DNR servers received in the Router Advertisement will
be used. Defaults to the value of UseDNS=.
Added in version 257.
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, similarly 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, similarly to the effect of the Domains= setting when the
argument is prefixed with "~". Defaults to false.
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).
Added in version 231.
RouteTable=num
The table identifier for the routes received in the Router
Advertisement. Takes one of predefined names "default", "main", and
"local", and names defined in RouteTable= in networkd.conf(5), or a
number between 1...4294967295.
When used in combination with VRF=, the VRF's routing table is used
when this parameter is not specified.
Added in version 232.
RouteMetric=
Set the routing metric for the routes received in the Router
Advertisement. Takes an unsigned integer in the range
0...4294967295, or three unsigned integer separated with ":", in
that case the first one is used when the router preference is high,
the second is for medium preference, and the last is for low
preference ("high:medium:low"). Defaults to "512:1024:2048".
Added in version 249.
QuickAck=
Takes a boolean. When true, the TCP quick ACK mode is enabled for
the routes configured by the received RAs. When unset, the kernel's
default will be used.
Added in version 253.
UseMTU=
Takes a boolean. When true, the MTU received in the Router
Advertisement will be used. Defaults to true.
Added in version 250.
UseHopLimit=
Takes a boolean. When true, the hop limit received in the Router
Advertisement will be set to routes configured based on the
advertisement. See also IPv6HopLimit=. Defaults to true.
Added in version 255.
UseReachableTime=
Takes a boolean. When true, the reachable time received in the
Router Advertisement will be set on the interface receiving the
advertisement. It is used as the base timespan of the validity of a
neighbor entry. Defaults to true.
Added in version 256.
UseRetransmissionTime=
Takes a boolean. When true, the retransmission time received in the
Router Advertisement will be set on the interface receiving the
advertisement. It is used as the time between retransmissions of
Neighbor Solicitation messages to a neighbor when resolving the
address or when probing the reachability of a neighbor. Defaults to
true.
Added in version 256.
UseGateway=
When true (the default), the router address will be configured as
the default gateway.
Added in version 250.
UseRoutePrefix=
When true (the default), the routes corresponding to the route
prefixes received in the Router Advertisement will be configured.
Added in version 250.
UseCaptivePortal=
When true (the default), the captive portal received in the Router
Advertisement will be recorded and made available to client programs
and displayed in the networkctl(1) status output per-link.
Added in version 254.
UsePREF64=
When true, the IPv6 PREF64 (or NAT64) prefixes received in the
Router Advertisement will be recorded and made available to client
programs and displayed in the networkctl(1) status output per-link.
See RFC 8781[38]. Defaults to false.
Added in version 255.
UseAutonomousPrefix=
When true (the default), the autonomous prefix received in the
Router Advertisement will be used and take precedence over any
statically configured ones.
Added in version 242.
UseOnLinkPrefix=
When true (the default), the onlink prefix received in the Router
Advertisement will be used and takes precedence over any statically
configured ones.
Added in version 242.
RouterDenyList=
A whitespace-separated list of IPv6 router addresses. Each address
can optionally take a prefix length after "/". Any information
advertised by the listed router is ignored.
Added in version 248.
RouterAllowList=
A whitespace-separated list of IPv6 router addresses. Each address
can optionally take a prefix length after "/". Only information
advertised by the listed router is accepted. Note that if
RouterAllowList= is configured then RouterDenyList= is ignored.
Added in version 248.
PrefixDenyList=
A whitespace-separated list of IPv6 prefixes. Each prefix can
optionally take its prefix length after "/". IPv6 prefixes supplied
via router advertisements in the list are ignored.
Added in version 248.
PrefixAllowList=
A whitespace-separated list of IPv6 prefixes. Each prefix can
optionally take its prefix length after "/". IPv6 prefixes supplied
via router advertisements in the list are allowed. Note that if
PrefixAllowList= is configured then PrefixDenyList= is ignored.
Added in version 248.
RouteDenyList=
A whitespace-separated list of IPv6 route prefixes. Each prefix can
optionally take its prefix length after "/". IPv6 route prefixes
supplied via router advertisements in the list are ignored.
Added in version 248.
RouteAllowList=
A whitespace-separated list of IPv6 route prefixes. Each prefix can
optionally take its prefix length after "/". IPv6 route prefixes
supplied via router advertisements in the list are allowed. Note
that if RouteAllowList= is configured then RouteDenyList= is
ignored.
Added in version 248.
DHCPv6Client=
Takes a boolean, or the special value "always". When true, the
DHCPv6 client will be started in "solicit" mode if the RA has the
"managed" flag or "information-request" mode if the RA lacks the
"managed" flag but has the "other configuration" flag. If set to
"always", the DHCPv6 client will be started in "solicit" mode when
an RA is received, even if neither the "managed" nor the "other
configuration" flag is set in the RA. This will be ignored when
WithoutRA= in the [DHCPv6] section is enabled, or
UplinkInterface=:self in the [DHCPPrefixDelegation] section is
specified. Defaults to true.
Added in version 246.
NetLabel=
This applies the NetLabel for the addresses received with RA, like
NetLabel= in [Address] section applies it to statically configured
addresses. See NetLabel= in [Address] section for more details.
Added in version 252.
NFTSet=
This applies the NFT set for the network configuration received with
RA, like NFTSet= in [Address] section applies it to static
configuration. See NFTSet= in [Address] section for more details.
For "address" or "prefix" source types, the type of the element used
in the NFT filter must be "ipv6_addr".
Added in version 255.
[DHCPSERVER] SECTION OPTIONS
The [DHCPServer] section contains settings for the DHCP server, if
enabled via the DHCPServer= option described above:
ServerAddress=
Specifies the server address for the DHCP server. Takes an IPv4
address with prefix length separated with a slash, e.g.
"192.168.0.1/24". Defaults to unset, and one of static IPv4
addresses configured in [Network] or [Address] section will be
automatically selected. This setting may be useful when the
interface on which the DHCP server is running has multiple static
IPv4 addresses.
This implies Address= in [Network] or [Address] section with the
same address and prefix length. That is,
[Network]
DHCPServer=yes
Address=192.168.0.1/24
Address=192.168.0.2/24
[DHCPServer]
ServerAddress=192.168.0.1/24
or
[Network]
DHCPServer=yes
[Address]
Address=192.168.0.1/24
[Address]
Address=192.168.0.2/24
[DHCPServer]
ServerAddress=192.168.0.1/24
are equivalent to the following:
[Network]
DHCPServer=yes
Address=192.168.0.2/24
[DHCPServer]
ServerAddress=192.168.0.1/24
Since version 255, like the Address= setting in [Network] or
[Address] section, this also supports a null address, e.g.
"0.0.0.0/24", and an unused address will be automatically selected.
For more details about the automatic address selection, see Address=
setting in [Network] section in the above.
Added in version 249.
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.
Added in version 226.
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.
Added in version 226.
UplinkInterface=
Specifies the name or the index of the uplink interface, or one of
the special values ":none" and ":auto". When emitting DNS, NTP, or
SIP servers is enabled but no servers are specified, the servers
configured in the uplink interface will be emitted. When ":auto",
the link which has a default gateway with the highest priority will
be automatically selected. When ":none", no uplink interface will be
selected. Defaults to ":auto".
Added in version 249.
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, or special value
"_server_address" which will be converted to the address used by the
DHCP server.
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.
This setting can be specified multiple times. If an empty string is
specified, then all DNS servers specified earlier are cleared.
Added in version 226.
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=.
Added in version 226.
EmitRouter=, Router=
The EmitRouter= setting takes a boolean value, and configures
whether the DHCP lease should contain the router option. The Router=
setting takes an IPv4 address, and configures the router address to
be emitted. When the Router= setting is not specified, then the
server address will be used for the router option. When the
EmitRouter= setting is disabled, the Router= setting will be
ignored. The EmitRouter= setting defaults to true, and the Router=
setting defaults to unset.
Added in version 230.
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.
Added in version 226.
BootServerAddress=
Takes an IPv4 address of the boot server used by e.g. PXE boot
systems. When specified, this address is sent in the siaddr field of
the DHCP message header. See RFC 2131[39] for more details. Defaults
to unset.
Added in version 251.
BootServerName=
Takes a name of the boot server used by e.g. PXE boot systems. When
specified, this name is sent in the DHCP option 66 ("TFTP server
name"). See RFC 2132[40] for more details. Defaults to unset.
Note that typically setting one of BootServerName= or
BootServerAddress= is sufficient, but both can be set too, if
desired.
Added in version 251.
BootFilename=
Takes a path or URL to a file loaded by e.g. a PXE boot loader. When
specified, this path is sent in the DHCP option 67 ("Bootfile
name"). See RFC 2132[40] for more details. Defaults to unset.
Added in version 251.
IPv6OnlyPreferredSec=
Takes a timespan. Controls the RFC 8925[33] IPv6-Only Preferred
option. Specifies the DHCPv4 option to indicate that a host supports
an IPv6-only mode and is willing to forgo obtaining an IPv4 address
if the network provides IPv6 connectivity. Defaults to unset, and
not send the option. The minimum allowed value is 300 seconds.
Added in version 255.
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[28]. This setting can be specified multiple times. If an
empty string is specified, then all options specified earlier are
cleared. Defaults to unset.
Added in version 244.
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[28]. This setting can be specified multiple times. If an
empty string is specified, then all options specified earlier are
cleared. Defaults to unset.
Added in version 246.
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 to "no".
Added in version 249.
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[41]. The address is the address of DHCP server or another
relay agent to forward DHCP messages to and from.
Added in version 249.
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.
Added in version 249.
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.
Added in version 249.
RapidCommit=
Takes a boolean. When true, the server supports RFC 4039[42]. When a
client sends a DHCPDISCOVER message with the Rapid Commit option to
the server, then the server will reply with a DHCPACK message to the
client, instead of DHCPOFFER. Defaults to true.
Added in version 255.
PersistLeases=
Takes a boolean. When true, the DHCP server will load and save
leases in the persistent storage. When false, the DHCP server will
neither load nor save leases in the persistent storage. Hence, bound
leases will be lost when the interface is reconfigured e.g. by
networkctl reconfigure, or systemd-networkd.service(8) is restarted.
That may cause address conflict on the network. So, please take an
extra care when disable this setting. When unspecified, the value
specified in the same setting in networkd.conf(5), which defaults to
"yes", will be used.
Added in version 256.
[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.
Added in version 249.
Address=
The IPv4 address that should be assigned to the device that was
matched with MACAddress=. This key is mandatory.
Added in version 249.
[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.
Added in version 235.
RouterLifetimeSec=
Takes a timespan. Configures the IPv6 router lifetime in seconds.
The value must be 0 seconds, or between 4 seconds and 9000 seconds.
When set to 0, the host is not acting as a router. Defaults to 1800
seconds (30 minutes).
Added in version 235.
ReachableTimeSec=
Configures the time, used in the Neighbor Unreachability Detection
algorithm, for which clients can assume a neighbor is reachable
after having received a reachability confirmation. Takes a time span
in the range 0...4294967295 ms. When 0, clients will handle it as if
the value was not specified. Defaults to 0.
Added in version 256.
RetransmitSec=
Configures the time, used in the Neighbor Unreachability Detection
algorithm, for which clients can use as retransmit time on address
resolution and the Neighbor Unreachability Detection algorithm.
Takes a time span in the range 0...4294967295 ms. When 0, clients
will handle it as if the value wasn't specified. Defaults to 0.
Added in version 255.
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[24] for details. Defaults to "medium".
Added in version 235.
HopLimit=
Configures hop limit. Takes an integer in the range 0...255. See
also IPv6HopLimit=.
Added in version 255.
UplinkInterface=
Specifies the name or the index of the uplink interface, or one of
the special values ":none" and ":auto". When emitting DNS servers or
search domains is enabled but no servers are specified, the servers
configured in the uplink interface will be emitted. When ":auto",
the value specified to the same setting in the
[DHCPPrefixDelegation] section will be used if DHCPPrefixDelegation=
is enabled, otherwise the link which has a default gateway with the
highest priority will be automatically selected. When ":none", no
uplink interface will be selected. Defaults to ":auto".
Added in version 250.
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 interface specified in UplinkInterface= will be used.
When EmitDNS= is false, no DNS server information is sent in Router
Advertisement messages. EmitDNS= defaults to true.
Added in version 235.
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 interface specified in UplinkInterface= will
be used. When EmitDomains= is false, no DNS search domain
information is sent in Router Advertisement messages. EmitDomains=
defaults to true.
Added in version 235.
DNSLifetimeSec=
Lifetime in seconds for the DNS server addresses listed in DNS= and
search domains listed in Domains=. Defaults to 3600 seconds (one
hour).
Added in version 235.
HomeAgent=
Takes a boolean. Specifies that IPv6 router advertisements indicate
to hosts that the router acts as a Home Agent and includes a Home
Agent option. Defaults to false. See RFC 6275[13] for further
details.
Added in version 255.
HomeAgentLifetimeSec=
Takes a timespan. Specifies the lifetime of the Home Agent. An
integer, the default unit is seconds, in the range 1...65535.
Defaults to the value set to RouterLifetimeSec=.
Added in version 255.
HomeAgentPreference=
Configures IPv6 Home Agent preference. Takes an integer in the range
0...65535. Defaults to 0.
Added in version 255.
[IPV6PREFIX] SECTION OPTIONS
One or more [IPv6Prefix] sections contain the IPv6 prefixes that are
announced via Router Advertisements. See RFC 4861[43] 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.
Added in version 235.
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.
Added in version 235.
PreferredLifetimeSec=, ValidLifetimeSec=
Preferred and valid lifetimes for the prefix measured in seconds.
PreferredLifetimeSec= defaults to 1800 seconds (30 minutes) and
ValidLifetimeSec= defaults to 3600 seconds (one hour).
Added in version 235.
Assign=
Takes a boolean. When true, adds an address from the prefix. Default
to false.
Added in version 246.
Token=
Specifies an optional address generation mode for assigning an
address in each prefix. This accepts the same syntax as Token= in
the [IPv6AcceptRA] section. If Assign= is set to false, then this
setting will be ignored. Defaults to unset, which means the EUI-64
algorithm will be used.
Added in version 250.
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.
Added in version 249.
[IPV6ROUTEPREFIX] SECTION OPTIONS
One or more [IPv6RoutePrefix] sections contain the IPv6 prefix routes
that are announced via Router Advertisements. See RFC 4191[24] 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 [IPv6RoutePrefix] sections to configure
multiple IPv6 prefix routes.
Added in version 244.
LifetimeSec=
Lifetime for the route prefix measured in seconds. LifetimeSec=
defaults to 3600 seconds (one hour).
Added in version 244.
[IPV6PREF64PREFIX] SECTION OPTIONS
One or more [IPv6PREF64Prefix] sections contain the IPv6 PREF64 (or
NAT64) prefixes that are announced via Router Advertisements. See RFC
8781[38] for further details.
Prefix=
The IPv6 PREF64 (or NAT64) prefix that is to be distributed to
hosts. The setting holds an IPv6 prefix that should be set up for
NAT64 translation (PLAT) to allow 464XLAT on the network segment.
Use multiple [IPv6PREF64Prefix] sections to configure multiple IPv6
prefixes since prefix lifetime may differ from one prefix to
another. The prefix is an address with a prefix length, separated by
a slash "/" character. Valid NAT64 prefix length are 96, 64, 56, 48,
40, and 32 bits.
Added in version 255.
LifetimeSec=
Lifetime for the prefix measured in seconds. Should be greater than
or equal to RouterLifetimeSec=. LifetimeSec= defaults to 1800
seconds.
Added in version 255.
[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.
Added in version 223.
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.
Added in version 242.
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.
Added in version 240.
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.
Added in version 242.
Learning=
Takes a boolean. Configures whether MAC address learning is enabled
for this port. When unset, the kernel's default will be used.
Added in version 242.
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.
Added in version 223.
Isolated=
Takes a boolean. Configures whether this port is isolated or not.
Within a bridge, isolated ports can only communicate with
non-isolated ports. When set to true, this port can only communicate
with other ports whose Isolated setting is false. When set to false,
this port can communicate with any other ports. When unset, the
kernel's default will be used.
Added in version 251.
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.
Added in version 223.
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.
Added in version 223.
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.
Added in version 223.
ProxyARP=
Takes a boolean. Configures whether proxy ARP to be enabled on this
port. When unset, the kernel's default will be used.
Added in version 243.
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.
Added in version 243.
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.
Added in version 243.
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.
Added in version 218.
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. systemd-networkd does not set any
default, meaning the kernel default value of 32 is used.
Added in version 234.
[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.
Added in version 219.
Destination=
Takes an IP address of the destination VXLAN tunnel endpoint.
Added in version 243.
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.
Added in version 219.
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.
Added in version 243.
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 is
valid if the referenced device is a VXLAN type device and has route
shortcircuit enabled. Defaults to "self".
Added in version 243.
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.
Added in version 249.
[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, IPv6, or L2 MAC multicast group address to add.
This setting is mandatory.
Added in version 247.
VLANId=
The VLAN ID for the new entry. Valid ranges are 0 (no VLAN) to 4094.
Optional, defaults to 0.
Added in version 247.
[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.
Added in version 246.
[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.
Added in version 239.
SamplePoint=
Optional sample point in percent with one decimal (e.g. "75%",
"87.5%") or permille (e.g. "875‰"). This will be ignored when
BitRate= is unspecified.
Added in version 239.
TimeQuantaNSec=, PropagationSegment=, PhaseBufferSegment1=,
PhaseBufferSegment2=, SyncJumpWidth=
Specifies the time quanta, propagation segment, phase buffer segment
1 and 2, and the synchronization jump width, which allow one to
define the CAN bit-timing in a hardware independent format as
proposed by the Bosch CAN 2.0 Specification. TimeQuantaNSec= takes
a timespan in nanoseconds. PropagationSegment=,
PhaseBufferSegment1=, PhaseBufferSegment2=, and SyncJumpWidth= take
number of time quantum specified in TimeQuantaNSec= and must be an
unsigned integer in the range 0...4294967295. These settings except
for SyncJumpWidth= will be ignored when BitRate= is specified.
Added in version 250.
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.
Added in version 246.
DataTimeQuantaNSec=, DataPropagationSegment=, DataPhaseBufferSegment1=,
DataPhaseBufferSegment2=, DataSyncJumpWidth=
Specifies the time quanta, propagation segment, phase buffer segment
1 and 2, and the synchronization jump width for the data phase, if
CAN-FD is used. These settings are analogous to the TimeQuantaNSec=
or related settings.
Added in version 250.
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, or DataTimeQuanta= and related settings.
Added in version 246.
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.
Added in version 246.
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.
Added in version 239.
Termination=
Takes a boolean or a termination resistor value in ohm in the range
0...65535. When "yes", the termination resistor is set to 120 ohm.
When "no" or "0" is set, the termination resistor is disabled. When
unset, the kernel's default will be used.
Added in version 246.
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.
Added in version 242.
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.
Added in version 248.
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.
Added in version 246.
Loopback=
Takes a boolean. When "yes", loopback mode is enabled. When the
loopback mode is enabled, the interface treats messages transmitted
by itself as received messages. The loopback mode is important to
debug CAN networks. When unset, the kernel's default will be used.
Added in version 250.
OneShot=
Takes a boolean. When "yes", one-shot mode is enabled. When unset,
the kernel's default will be used.
Added in version 250.
PresumeAck=
Takes a boolean. When "yes", the interface will ignore missing CAN
ACKs. When unset, the kernel's default will be used.
Added in version 250.
ClassicDataLengthCode=
Takes a boolean. When "yes", the interface will handle the 4bit data
length code (DLC). When unset, the kernel's default will be used.
Added in version 250.
[IPOIB] SECTION OPTIONS
The [IPoIB] section manages the IP over Infiniband and accepts the
following keys:
Mode=
Takes one of the special values "datagram" or "connected". Defaults
to unset, and the kernel's default is used.
When "datagram", the Infiniband unreliable datagram (UD) transport
is used, and so the interface MTU is equal to the IB L2 MTU minus
the IPoIB encapsulation header (4 bytes). For example, in a typical
IB fabric with a 2K MTU, the IPoIB MTU will be 2048 - 4 = 2044
bytes.
When "connected", the Infiniband reliable connected (RC) transport
is used. Connected mode takes advantage of the connected nature of
the IB transport and allows an MTU up to the maximal IP packet size
of 64K, which reduces the number of IP packets needed for handling
large UDP datagrams, TCP segments, etc and increases the performance
for large messages.
Added in version 250.
IgnoreUserspaceMulticastGroup=
Takes an boolean value. When true, the kernel ignores multicast
groups handled by userspace. Defaults to unset, and the kernel's
default is used.
Added in version 250.
[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.
Added in version 244.
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 0x1–0xffff 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.
Added in version 245.
DelayJitterSec=
Specifies the chosen delay to be added to the packets outgoing to
the network interface. Defaults to unset.
Added in version 245.
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.
Added in version 245.
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.
Added in version 245.
DuplicateRate=
Specifies that the chosen percent of packets is duplicated before
queuing them. Takes a percentage value, suffixed with "%". Defaults
to unset.
Added in version 245.
[TOKENBUCKETFILTER] SECTION OPTIONS
The [TokenBucketFilter] section manages the queueing discipline (qdisc)
of token bucket filter (tbf).
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 0x1–0xffff 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.
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.
Added in version 245.
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.
Added in version 246.
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.
Added in version 246.
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.
Added in version 245.
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.
Added in version 245.
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.
Added in version 245.
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.
Added in version 245.
[PIE] SECTION OPTIONS
The [PIE] section manages the queueing discipline (qdisc) of
Proportional Integral controller-Enhanced (PIE).
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 0x1–0xffff 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.
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.
Added in version 246.
[FLOWQUEUEPIE] SECTION OPTIONS
The "[FlowQueuePIE]" section manages the queueing discipline (qdisc) of
Flow Queue Proportional Integral controller-Enhanced (fq_pie).
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 0x1–0xffff 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.
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.
Added in version 247.
[STOCHASTICFAIRBLUE] SECTION OPTIONS
The [StochasticFairBlue] section manages the queueing discipline (qdisc)
of stochastic fair blue (sfb).
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 0x1–0xffff 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.
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.
Added in version 246.
[STOCHASTICFAIRNESSQUEUEING] SECTION OPTIONS
The [StochasticFairnessQueueing] section manages the queueing discipline
(qdisc) of stochastic fairness queueing (sfq).
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 0x1–0xffff 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.
PerturbPeriodSec=
Specifies the interval in seconds for queue algorithm perturbation.
Defaults to unset.
Added in version 245.
[BFIFO] SECTION OPTIONS
The [BFIFO] section manages the queueing discipline (qdisc) of Byte
limited Packet First In First Out (bfifo).
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 0x1–0xffff 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.
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.
Added in version 246.
[PFIFO] SECTION OPTIONS
The [PFIFO] section manages the queueing discipline (qdisc) of Packet
First In First Out (pfifo).
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 0x1–0xffff 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.
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.
Added in version 246.
[PFIFOHEADDROP] SECTION OPTIONS
The [PFIFOHeadDrop] section manages the queueing discipline (qdisc) of
Packet First In First Out Head Drop (pfifo_head_drop).
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 0x1–0xffff 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.
PacketLimit=
As in [PFIFO] section.
Added in version 246.
[PFIFOFAST] SECTION OPTIONS
The [PFIFOFast] section manages the queueing discipline (qdisc) of
Packet First In First Out Fast (pfifo_fast).
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 0x1–0xffff 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.
[CAKE] SECTION OPTIONS
The [CAKE] section manages the queueing discipline (qdisc) of Common
Applications Kept Enhanced (CAKE).
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 0x1–0xffff 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.
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.
Added in version 246.
AutoRateIngress=
Takes a boolean value. Enables automatic capacity estimation based
on traffic arriving at this qdisc. This is most likely to be useful
with cellular links, which tend to change quality randomly. If this
setting is enabled, the Bandwidth= setting is used as an initial
estimate. Defaults to unset, and the kernel's default is used.
Added in version 250.
OverheadBytes=
Specifies that bytes to be addeded to the size of each packet. Bytes
may be negative. Takes an integer in the range -64...256. Defaults
to unset and kernel's default is used.
Added in version 246.
MPUBytes=
Rounds each packet (including overhead) up to the specified bytes.
Takes an integer in the range 1...256. Defaults to unset and
kernel's default is used.
Added in version 250.
CompensationMode=
Takes one of "none", "atm", or "ptm". Specifies the compensation
mode for overhead calculation. When "none", no compensation is taken
into account. When "atm", enables the compensation for ATM cell
framing, which is normally found on ADSL links. When "ptm", enables
the compensation for PTM encoding, which is normally found on VDSL2
links and uses a 64b/65b encoding scheme. Defaults to unset and the
kernel's default is used.
Added in version 250.
UseRawPacketSize=
Takes a boolean value. When true, the packet size reported by the
Linux kernel will be used, instead of the underlying IP packet size.
Defaults to unset, and the kernel's default is used.
Added in version 250.
FlowIsolationMode=
CAKE places packets from different flows into different queues, then
packets from each queue are delivered fairly. This specifies whether
the fairness is based on source address, destination address,
individual flows, or any combination of those. The available values
are:
none
The flow isolation is disabled, and all traffic passes through a
single queue.
Added in version 250.
src-host
Flows are defined only by source address. Equivalent to the
"srchost" option for tc qdisc command. See also tc-cake(8).
Added in version 250.
dst-host
Flows are defined only by destination address. Equivalent to the
"dsthost" option for tc qdisc command. See also tc-cake(8).
Added in version 250.
hosts
Flows are defined by source-destination host pairs. Equivalent
to the same option for tc qdisc command. See also tc-cake(8).
Added in version 250.
flows
Flows are defined by the entire 5-tuple of source address,
destination address, transport protocol, source port and
destination port. Equivalent to the same option for tc qdisc
command. See also tc-cake(8).
Added in version 250.
dual-src-host
Flows are defined by the 5-tuple (see "flows" in the above), and
fairness is applied first over source addresses, then over
individual flows. Equivalent to the "dual-srchost" option for tc
qdisc command. See also tc-cake(8).
Added in version 250.
dual-dst-host
Flows are defined by the 5-tuple (see "flows" in the above), and
fairness is applied first over destination addresses, then over
individual flows. Equivalent to the "dual-dsthost" option for tc
qdisc command. See also tc-cake(8).
Added in version 250.
triple
Flows are defined by the 5-tuple (see "flows"), and fairness is
applied over source and destination addresses, and also over
individual flows. Equivalent to the "triple-isolate" option for
tc qdisc command. See also tc-cake(8).
Added in version 250.
Defaults to unset and the kernel's default is used.
Added in version 250.
NAT=
Takes a boolean value. When true, CAKE performs a NAT lookup before
applying flow-isolation rules, to determine the true addresses and
port numbers of the packet, to improve fairness between hosts inside
the NAT. This has no practical effect when FlowIsolationMode= is
"none" or "flows", or if NAT is performed on a different host.
Defaults to unset, and the kernel's default is used.
Added in version 250.
PriorityQueueingPreset=
CAKE divides traffic into "tins", and each tin has its own
independent set of flow-isolation queues, bandwidth threshold, and
priority. This specifies the preset of tin profiles. The available
values are:
besteffort
Disables priority queueing by placing all traffic in one tin.
Added in version 250.
precedence
Enables priority queueing based on the legacy interpretation of
TOS "Precedence" field. Use of this preset on the modern
Internet is firmly discouraged.
Added in version 250.
diffserv8
Enables priority queueing based on the Differentiated Service
("DiffServ") field with eight tins: Background Traffic, High
Throughput, Best Effort, Video Streaming, Low Latency
Transactions, Interactive Shell, Minimum Latency, and Network
Control.
Added in version 250.
diffserv4
Enables priority queueing based on the Differentiated Service
("DiffServ") field with four tins: Background Traffic, Best
Effort, Streaming Media, and Latency Sensitive.
Added in version 250.
diffserv3
Enables priority queueing based on the Differentiated Service
("DiffServ") field with three tins: Background Traffic, Best
Effort, and Latency Sensitive.
Added in version 250.
Defaults to unset, and the kernel's default is used.
Added in version 250.
FirewallMark=
Takes an integer in the range 1...4294967295. When specified,
firewall-mark-based overriding of CAKE's tin selection is enabled.
Defaults to unset, and the kernel's default is used.
Added in version 250.
Wash=
Takes a boolean value. When true, CAKE clears the DSCP fields,
except for ECN bits, of any packet passing through CAKE. Defaults to
unset, and the kernel's default is used.
Added in version 250.
SplitGSO=
Takes a boolean value. When true, CAKE will split General
Segmentation Offload (GSO) super-packets into their on-the-wire
components and dequeue them individually. Defaults to unset, and the
kernel's default is used.
Added in version 250.
RTTSec=
Specifies the RTT for the filter. Takes a timespan. Typical values
are e.g. 100us for extremely high-performance 10GigE+ networks like
datacentre, 1ms for non-WiFi LAN connections, 100ms for typical
internet connections. Defaults to unset, and the kernel's default
will be used.
Added in version 253.
AckFilter=
Takes a boolean value, or special value "aggressive". If enabled,
ACKs in each flow are queued and redundant ACKs to the upstream are
dropped. If yes, the filter will always keep at least two redundant
ACKs in the queue, while in "aggressive" mode, it will filter down
to a single ACK. This may improve download throughput on links with
very asymmetrical rate limits. Defaults to unset, and the kernel's
default will be used.
Added in version 253.
[CONTROLLEDDELAY] SECTION OPTIONS
The [ControlledDelay] section manages the queueing discipline (qdisc) of
controlled delay (CoDel).
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 0x1–0xffff 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.
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.
Added in version 245.
TargetSec=
Takes a timespan. Specifies the acceptable minimum
standing/persistent queue delay. Defaults to unset and kernel's
default is used.
Added in version 245.
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.
Added in version 245.
ECN=
Takes a boolean. This can be used to mark packets instead of
dropping them. Defaults to unset and kernel's default is used.
Added in version 245.
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.
Added in version 245.
[DEFICITROUNDROBINSCHEDULER] SECTION OPTIONS
The [DeficitRoundRobinScheduler] section manages the queueing discipline
(qdisc) of Deficit Round Robin Scheduler (DRR).
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 0x1–0xffff 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.
[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 0x1–0xffff
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 0x1–0xffff
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.
Added in version 246.
[ENHANCEDTRANSMISSIONSELECTION] SECTION OPTIONS
The [EnhancedTransmissionSelection] section manages the queueing
discipline (qdisc) of Enhanced Transmission Selection (ETS).
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 0x1–0xffff 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.
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=.
Added in version 246.
StrictBands=
Specifies the number of bands that should be created in strict mode.
An unsigned integer in the range 1...16.
Added in version 246.
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.
Added in version 246.
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.
Added in version 246.
[GENERICRANDOMEARLYDETECTION] SECTION OPTIONS
The [GenericRandomEarlyDetection] section manages the queueing
discipline (qdisc) of Generic Random Early Detection (GRED).
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 0x1–0xffff 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.
VirtualQueues=
Specifies the number of virtual queues. Takes an integer in the
range 1...16. Defaults to unset and kernel's default is used.
Added in version 246.
DefaultVirtualQueue=
Specifies the number of default virtual queue. This must be less
than VirtualQueue=. Defaults to unset and kernel's default is used.
Added in version 246.
GenericRIO=
Takes a boolean. It turns on the RIO-like buffering scheme. Defaults
to unset and kernel's default is used.
Added in version 246.
[FAIRQUEUEINGCONTROLLEDDELAY] SECTION OPTIONS
The [FairQueueingControlledDelay] section manages the queueing
discipline (qdisc) of fair queuing controlled delay (FQ-CoDel).
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 0x1–0xffff 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.
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.
Added in version 245.
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.
Added in version 246.
Flows=
Specifies the number of flows into which the incoming packets are
classified. Defaults to unset and kernel's default is used.
Added in version 245.
TargetSec=
Takes a timespan. Specifies the acceptable minimum
standing/persistent queue delay. Defaults to unset and kernel's
default is used.
Added in version 245.
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.
Added in version 245.
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.
Added in version 246.
ECN=
Takes a boolean. This can be used to mark packets instead of
dropping them. Defaults to unset and kernel's default is used.
Added in version 245.
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.
Added in version 245.
[FAIRQUEUEING] SECTION OPTIONS
The [FairQueueing] section manages the queueing discipline (qdisc) of
fair queue traffic policing (FQ).
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 0x1–0xffff 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.
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.
Added in version 245.
FlowLimit=
Specifies the hard limit on the maximum number of packets queued per
flow. Defaults to unset and kernel's default is used.
Added in version 245.
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.
Added in version 246.
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.
Added in version 245.
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.
Added in version 245.
Buckets=
Specifies the size of the hash table used for flow lookups. Defaults
to unset and kernel's default is used.
Added in version 245.
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.
Added in version 245.
Pacing=
Takes a boolean, and enables or disables flow pacing. Defaults to
unset and kernel's default is used.
Added in version 245.
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.
Added in version 245.
[TRIVIALLINKEQUALIZER] SECTION OPTIONS
The [TrivialLinkEqualizer] section manages the queueing discipline
(qdisc) of trivial link equalizer (teql).
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 0x1–0xffff 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.
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.
Added in version 245.
[HIERARCHYTOKENBUCKET] SECTION OPTIONS
The [HierarchyTokenBucket] section manages the queueing discipline
(qdisc) of hierarchy token bucket (htb).
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 0x1–0xffff 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.
DefaultClass=
Takes the minor id in hexadecimal of the default class. Unclassified
traffic gets sent to the class. Defaults to unset.
Added in version 246.
RateToQuantum=
Takes an unsigned integer. The DRR quantums are calculated by
dividing the value configured in Rate= by RateToQuantum=.
Added in version 246.
[HIERARCHYTOKENBUCKETCLASS] SECTION OPTIONS
The [HierarchyTokenBucketClass] section manages the traffic control
class of hierarchy token bucket (htb).
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 0x1–0xffff
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 0x1–0xffff
separated with a colon ("major:minor"). Defaults to unset.
Priority=
Specifies the priority of the class. In the round-robin process,
classes with the lowest priority field are tried for packets first.
Added in version 246.
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.
Added in version 246.
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.
Added in version 246.
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.
Added in version 246.
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.
Added in version 246.
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.
Added in version 246.
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.
Added in version 246.
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.
Added in version 246.
[CLASSFULMULTIQUEUEING] SECTION OPTIONS
The [ClassfulMultiQueueing] section manages the queueing discipline
(qdisc) of Classful Multi Queueing (mq).
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 0x1–0xffff 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.
[BANDMULTIQUEUEING] SECTION OPTIONS
The [BandMultiQueueing] section manages the queueing discipline (qdisc)
of Band Multi Queueing (multiq).
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 0x1–0xffff 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.
[HEAVYHITTERFILTER] SECTION OPTIONS
The [HeavyHitterFilter] section manages the queueing discipline (qdisc)
of Heavy Hitter Filter (hhf).
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 0x1–0xffff 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.
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.
Added in version 246.
[QUICKFAIRQUEUEING] SECTION OPTIONS
The [QuickFairQueueing] section manages the queueing discipline (qdisc)
of Quick Fair Queueing (QFQ).
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 0x1–0xffff 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.
[QUICKFAIRQUEUEINGCLASS] SECTION OPTIONS
The [QuickFairQueueingClass] section manages the traffic control class
of Quick Fair Queueing (qfq).
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 0x1–0xffff
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 0x1–0xffff
separated with a colon ("major:minor"). Defaults to unset.
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.
Added in version 246.
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.
Added in version 246.
[BRIDGEVLAN] SECTION OPTIONS
The [BridgeVLAN] section manages the VLAN ID configurations of a bridge
master or port, and accepts the following keys. To make the settings in
this section take an effect, VLANFiltering= option has to be enabled on
the bridge master, see the [Bridge] section in systemd.netdev(5). If at
least one valid settings specified in this section in a .network file
for an interface, all assigned VLAN IDs on the interface that are not
configured in the .network file will be removed. If VLAN IDs on an
interface need to be managed by other tools, then the settings in this
section cannot be used in the matching .network file.
VLAN=
The VLAN ID allowed on the port. This can be either a single ID or a
range M-N. Takes an integer in the range 1...4094. This setting can
be specified multiple times. If an empty string is assigned, then
the all previous assignments are cleared.
Added in version 231.
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. This setting can be specified multiple
times. If an empty string is assigned, then the all previous
assignments are cleared.
Added in version 231.
PVID=
The port VLAN ID specified here is assigned to all untagged frames
at ingress. Takes an VLAN ID or negative boolean value (e.g. "no").
When false, the currently assigned port VLAN ID will be dropped.
Configuring PVID= implicates the use of VLAN= setting in the above
and will enable the VLAN ID for ingress as well. Defaults to unset,
and will keep the assigned port VLAN ID if exists.
Added in version 231.
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 (DHCPv6 PD)
# /etc/systemd/network/55-dhcpv6-pd-upstream.network
[Match]
Name=enp1s0
[Network]
DHCP=ipv6
# The lines below are optional, to also assign an address in the delegated prefix
# to the upstream interface. Uncomment the lines below if necessary.
#[Network]
#DHCPPrefixDelegation=yes
#[DHCPPrefixDelegation]
#UplinkInterface=:self
#SubnetId=0
#Announce=no
# If the upstream network does not provides any Router Advertisement (RA) messages,
# then uncomment the lines below to make the DHCPv6 client forcibly started in the
# managed mode.
#[Network]
#IPv6AcceptRA=no
#[DHCPv6]
#WithoutRA=solicit
# If the upstream network provides Router Advertisement (RA) messages with the
# Managed bit unset, then uncomment the lines below to make the DHCPv6 client
# forcibly started in the managed mode when an RA is received.
#[DHCPv6]
#UseAddress=no
#[IPv6AcceptRA]
#DHCPv6Client=always
# /etc/systemd/network/55-dhcpv6-pd-downstream.network
[Match]
Name=enp2s0
[Network]
DHCPPrefixDelegation=yes
IPv6SendRA=yes
# It is expected that the host is acting as a router. So, usually it is not
# necessary to receive Router Advertisement from other hosts in the downstream network.
IPv6AcceptRA=no
[DHCPPrefixDelegation]
UplinkInterface=enp1s0
SubnetId=1
Announce=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. IPv6 Prefix Delegation (DHCPv4 6RD)
# /etc/systemd/network/55-dhcpv4-6rd-upstream.network
[Match]
Name=enp1s0
[Network]
DHCP=ipv4
# When DHCPv4-6RD is used, the upstream network does not support IPv6.
# Hence, it is not necessary to wait for Router Advertisement, which is enabled by default.
IPv6AcceptRA=no
[DHCPv4]
Use6RD=yes
# /etc/systemd/network/55-dhcpv4-6rd-downstream.network
[Match]
Name=enp2s0
[Network]
DHCPPrefixDelegation=yes
IPv6SendRA=yes
# It is expected that the host is acting as a router. So, usually it is not
# necessary to receive Router Advertisement from other hosts in the downstream network.
IPv6AcceptRA=no
[DHCPPrefixDelegation]
UplinkInterface=enp1s0
SubnetId=1
Announce=yes
This will enable DHCPv4-6RD on the interface enp1s0 as an upstream
interface where the DHCPv4 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 5. A bridge with two enslaved links
# /etc/systemd/network/25-bridge-static.netdev
[NetDev]
Name=bridge0
Kind=bridge
# /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 6. 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=100-299
[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 7. 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 8. 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 9. 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 will
not 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 10. MacVTap
This brings up a network interface "macvtap-test" and attaches it to
"enp0s25".
# /usr/lib/systemd/network/25-macvtap.network
[Match]
Name=enp0s25
[Network]
MACVTAP=macvtap-test
Example 11. 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-network-generator.service(8), systemd-
resolved.service(8)
NOTES
1. 💣💥🧨💥💥💣 Please note that those configuration files must be available
at all times. If /usr/local/ is a separate partition, it may not be
available during early boot, and must not be used for configuration.
2. System and Service Credentials
https://systemd.io/CREDENTIALS
3. Link-Local Multicast Name Resolution
https://tools.ietf.org/html/rfc4795
4. Multicast DNS
https://tools.ietf.org/html/rfc6762
5. DNS-over-TLS
https://tools.ietf.org/html/rfc7858
6. DNSSEC
https://tools.ietf.org/html/rfc4033
7. IEEE 802.1AB-2016
https://standards.ieee.org/findstds/standard/802.1AB-2016.html
8. RFC 5227
https://tools.ietf.org/html/rfc5227
9. IP Sysctl
https://docs.kernel.org/networking/ip-sysctl.html
10. RFC 4941
https://tools.ietf.org/html/rfc4941
11. RFC 3704
https://tools.ietf.org/html/rfc1027
12. RFC 3069
https://tools.ietf.org/html/rfc3069
13. RFC 6275
https://tools.ietf.org/html/rfc6275
14. RFC 4862
https://tools.ietf.org/html/rfc4862
15. RFC 3041
https://tools.ietf.org/html/rfc3041
16. NetLabel
https://docs.kernel.org/netlabel/index.html
17. Linux Security Modules (LSMs)
https://en.wikipedia.org/wiki/Linux_Security_Modules
18. NetLabel Fallback Peer Labeling
https://github.com/SELinuxProject/selinux-notebook/blob/main/src/network_support.md
19. NFT
https://netfilter.org/projects/nftables/index.html
20. RFC 3484
https://tools.ietf.org/html/rfc3484
21. Type of Service
https://en.wikipedia.org/wiki/Type_of_service
22. Differentiated services
https://en.wikipedia.org/wiki/Differentiated_services
23. Virtual Routing and Forwarding (VRF)
https://docs.kernel.org/networking/vrf.html
24. RFC 4191
https://tools.ietf.org/html/rfc4191
25. RFC 8520
https://tools.ietf.org/html/rfc8520
26. RFC 4039
https://tools.ietf.org/html/rfc4039
27. RFC 7844
https://tools.ietf.org/html/rfc7844
28. C-style escapes
https://en.wikipedia.org/wiki/Escape_sequences_in_C#Table_of_escape_sequences
29. RFC 9463
https://datatracker.ietf.org/doc/html/rfc9463
30. RFC 3442
https://datatracker.ietf.org/doc/html/rfc3442
31. RFC 5969
https://tools.ietf.org/html/rfc5969
32. RFC 7084
https://datatracker.ietf.org/doc/html/rfc7084
33. RFC 8925
https://tools.ietf.org/html/rfc8925
34. RFC 3315
https://tools.ietf.org/html/rfc3315#section-17.2.1
35. RFC 8415
https://www.rfc-editor.org/rfc/rfc8415.html#section-6.3
36. RFC 4291
https://tools.ietf.org/html/rfc4291#section-2.5.4
37. RFC 7217
https://tools.ietf.org/html/rfc7217
38. RFC 8781
https://tools.ietf.org/html/rfc8781
39. RFC 2131
https://www.rfc-editor.org/rfc/rfc2131.html
40. RFC 2132
https://www.rfc-editor.org/rfc/rfc2132.html
41. RFC 1542
https://tools.ietf.org/html/rfc1542
42. RFC 4039
https://datatracker.ietf.org/doc/html/rfc4039
43. RFC 4861
https://tools.ietf.org/html/rfc4861
systemd 257.9 SYSTEMD.NETWORK(5)
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