systemd.network(5) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | [MATCH] SECTION OPTIONS | [LINK] SECTION OPTIONS | [SR-IOV] SECTION OPTIONS | [NETWORK] SECTION OPTIONS | [ADDRESS] SECTION OPTIONS | [NEIGHBOR] SECTION OPTIONS | [IPV6ADDRESSLABEL] SECTION OPTIONS | [ROUTINGPOLICYRULE] SECTION OPTIONS | [NEXTHOP] SECTION OPTIONS | [ROUTE] SECTION OPTIONS | [DHCPV4] SECTION OPTIONS | [DHCPV6] SECTION OPTIONS | [DHCPV6PREFIXDELEGATION] SECTION OPTIONS | [IPV6ACCEPTRA] SECTION OPTIONS | [DHCPSERVER] SECTION OPTIONS | [DHCPSERVERSTATICLEASE] SECTION OPTIONS | [IPV6SENDRA] SECTION OPTIONS | [IPV6PREFIX] SECTION OPTIONS | [IPV6ROUTEPREFIX] SECTION OPTIONS | [BRIDGE] SECTION OPTIONS | [BRIDGEFDB] SECTION OPTIONS | [BRIDGEMDB] SECTION OPTIONS | [LLDP] SECTION OPTIONS | [CAN] SECTION OPTIONS | [QDISC] SECTION OPTIONS | [NETWORKEMULATOR] SECTION OPTIONS | [TOKENBUCKETFILTER] SECTION OPTIONS | [PIE] SECTION OPTIONS | [FLOWQUEUEPIE] SECTION OPTIONS | [STOCHASTICFAIRBLUE] SECTION OPTIONS | [STOCHASTICFAIRNESSQUEUEING] SECTION OPTIONS | [BFIFO] SECTION OPTIONS | [PFIFO] SECTION OPTIONS | [PFIFOHEADDROP] SECTION OPTIONS | [PFIFOFAST] SECTION OPTIONS | [CAKE] SECTION OPTIONS | [CONTROLLEDDELAY] SECTION OPTIONS | [DEFICITROUNDROBINSCHEDULER] SECTION OPTIONS | [DEFICITROUNDROBINSCHEDULERCLASS] SECTION OPTIONS | [ENHANCEDTRANSMISSIONSELECTION] SECTION OPTIONS | [GENERICRANDOMEARLYDETECTION] SECTION OPTIONS | [FAIRQUEUEINGCONTROLLEDDELAY] SECTION OPTIONS | [FAIRQUEUEING] SECTION OPTIONS | [TRIVIALLINKEQUALIZER] SECTION OPTIONS | [HIERARCHYTOKENBUCKET] SECTION OPTIONS | [HIERARCHYTOKENBUCKETCLASS] SECTION OPTIONS | [HEAVYHITTERFILTER] SECTION OPTIONS | [QUICKFAIRQUEUEING] SECTION OPTIONS | [QUICKFAIRQUEUEINGCLASS] SECTION OPTIONS | [BRIDGEVLAN] SECTION OPTIONS | EXAMPLES | SEE ALSO | NOTES | COLOPHON

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

NAME         top

       systemd.network - Network configuration

SYNOPSIS         top

       network.network

DESCRIPTION         top

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

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

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

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

       In addition to /etc/systemd/network, drop-in ".d" directories can
       be placed in /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         top

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

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

           Name=*

       The following keys are accepted:

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

           Example:

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

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

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

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

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

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

           Example: if a .link file has the following:

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

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

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

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

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

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

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

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

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

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

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

[LINK] SECTION OPTIONS         top

       The [Link] section accepts the following keys:

       MACAddress=
           The hardware address to set for the device.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[SR-IOV] SECTION OPTIONS         top

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

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

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

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

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

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

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

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

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

       MACAddress=
           Specifies the MAC address for the virtual function.

[NETWORK] SECTION OPTIONS         top

       The [Network] section accepts the following keys:

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

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

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

           Furthermore, note that by default the domain name specified
           through DHCP 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.

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

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

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

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

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

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

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

               ip route add default dev veth99

           or,

               [Route]
               Gateway=0.0.0.0

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

               [Route]
               Gateway=0.0.0.0
               Table=1234

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

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

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

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

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

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

           Examples:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

       Xfrm=
           The name of the xfrm to create on the link. See
           systemd.netdev(5). This option may be specified more than
           once.

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

[ADDRESS] SECTION OPTIONS         top

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

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

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

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

       Label=
           An address label.

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

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

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

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

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

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

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

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

[NEIGHBOR] SECTION OPTIONS         top

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

       Address=
           The IP address of the neighbor.

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

[IPV6ADDRESSLABEL] SECTION OPTIONS         top

       An [IPv6AddressLabel] section accepts the following keys. Specify
       several [IPv6AddressLabel] sections to configure several address
       labels. IPv6 address labels are used for address selection. See
       RFC 3484[14]. Precedence is managed by userspace, and only the
       label itself is stored in the kernel.

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

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

[ROUTINGPOLICYRULE] SECTION OPTIONS         top

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

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

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

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

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

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

       Priority=
           Specifies the priority of this rule.  Priority= is an
           unsigned integer. Higher number means lower priority, and
           rules get processed in order of increasing number.

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

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

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

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

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

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

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

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

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

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

[NEXTHOP] SECTION OPTIONS         top

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

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

       Gateway=
           As in the [Network] section.

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

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

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

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

[ROUTE] SECTION OPTIONS         top

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

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

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

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

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

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

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

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

           •   "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 doesn't exist.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[DHCPV4] SECTION OPTIONS         top

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[DHCPV6] SECTION OPTIONS         top

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

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

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

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

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

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

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

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

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

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

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

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

[DHCPV6PREFIXDELEGATION] SECTION OPTIONS         top

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

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

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

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

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

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

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

[IPV6ACCEPTRA] SECTION OPTIONS         top

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[DHCPSERVER] SECTION OPTIONS         top

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

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

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

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

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

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

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

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

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

       SendOption=
           Send a raw option with value via DHCPv4 server. Takes a DHCP
           option number, data type and data ("option:type:value"). The
           option number is an integer in the range 1...254. The type
           takes one of "uint8", "uint16", "uint32", "ipv4address",
           "ipv6address", or "string". Special characters in the data
           string may be escaped using C-style escapes[18]. This setting
           can be specified multiple times. If an empty string is
           specified, then all options specified earlier are cleared.
           Defaults to unset.

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

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

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

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

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

[DHCPSERVERSTATICLEASE] SECTION OPTIONS         top

       The "[DHCPServerStaticLease]" section configures a static DHCP
       lease to assign a pre-set 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 which should be assigned
           IPv4 address specified in Address=. This key is mandatory.

       Address=
           IPv4 address that should be assigned to a device with a
           hardware address specified in MACAddress=. This key is
           mandatory.

[IPV6SENDRA] SECTION OPTIONS         top

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

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

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

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

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

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

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

[IPV6PREFIX] SECTION OPTIONS         top

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

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

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

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

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

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

[IPV6ROUTEPREFIX] SECTION OPTIONS         top

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

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

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

[BRIDGE] SECTION OPTIONS         top

       The [Bridge] section accepts the following keys:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[BRIDGEFDB] SECTION OPTIONS         top

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

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

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

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

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

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

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

[BRIDGEMDB] SECTION OPTIONS         top

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

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

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

[LLDP] SECTION OPTIONS         top

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

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

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

[CAN] SECTION OPTIONS         top

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

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

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

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

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

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

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

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

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

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

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

[QDISC] SECTION OPTIONS         top

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

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

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

[NETWORKEMULATOR] SECTION OPTIONS         top

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

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

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

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

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

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

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

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

[TOKENBUCKETFILTER] SECTION OPTIONS         top

       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–Oxffff separated with a colon
           ("major:minor"). Defaults to "root".

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

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

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

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

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

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

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

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

[PIE] SECTION OPTIONS         top

       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–Oxffff separated with a colon
           ("major:minor"). Defaults to "root".

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

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

[FLOWQUEUEPIE] SECTION OPTIONS         top

       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–Oxffff separated with a colon
           ("major:minor"). Defaults to "root".

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

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

[STOCHASTICFAIRBLUE] SECTION OPTIONS         top

       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–Oxffff separated with a colon
           ("major:minor"). Defaults to "root".

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

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

[STOCHASTICFAIRNESSQUEUEING] SECTION OPTIONS         top

       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–Oxffff separated with a colon
           ("major:minor"). Defaults to "root".

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

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

[BFIFO] SECTION OPTIONS         top

       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–Oxffff separated with a colon
           ("major:minor"). Defaults to "root".

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

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

[PFIFO] SECTION OPTIONS         top

       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–Oxffff separated with a colon
           ("major:minor"). Defaults to "root".

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

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

[PFIFOHEADDROP] SECTION OPTIONS         top

       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–Oxffff separated with a colon
           ("major:minor"). Defaults to "root".

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

       PacketLimit=
           As in [PFIFO] section.

[PFIFOFAST] SECTION OPTIONS         top

       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–Oxffff separated with a colon
           ("major:minor"). Defaults to "root".

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

[CAKE] SECTION OPTIONS         top

       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–Oxffff separated with a colon
           ("major:minor"). Defaults to "root".

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

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

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

[CONTROLLEDDELAY] SECTION OPTIONS         top

       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–Oxffff separated with a colon
           ("major:minor"). Defaults to "root".

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

       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.

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

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

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

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

[DEFICITROUNDROBINSCHEDULER] SECTION OPTIONS         top

       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–Oxffff separated with a colon
           ("major:minor"). Defaults to "root".

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

[DEFICITROUNDROBINSCHEDULERCLASS] SECTION OPTIONS         top

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

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

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

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

[ENHANCEDTRANSMISSIONSELECTION] SECTION OPTIONS         top

       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–Oxffff separated with a colon
           ("major:minor"). Defaults to "root".

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

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

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

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

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

[GENERICRANDOMEARLYDETECTION] SECTION OPTIONS         top

       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–Oxffff separated with a colon
           ("major:minor"). Defaults to "root".

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

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

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

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

[FAIRQUEUEINGCONTROLLEDDELAY] SECTION OPTIONS         top

       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–Oxffff separated with a colon
           ("major:minor"). Defaults to "root".

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

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

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

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

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

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

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

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

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

[FAIRQUEUEING] SECTION OPTIONS         top

       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–Oxffff separated with a colon
           ("major:minor"). Defaults to "root".

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

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

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

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

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

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

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

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

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

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

[TRIVIALLINKEQUALIZER] SECTION OPTIONS         top

       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–Oxffff separated with a colon
           ("major:minor"). Defaults to "root".

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

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

[HIERARCHYTOKENBUCKET] SECTION OPTIONS         top

       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–Oxffff separated with a colon
           ("major:minor"). Defaults to "root".

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

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

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

[HIERARCHYTOKENBUCKETCLASS] SECTION OPTIONS         top

       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–Oxffff separated with a colon ("major:minor").
           Defaults to "root".

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

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

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

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

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

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

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

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

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

[HEAVYHITTERFILTER] SECTION OPTIONS         top

       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–Oxffff separated with a colon
           ("major:minor"). Defaults to "root".

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

       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.

[QUICKFAIRQUEUEING] SECTION OPTIONS         top

       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–Oxffff separated with a colon
           ("major:minor"). Defaults to "root".

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

[QUICKFAIRQUEUEINGCLASS] SECTION OPTIONS         top

       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–Oxffff separated with a colon ("major:minor").
           Defaults to "root".

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

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

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

[BRIDGEVLAN] SECTION OPTIONS         top

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

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

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

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

EXAMPLES         top

       Example 1. Static network configuration

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

           [Network]
           Address=192.168.0.15/24
           Gateway=192.168.0.1

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

       Example 2. DHCP on ethernet links

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

           [Network]
           DHCP=yes

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

       Example 3. IPv6 Prefix Delegation

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

           [Network]
           DHCP=ipv6

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

           [Network]
           IPv6SendRA=yes
           DHCPv6PrefixDelegation=yes

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

       Example 4. A bridge with two enslaved links

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

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

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

           [Network]
           Bridge=bridge0

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

           [Network]
           Bridge=bridge0

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

       Example 5.

           # /etc/systemd/network/20-bridge-slave-interface-vlan.network
           [Match]
           Name=enp2s0

           [Network]
           Bridge=bridge0

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

           [BridgeVLAN]
           VLAN=100-200

           [BridgeVLAN]
           EgressUntagged=300-400

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

       Example 6. Various tunnels

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

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

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

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

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

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

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

       Example 7. A bond device

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

           [Network]
           DHCP=ipv6

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

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

           [Network]
           Bond=bond1

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

           [Network]
           Bond=bond1

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

       Example 8. Virtual Routing and Forwarding (VRF)

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

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

           [Network]
           VRF=vrf1

       Example 9. MacVTap

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

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

           [Network]
           MACVTAP=macvtap-test

       Example 10. A Xfrm interface with physical underlying device.

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

           [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         top

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

NOTES         top

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

COLOPHON         top

       This page is part of the systemd (systemd system and service
       manager) project.  Information about the project can be found at
       ⟨http://www.freedesktop.org/wiki/Software/systemd⟩.  If you have
       a bug report for this manual page, see
       ⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
       This page was obtained from the project's upstream Git repository
       ⟨https://github.com/systemd/systemd.git⟩ on 2021-06-20.  (At that
       time, the date of the most recent commit that was found in the
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systemd 249                                           SYSTEMD.NETWORK(5)

Pages that refer to this page: networkctl(1)resolvectl(1)dnssec-trust-anchors.d(5)networkd.conf(5)systemd.link(5)systemd.netdev(5)systemd.directives(7)systemd.index(7)systemd.syntax(7)systemd-networkd.service(8)systemd-network-generator.service(8)systemd-resolved.service(8)systemd-timesyncd.service(8)