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 | [IPV6ACCEPTRA] SECTION OPTIONS | [DHCPSERVER] SECTION OPTIONS | [IPV6PREFIXDELEGATION] SECTION OPTIONS | [IPV6PREFIX] SECTION OPTIONS | [IPV6ROUTEPREFIX] SECTION OPTIONS | [BRIDGE] SECTION OPTIONS | [BRIDGEFDB] SECTION OPTIONS | [LLDP] SECTION OPTIONS | [CAN] SECTION OPTIONS | [QDISC] SECTION OPTIONS | [NETWORKEMULATOR] SECTION OPTIONS | [TOKENBUCKETFILTER] SECTION OPTIONS | [PIE] 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 parsed after the file itself is 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.

       Note that an interface without any static IPv6 addresses configured,
       and neither DHCPv6 nor IPv6LL enabled, shall be considered to have no
       IPv6 support. IPv6 will be automatically disabled for that interface
       by writing "1" to /proc/sys/net/ipv6/conf/ifname/disable_ipv6.

[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 status. If the list is
           prefixed with a "!", the test is inverted.

       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.

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

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

       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.
           An unsigned integer in the range 0—4294967294. 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 when running
           systemd-networkd-wait-online. When "no", the network is ignored
           when checking for 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".

[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", "ipv6", "fallback", or "ipv4-fallback". If
           "fallback" or "ipv4-fallback" is specified, then an IPv4
           link-local address is configured only when DHCPv4 fails. If
           "fallback", an IPv6 link-local address is always configured, and
           if "ipv4-fallback", the address is not configured. Note that, the
           fallback mechanism works only when DHCPv4 client is enabled, that
           is, it requires "DHCP=yes" or "DHCP=ipv4". If Bridge= is set,
           defaults to "no", and if not, defaults to "ipv6".

       IPv6LinkLocalAddressGenerationMode=
           Specifies how IPv6 link local address is generated. Takes one of
           "eui64", "none", "stable-privacy" and "random". When unset, the
           kernel's default will be used. Note that if LinkLocalAdressing=
           not configured as "ipv6" then IPv6LinkLocalAddressGenerationMode=
           is ignored.

       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

       IPv6Token=
           Specifies an optional address generation mode and a required IPv6
           address. If the mode is present, the two parts must be separated
           with a colon "mode:address". The address generation mode may be
           either prefixstable or static. If not specified, static is
           assumed.

           When the mode is set to static, or unspecified, the lower bits of
           the supplied address are combined with the upper bits of a prefix
           received in a Router Advertisement 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 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.

           When the mode is set to "prefixstable" the RFC 7217 algorithm for
           generating interface identifiers will be used, but only when a
           prefix received in an RA message matches the supplied address.
           See RFC 7217[1]. Prefix matching will be attempted against each
           prefixstable IPv6Token variable provided in the configuration; if
           a received prefix does not match any of the provided addresses,
           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 includes both the interface's name and MAC
           address in the hash used 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. Note that if multiple prefixstable
           IPv6Token variables are supplied with addresses that match a
           prefix received in an RA message, only the first one will be used
           to generate addresses.

       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.

       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. 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 a boolean argument. Implies
           IPForward=ipv4. Defaults to "no".

       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.

       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.

       IPv6PrefixDelegation=
           Whether to enable or disable Router Advertisement sending on a
           link. Allowed values are "static" which distributes prefixes as
           defined in the [IPv6PrefixDelegation] and any [IPv6Prefix]
           sections, "dhcpv6" which requests prefixes using a DHCPv6 client
           configured for another link and any values configured in the
           [IPv6PrefixDelegation] section while ignoring all static prefix
           configuration sections, "yes" which uses both static
           configuration and DHCPv6, and "false" which turns off IPv6 prefix
           delegation altogether. Defaults to "false". See the
           [IPv6PrefixDelegation] and the [IPv6Prefix] sections for more
           configuration options.

       IPv6PDSubnetId=
           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[10], section 2.5.4), in which case the allowed value is
           hexadecimal, from 0 to 0x7fffffffffffffff inclusive. This option
           is only effective when used together with IPv6PrefixDelegation=
           and the corresponding configuration on the upstream interface.

       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.

       Bridge=
           The name of the bridge to add the link to. See systemd.netdev(5).

       Bond=
           The name of the bond to add the link to. See systemd.netdev(5).

       VRF=
           The name of the VRF to add the link to. See systemd.netdev(5).

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

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

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

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

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

       MACsec=
           The name of a MACsec device to create 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.

       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=
           The broadcast address, which must be in the format described in
           inet_pton(3). This key only applies to IPv4 addresses. If it is
           not given, it is derived from the Address= key.

       Label=
           An address label.

       PreferredLifetime=
           Allows the default "preferred lifetime" of the address to be
           overridden. Only three settings are accepted: "forever" or
           "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", "link" or "host"
           or an unsigned integer in the range 0—255. Defaults to "global".

       HomeAddress=
           Takes a boolean. Designates this address the "home address" as
           defined in RFC 6275[11]. Supported only on IPv6. Defaults to
           false.

       DuplicateAddressDetection=
           Takes one of "ipv4", "ipv6", "both", "none". When "ipv4",
           performs IPv4 Duplicate Address Detection. See RFC 5224[12]. When
           "ipv6", performs IPv6 Duplicate Address Detection. See RFC
           4862[13]. 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[14]. 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[15]. 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).

       Table=
           Specifies the routing table identifier to lookup if the rule
           selector matches. Takes one of "default", "main", and "local", 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.

[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.

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

       Id=
           The id of the nexthop (an unsigned integer). If unspecified or
           '0' then automatically chosen by kernel.

[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 special value "_dhcp". If "_dhcp",
           then the gateway address provided by DHCP (or in the IPv6 case,
           provided by 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., the kernel does not need to check if the gateway is
           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 (an unsigned integer).

       IPv6Preference=
           Specifies the route preference as defined in RFC 4191[16] 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 route, which can be "global", "site", "link",
           "host", or "nowhere". 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".

       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 "default", "main",
           "local" 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 data bytes will be sent during the initial
           burst of data. Takes a size in bytes between 1 and 4294967295
           (2^32 - 1). The usual suffixes K, M, G are supported and are
           understood to the base of 1024. When unset, the kernel's default
           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 size in bytes between 1 and
           4294967295 (2^32 - 1). The usual suffixes K, M, G are supported
           and are understood to the base of 1024. 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.

       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.

[DHCPV4] SECTION OPTIONS         top

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

       UseDNS=
           When true (the default), the DNS servers received from the DHCP
           server will be used and take precedence over any statically
           configured ones.

           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 false.

       UseNTP=
           When true (the default), the NTP servers received from the DHCP
           server will be used by systemd-timesyncd.service and take
           precedence over any statically configured ones.

       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.

       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)).

           Note that this configuration will overwrite others. In concrete,
           the following variables will be ignored: SendHostname=,
           ClientIdentifier=, UseRoutes=, UseMTU=, VendorClassIdentifier=,
           UseTimezone=.

           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.

       SendHostname=
           When true (the default), the machine's hostname will be sent to
           the DHCP server. Note that the machine's 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 is set to true.

       MUDURL=
           When configured, the Manufacturer Usage Descriptions (MUD) URL
           will be sent to the DHCPv4 server. Takes an 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[18].

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

       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.

       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".

       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 "no".

       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.

       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, so the network will not be overloaded even if this
           number is high.

       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.

       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.

       RouteMetric=
           Set the routing metric for routes specified by the DHCP server.
           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.

       ListenPort=
           Allow setting custom port for the DHCP client to listen on.

       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.

       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[12]. Defaults to "unset".

       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.

       RequestOptions=
           When configured, allows to set arbitrary request options in the
           DHCPv4 request options list and will be sent to the DHCPV4
           server. 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[19]. 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[19]. This
           setting can be specified multiple times. If an empty string is
           specified, then all options specified earlier are cleared.
           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:

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

       RouteMetric=
           Set the routing metric for routes specified by the DHCP server.
           Defaults to 1024.

       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.

       MUDURL=
           When configured, the Manufacturer Usage Descriptions (MUD) URL
           will be sent to the DHCPV6 server. Takes an URL of length up to
           255 characters. A superficial verification that the string is a
           valid URL will be performed. DHCPv6 clients are intended to have
           at most one MUD URL associated with them. See RFC 8520[18].

       RequestOptions=
           When configured, allows to set arbitrary request options in the
           DHCPv6 request options list and will sent to the DHCPV6 server. A
           whitespace-separated list of integers in the range 1..254.
           Defaults to unset.

       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[19]. This
           setting can be specified multiple times. If an empty string is
           specified, then all options specified earlier are cleared.
           Defaults to unset.

       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[21], 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.

       AssignAcquiredDelegatedPrefixAddress=
           Takes a boolean. Specifies whether to add an address from the
           delegated prefixes which are received from the WAN interface by
           the IPv6PrefixDelegation=. When true (on LAN interfce), the
           EUI-64 algorithm will be used to form an interface identifier
           from the delegated prefixes. Defaults to true.

       AssignAcquiredDelegatedPrefixToken=
           Specifies an optional address generation mode for
           AssignAcquiredDelegatedPrefixAddress=. Takes an IPv6 address.
           When set, the lower bits of the supplied address are combined
           with the upper bits of a delegatad prefix received from the WAN
           interface by the IPv6PrefixDelegation= prefixes to form a
           complete address.

       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.

       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.

       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.

       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[19]. 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.

[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 and take precedence over any
           statically configured ones.

           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.

       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 take precedence over any
           statically configured ones.

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

       DHCPv6Client=
           Takes a boolean, or the special value "always". When true (the
           default), the DHCPv6 client will be started when the RA has the
           managed or other information flag. If set to "always", the DHCPv6
           client will be started even if there is no managed or other
           information flag in the RA.

[DHCPSERVER] SECTION OPTIONS         top

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

       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.

       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 uplinkg 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[19]. 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[19]. This setting can be specified multiple
           times. If an empty string is specified, then all options
           specified earlier are cleared. Defaults to unset.

[IPV6PREFIXDELEGATION] SECTION OPTIONS         top

       The [IPv6PrefixDelegation] section contains settings for sending IPv6
       Router Advertisements and whether to act as a router, if enabled via
       the IPv6PrefixDelegation= option described above. IPv6 network
       prefixes are defined with one or more [IPv6Prefix] 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.
           If set, this host also announces itself in Router Advertisements
           as an IPv6 router for the network link. When unset, the host is
           not acting as a router.

       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[16] 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[22] 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.

[IPV6ROUTEPREFIX] SECTION OPTIONS         top

       One or more [IPv6RoutePrefix] sections contain the IPv6 prefix routes
       that are announced via Router Advertisements. See RFC 4191[16] 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".

[LLDP] SECTION OPTIONS         top

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

       MUDURL=
           Controls support for Ethernet LLDP packet's Manufacturer Usage
           Description (MUD). 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 intent to author a context-specific access policy,
           so the device functions only within those parameters. Takes an
           URL of length up to 255 characters. A superficial verification
           that the string is a valid URL will be performed. See RFC
           8520[18] for details. The MUD URL received from the LLDP packets
           will be saved at the state files and can be read via
           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.

       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.

[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 on the FIFO size in bytes. The size
           limit (a buffer size) to prevent it from overflowing in case it
           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's 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 FIFO size in number of packets.
           The size limit (a buffer size) to prevent it from overflowing in
           case it 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=
           Configues 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 white-space 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 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=
           Configues 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=
           Configues 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]
           IPv6PrefixDelegation=dhcpv6

           [DHCPv6]
           AssignAcquiredDelegatedPrefixAddress=yes

       This will enable IPv6 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.

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

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

       12. RFC 5224
           https://tools.ietf.org/html/rfc5227

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

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

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

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

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

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

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

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

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

       22. 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 2020-07-14.  (At that
       time, the date of the most recent commit that was found in the repos‐
       itory was 2020-07-14.)  If you discover any rendering problems in
       this HTML version of the page, or you believe there is a better or
       more up-to-date source for the page, or you have corrections or
       improvements to the information in this COLOPHON (which is not part
       of the original manual page), send a mail to man-pages@man7.org

systemd 246                                               SYSTEMD.NETWORK(5)

Pages that refer to this page: networkctl(1)resolvconf(1)resolvectl(1)dnssec-trust-anchors.d(5)networkd.conf(5)networkd.conf.d(5)systemd.link(5)systemd.negative(5)systemd.netdev(5)systemd.positive(5)30-systemd-environment-d-generator(7)systemd.directives(7)systemd.index(7)systemd.syntax(7)systemd-networkd(8)systemd-networkd.service(8)systemd-network-generator(8)systemd-network-generator.service(8)systemd-resolved(8)systemd-resolved.service(8)systemd-timesyncd(8)systemd-timesyncd.service(8)