Provided by: systemd_245.4-4ubuntu3.23_amd64 bug

NAME

       systemd.network - Network configuration

SYNOPSIS

       network.network

DESCRIPTION

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

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

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

       Along with the network file foo.network, a "drop-in" directory foo.network.d/ may exist.
       All files with the suffix ".conf" from this directory will be 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
       /lib/systemd/network or /run/systemd/network directories. Drop-in files in /etc take
       precedence over those in /run which in turn take precedence over those in /lib. Drop-in
       files under any of these directories take precedence over the main network file wherever
       located.

       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

       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 one, in which case the lists are merged.
           If the empty string is assigned to this option, the list of BSSID defined prior to
           this 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

       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.

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

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

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

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

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

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

[NETWORK] SECTION OPTIONS

       The "[Network]" section accepts the following keys:

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

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

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

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

           See the "[DHCPv4]" or "[DHCPv6]" section 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".

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

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

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

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

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

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

       DNS=
           A DNS server address, which must be in the format described in inet_pton(3). This
           option may be specified more than once. 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 host names (host names containing no dots) to
           become fully qualified domain names (FQDNs). If a single-label host name 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 host names 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. 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 adressing 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.

       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.

       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.

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

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

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

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

[ADDRESS] SECTION OPTIONS

       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 ranges 0 to 255. Defaults to "global".

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

       DuplicateAddressDetection=
           Takes one of "ipv4", "ipv6", "both", "none". When "ipv4", performs IPv4 Duplicate
           Address Detection. See RFC 5224[11]. When "ipv6", performs IPv6 Duplicate Address
           Detection. See RFC 4862[12]. Defaults to "ipv6".

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

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

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

[NEIGHBOR] SECTION OPTIONS

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

       Address=
           The IP address of the neighbor.

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

[IPV6ADDRESSLABEL] SECTION OPTIONS

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

       Label=
           The label for the prefix (an unsigned integer) ranges 0 to 4294967294. 0xffffffff is
           reserved. This key is mandatory.

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

[ROUTINGPOLICYRULE] SECTION OPTIONS

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

       TypeOfService=
           Specifies the type of service to match a number between 0 to 255.

       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

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

       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

       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 RFC4191[15] for Router Discovery
           messages. Which can be one of "low" the route has a lowest priority, "medium" the
           route has a default priority or "high" the route has a highest priority.

       Scope=
           The scope of the 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

       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 and take precedence over any statically configured ones.

       UseSIP=
           When true (the default), the SIP servers received from the DHCP server will be saved
           at the state files and can be read via sd_network_link_get_sip_servers() function.

       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[16] (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.

       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 true on Ubuntu.

           It is recommended to enable this option only on trusted networks, as setting this
           affects resolution of all host names, 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.

       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 unless this
           parameter is 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.

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

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

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

       RequestOptions=
           A whitespace-separated list of integers in the range 1–254.

       SendOption=
           Send an arbitrary 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[17]. 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

       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.

       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-method 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[18] for details. Defaults to true.

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

       PrefixDelegationHint=
           Takes an IPv6 address with prefix length as Address= in the "[Network]" section.
           Specifies the DHCPv6 client for the requesting router to include a prefix-hint in the
           DHCPv6 solicitation. Prefix ranges 1-128. Defaults to unset.

[IPV6ACCEPTRA] SECTION OPTIONS

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

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

           It is recommended to enable this option only on trusted networks, as setting this
           affects resolution of all host names, 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.

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

[DHCPSERVER] SECTION OPTIONS

       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=
           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 or NTP server information at
           a later point. DNS server propagation does not take /etc/resolv.conf into account.
           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=
           Similar to the EmitDNS= and DNS= settings described above, these settings configure
           whether and what NTP server information shall be emitted as part of the DHCP lease.
           The same syntax, propagation semantics and defaults apply as for EmitDNS= and DNS=.

       EmitSIP=, SIP=
           Similar to the EmitDNS= and DNS= settings described above, these settings configure
           whether and what SIP server information 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", or "string". Special
           characters in the data string may be escaped using C-style escapes[17]. 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

       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[15] for details. Defaults to "medium".

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

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

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

[IPV6PREFIX] SECTION OPTIONS

       One or more "[IPv6Prefix]" sections contain the IPv6 prefixes that are announced via
       Router Advertisements. See RFC 4861[20] 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).

[IPV6ROUTEPREFIX] SECTION OPTIONS

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

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

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

[BRIDGE] SECTION OPTIONS

       The "[Bridge]" section accepts the following keys.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[BRIDGEFDB] SECTION OPTIONS

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

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

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

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

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

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

[CAN] SECTION OPTIONS

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

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

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

       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.

       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.

[QDISC] SECTION OPTIONS

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

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

       Handle=
           Specifies the major number of unique identifier of the qdisc, known as the handle.
           Takes a number in hexadecimal ranges 1 to ffff. Defaults to unset.

[NETWORKEMULATOR] SECTION OPTIONS

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

       Parent=
           Specifies the parent Queueing Discipline (qdisc). Takes one of "root", "clsact" or
           "ingress". Defaults to "root".

       Handle=
           Specifies the major number of unique identifier of the qdisc, known as the handle.
           Takes a number in hexadecimal ranges 1 to ffff. 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 ranges 0 to 4294967294. Defaults to 1000.

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

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

[TOKENBUCKETFILTER] SECTION OPTIONS

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

       Parent=
           Specifies the parent Queueing Discipline (qdisc). Takes one of "root", "clsact" or
           "ingress". Defaults to "root".

       Handle=
           Specifies the major number of unique identifier of the qdisc, known as the handle.
           Takes a number in hexadecimal ranges 1 to ffff. 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.

       LimitSize=
           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 1000. Defaults to unset.

       Burst=
           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 1000.
           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 1000. 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 1000. Defaults to unset.

[STOCHASTICFAIRNESSQUEUEING] SECTION OPTIONS

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

       Parent=
           Specifies the parent Queueing Discipline (qdisc). Takes one of "root", "clsact" or
           "ingress". Defaults to "root".

       Handle=
           Specifies the major number of unique identifier of the qdisc, known as the handle.
           Takes a number in hexadecimal ranges 1 to ffff. Defaults to unset.

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

[CONTROLLEDDELAY] SECTION OPTIONS

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

       Parent=
           Specifies the parent Queueing Discipline (qdisc). Takes one of "root", "clsact" or
           "ingress". Defaults to "root".

       Handle=
           Specifies the major number of unique identifier of the qdisc, known as the handle.
           Takes a number in hexadecimal ranges 1 to ffff. Defaults to unset.

       PacketLimit=
           Specifies the hard limit on the queue size in number of packets. When this limit is
           reached, incoming packets are dropped. An unsigned integer ranges 0 to 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.

[FAIRQUEUEINGCONTROLLEDDELAY] SECTION OPTIONS

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

       Parent=
           Specifies the parent Queueing Discipline (qdisc). Takes one of "root", "clsact" or
           "ingress". Defaults to "root".

       Handle=
           Specifies the major number of unique identifier of the qdisc, known as the handle.
           Takes a number in hexadecimal ranges 1 to ffff. 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.

       MemoryLimit=
           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.

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

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

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

[FAIRQUEUEING] SECTION OPTIONS

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

       Parent=
           Specifies the parent Queueing Discipline (qdisc). Takes one of "root", "clsact" or
           "ingress". Defaults to "root".

       Handle=
           Specifies the major number of unique identifier of the qdisc, known as the handle.
           Takes a number in hexadecimal ranges 1 to ffff. 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.

       Quantum=
           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.

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

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

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

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

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

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

[TRIVIALLINKEQUALIZER] SECTION OPTIONS

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

       Parent=
           Specifies the parent Queueing Discipline (qdisc). Takes one of "root", "clsact" or
           "ingress". Defaults to "root".

       Handle=
           Specifies the major number of unique identifier of the qdisc, known as the handle.
           Takes a number in hexadecimal ranges 1 to ffff. 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.

[BRIDGEVLAN] SECTION OPTIONS

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

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

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

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

EXAMPLES

       Example 1. Static network configuration

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

           [Network]
           Address=192.168.0.15/24
           Gateway=192.168.0.1

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

       Example 2. DHCP on ethernet links

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

           [Network]
           DHCP=yes

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

       Example 3. IPv6 Prefix Delegation

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

           [Network]
           DHCP=ipv6

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

           [Network]
           IPv6PrefixDelegation=dhcpv6

       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".

           # /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

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

NOTES

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

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

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

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

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

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

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

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

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

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

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

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

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

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

       15. RFC4191
           https://tools.ietf.org/html/rfc4191

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

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

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

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

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