Provided by: systemd_237-3ubuntu8_amd64 bug

NAME

       systemd.network - Network configuration

SYNOPSIS

       network.network

DESCRIPTION

       Network setup is performed by systemd-networkd(8).

       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 directory /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 in /lib. 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 netdev file wherever located.
       (Of course, since /run is temporary and /usr/lib is for vendors, it is
       unlikely drop-ins should be used in either of those places.)

       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 device if each of the entries in the
       "[Match]" section matches, or if the section is empty. The following
       keys are accepted:

       MACAddress=
           The hardware address of the interface (use full colon-delimited
           hexadecimal, e.g., 01:23:45:67:89:ab).

       Path=
           A whitespace-separated list of shell-style globs matching the
           persistent path, as exposed by the udev property "ID_PATH". If the
           list is prefixed with a "!", the test is inverted; i.e. it is true
           when "ID_PATH" does not match any item in the list.

       Driver=
           A whitespace-separated list of shell-style globs matching the
           driver currently bound to the device, as exposed by the udev
           property "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 the udev property "DEVTYPE". If the list
           is prefixed with a "!", the test is inverted.

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

       Host=
           Matches against the hostname or machine ID of the host. See
           "ConditionHost=" in systemd.unit(5) for details.

       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.

       KernelCommandLine=
           Checks whether a specific kernel command line option is set (or if
           prefixed with the exclamation mark unset). See
           "ConditionKernelCommandLine=" in systemd.unit(5) for details.

       KernelVersion=
           Checks whether the kernel version (as reported by uname -r) matches
           a certain expression (or if prefixed with the exclamation mark does
           not match it). See "ConditionKernelVersion=" in systemd.unit(5) for
           details.

       Architecture=
           Checks whether the system is running on a specific architecture.
           See "ConditionArchitecture=" in systemd.unit(5) for details.

[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=
           A boolean. Enables or disables the ARP (low-level Address
           Resolution Protocol) for this interface. Defaults to unset, which
           means that the kernel 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.

       Unmanaged=
           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=
           A boolean. 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. Defaults to "yes".

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

       DHCPServer=
           A boolean. Enables DHCPv4 server support. 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", or "ipv6". Defaults to "ipv6".

       IPv4LLRoute=
           A boolean. When true, sets up the route needed for non-IPv4LL hosts
           to communicate with IPv4LL-only hosts. Defaults to false.

       IPv6Token=
           An IPv6 address with the top 64 bits unset. When set, indicates the
           64-bit interface part of SLAAC IPv6 addresses for this link. Note
           that the token is only ever used for SLAAC, and not for DHCPv6
           addresses, even in the case DHCP is requested by router
           advertisement. By default, the token is autogenerated.

       LLMNR=
           A boolean or "resolve". When true, enables Link-Local Multicast
           Name Resolution[1] 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=
           A boolean or "resolve". When true, enables Multicast DNS[2] 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).

       DNSSEC=
           A boolean or "allow-downgrade". When true, enables DNSSEC[3] 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-2009[4]. Note that configuring
           this setting to true is equivalent to "nearest-bridge", the
           recommended and most restricted level of propagation. See LLDP=
           above for an option to enable LLDP reception.

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

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

           If the specified address is 0.0.0.0 (for IPv4) or [::] (for IPv6),
           a new address range of the requested size is automatically
           allocated from a system-wide pool of unused ranges. 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 fc00::/7 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 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.

       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 either a
           boolean argument, 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[5] 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[6], 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=
           Enable or disable IPv6 Router Advertisement (RA) reception support
           for the interface. Takes a boolean parameter. If true, RAs are
           accepted; if false, RAs are ignored, independently of the local
           forwarding state. When not set, the kernel default is used, and RAs
           are accepted only when local forwarding is disabled for that
           interface. 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.

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

           Also see ip-sysctl.txt[5] 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.

       IPv6DuplicateAddressDetection=
           Configures the amount of IPv6 Duplicate Address Detection (DAD)
           probes to send. Defaults to unset.

       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. Defaults to unset.

       IPv4ProxyARP=
           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[7]. Defaults to unset.

       IPv6ProxyNDP=
           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. Defautls to
           unset.

       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=true but has no effect if IPv6ProxyNDP has been set to
           false. Defaults to unset.

       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.

       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.

       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.

       ActiveSlave=
           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=
           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=
           A boolean. Allows networkd to configure a specific link even if it
           has no carrier. Defaults to false.

[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.

       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 argument. Designates this address the "home
           address" as defined in RFC 6275[8]. Supported only on IPv6.
           Defaults to false.

       DuplicateAddressDetection=
           Takes a boolean argument. Do not perform Duplicate Address
           Detection RFC 4862[9] when adding this address. Supported only on
           IPv6. Defaults to false.

       ManageTemporaryAddress=
           Takes a boolean argument. If true the kernel manage temporary
           addresses created from this one as template on behalf of Privacy
           Extensions RFC 3041[10]. 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 to use privacy extensions in a manually configured
           network, just like if stateless auto-configuration was active.
           Defaults to false.

       PrefixRoute=
           Takes a boolean argument. When adding or modifying an IPv6 address,
           the userspace application needs a way to suppress adding a prefix
           route. This is for example relevant together with
           IFA_F_MANAGERTEMPADDR, where userspace creates autoconf generated
           addresses, but depending on on-link, no route for the prefix should
           be added. Defaults to false.

       AutoJoin=
           Takes a boolean argument. 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".

[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[11]. 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. The table identifier for a route (a number
           between 1 and 4294967295).

       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.

[ROUTE] SECTION OPTIONS

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

       Gateway=
           As in the "[Network]" section.

       GatewayOnlink=
           The "GatewayOnlink" option tells the kernel that it 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. A boolean,
           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[12] 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", "link" or "host".
           Defaults to "global".

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

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

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

       Type=
           The Type identifier for special route types, which can be "unicast"
           route to a destination network address which describes the path to
           the destination, "blackhole" packets are discarded silently,
           "unreachable" packets are discarded and the ICMP message host
           unreachable is generated, "prohibit" packets are discarded and the
           ICMP message communication administratively prohibited is
           generated. 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. Defaults to unset.

       InitialAdvertisedReceiveWindow=
           The TCP initial advertised receive window is the amount of receive
           data (in bytes) that can initally 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. Defaults to unset.

       QuickAck=
           Takes a boolean argument. When true enables TCP quick ack mode for
           the route. Defaults to unset.

[DHCP] SECTION OPTIONS

       The "[DHCP]" section configures the DHCPv4 and DHCP6 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).

       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.

       UseMTU=
           When true, the interface maximum transmission unit from the DHCP
           server will be used on the current link. Defaults to false.

       Anonymize=
           Takes a boolean argument. When true, the options sent to the DHCP
           server will follow the RFC 7844[13] (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=, SendHostname=, UseMTU=,
           VendorClassIdentifier=, UseTimezone=.

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

       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.

       UseDomains=
           Takes a boolean argument, 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".

       UseTimezone=
           When true, the timezone received from the DHCP server will be set
           as timezone of the local system. Defaults to "no".

       CriticalConnection=
           When true, the connection will never be torn down even if the DHCP
           lease expires. This is contrary to the DHCP specification, but may
           be the best choice if, say, the root filesystem relies on this
           connection. Defaults to false.

       ClientIdentifier=
           The DHCPv4 client identifier to use. Either "mac" to use the MAC
           address of the link or "duid" (the default, see below) to use an
           RFC4361-compliant Client ID.

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

       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.

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

       RapidCommit=
           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[14] for
           details. Defaults to true.

[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 argument, 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.

[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=
           Configures whether the DHCP leases handed out to clients shall
           contain DNS server information. The EmitDNS= setting takes a
           boolean argument and 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=.

       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=
           Configures whether the DHCP leases handed out to clients shall
           contain timezone information. The EmitTimezone= setting takes a
           boolean argument and 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.

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

       RouterLifetimeSec=
           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. Defaults to unset, which means 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[12] for details. Defaults to
           "medium".

       EmitDNS=, DNS=
           DNS= specifies a list of recursive DNS server IPv6 addresses that
           distributed via Router Advertisement messages when EmitDNS= is
           true. 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[15] for further
       details.

       AddressAutoconfiguration=, OnLink=
           Boolean values 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).

[BRIDGE] SECTION OPTIONS

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

       UnicastFlood=
           A boolean. Controls whether the bridge should flood traffic for
           which an FDB entry is missing and the destination is unknown
           through this port. Defaults to on.

       HairPin=
           A boolean. Configures whether traffic may be sent back out of the
           port on which it was received. By default, this flag is false, and
           the bridge will not forward traffic back out of the receiving port.

       UseBPDU=
           A boolean. Configures whether STP Bridge Protocol Data Units will
           be processed by the bridge port. Defaults to yes.

       FastLeave=
           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. Defaults
           to off.

       AllowPortToBeRoot=
           A boolean. Configures whether a given port is allowed to become a
           root port. Only used when STP is enabled on the bridge. Defaults to
           on.

       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.

       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.

[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. 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 4.

           # /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 5. 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 6. 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 7. 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 8. 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

SEE ALSO

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

NOTES

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

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

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

        4. IEEE 802.1AB-2009
           http://standards.ieee.org/getieee802/download/802.1AB-2009.pdf

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

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

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

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

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

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

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

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

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

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

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