man/systemd.network.xml

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  23
  24 <refentry id="systemd.network" conditional='ENABLE_NETWORKD'>
  25
  26   <refentryinfo>
  27     <title>systemd.network</title>
  28     <productname>systemd</productname>
  29
  30     <authorgroup>
  31       <author>
  32         <contrib>Developer</contrib>
  33         <firstname>Tom</firstname>
  34         <surname>Gundersen</surname>
  35         <email>teg@jklm.no</email>
  36       </author>
  37     </authorgroup>
  38   </refentryinfo>
  39
  40   <refmeta>
  41     <refentrytitle>systemd.network</refentrytitle>
  42     <manvolnum>5</manvolnum>
  43   </refmeta>
  44
  45   <refnamediv>
  46     <refname>systemd.network</refname>
  47     <refpurpose>Network configuration</refpurpose>
  48   </refnamediv>
  49
  50   <refsynopsisdiv>
  51     <para><filename><replaceable>network</replaceable>.network</filename></para>
  52   </refsynopsisdiv>
  53
  54   <refsect1>
  55     <title>Description</title>
  56
  57     <para>Network setup is performed by
  58     <citerefentry><refentrytitle>systemd-networkd</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
  59     </para>
  60
  61     <para>Network files must have the extension
  62     <filename>.network</filename>; other extensions are ignored.
  63     Networks are applied to links whenever the links appear.</para>
  64
  65     <para>The <filename>.network</filename> files are read from the
  66     files located in the system network directory
  67     <filename>/usr/lib/systemd/network</filename>, the volatile
  68     runtime network directory
  69     <filename>/run/systemd/network</filename> and the local
  70     administration network directory
  71     <filename>/etc/systemd/network</filename>. All configuration files
  72     are collectively sorted and processed in lexical order, regardless
  73     of the directories in which they live. However, files with
  74     identical filenames replace each other. Files in
  75     <filename>/etc</filename> have the highest priority, files in
  76     <filename>/run</filename> take precedence over files with the same
  77     name in <filename>/usr/lib</filename>. This can be used to
  78     override a system-supplied configuration file with a local file if
  79     needed. As a special case, an empty file (file size 0) or symlink
  80     with the same name pointing to <filename>/dev/null</filename>
  81     disables the configuration file entirely (it is "masked").</para>
  82   </refsect1>
  83
  84   <refsect1>
  85     <title>[Match] Section Options</title>
  86
  87       <para>The network file contains a <literal>[Match]</literal>
  88       section, which determines if a given network file may be applied
  89       to a given device; and a <literal>[Network]</literal> section
  90       specifying how the device should be configured. The first (in
  91       lexical order) of the network files that matches a given device
  92       is applied, all later files are ignored, even if they match as
  93       well.</para>
  94
  95       <para>A network file is said to match a device if each of the
  96       entries in the <literal>[Match]</literal> section matches, or if
  97       the section is empty. The following keys are accepted:</para>
  98
  99       <variablelist class='network-directives'>
 100         <varlistentry>
 101           <term><varname>MACAddress=</varname></term>
 102           <listitem>
 103             <para>The hardware address.</para>
 104           </listitem>
 105         </varlistentry>
 106         <varlistentry>
 107           <term><varname>Path=</varname></term>
 108           <listitem>
 109             <para>A whitespace-separated list of shell-style globs
 110             matching the persistent path, as exposed by the udev
 111             property <literal>ID_PATH</literal>.</para>
 112           </listitem>
 113         </varlistentry>
 114         <varlistentry>
 115           <term><varname>Driver=</varname></term>
 116           <listitem>
 117             <para>A whitespace-separated list of shell-style globs
 118             matching the driver currently bound to the device, as
 119             exposed by the udev property <literal>DRIVER</literal>
 120             of its parent device, or if that is not set the driver
 121             as exposed by <literal>ethtool -i</literal> of the
 122             device itself.</para>
 123           </listitem>
 124         </varlistentry>
 125         <varlistentry>
 126           <term><varname>Type=</varname></term>
 127           <listitem>
 128             <para>A whitespace-separated list of shell-style globs
 129             matching the device type, as exposed by the udev property
 130             <literal>DEVTYPE</literal>.</para>
 131           </listitem>
 132         </varlistentry>
 133         <varlistentry>
 134           <term><varname>Name=</varname></term>
 135           <listitem>
 136             <para>A whitespace-separated list of shell-style globs
 137             matching the device name, as exposed by the udev property
 138             <literal>INTERFACE</literal>.</para>
 139           </listitem>
 140         </varlistentry>
 141         <varlistentry>
 142           <term><varname>Host=</varname></term>
 143           <listitem>
 144             <para>Matches against the hostname or machine ID of the
 145             host. See <literal>ConditionHost=</literal> in
 146             <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 147             for details.
 148             </para>
 149           </listitem>
 150         </varlistentry>
 151         <varlistentry>
 152           <term><varname>Virtualization=</varname></term>
 153           <listitem>
 154             <para>Checks whether the system is executed in a virtualized
 155             environment and optionally test whether it is a specific
 156             implementation. See <literal>ConditionVirtualization=</literal> in
 157             <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 158             for details.
 159             </para>
 160           </listitem>
 161         </varlistentry>
 162         <varlistentry>
 163           <term><varname>KernelCommandLine=</varname></term>
 164           <listitem>
 165             <para>Checks whether a specific kernel command line option is
 166             set (or if prefixed with the exclamation mark unset). See
 167             <literal>ConditionKernelCommandLine=</literal> in
 168             <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 169             for details.
 170             </para>
 171           </listitem>
 172         </varlistentry>
 173         <varlistentry>
 174           <term><varname>Architecture=</varname></term>
 175           <listitem>
 176             <para>Checks whether the system is running on a specific
 177             architecture. See <literal>ConditionArchitecture=</literal> in
 178             <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 179             for details.
 180             </para>
 181           </listitem>
 182         </varlistentry>
 183       </variablelist>
 184
 185   </refsect1>
 186
 187   <refsect1>
 188     <title>[Link] Section Options</title>
 189
 190     <para> The <literal>[Link]</literal> section accepts the following keys:</para>
 191
 192     <variablelist class='network-directives'>
 193       <varlistentry>
 194         <term><varname>MACAddress=</varname></term>
 195         <listitem>
 196           <para>The hardware address.</para>
 197         </listitem>
 198       </varlistentry>
 199       <varlistentry>
 200         <term><varname>MTUBytes=</varname></term>
 201         <listitem>
 202           <para>The maximum transmission unit in bytes to set for the
 203           device. The usual suffixes K, M, G, are supported and are
 204           understood to the base of 1024.</para>
 205         </listitem>
 206       </varlistentry>
 207     </variablelist>
 208   </refsect1>
 209
 210   <refsect1>
 211     <title>[Network] Section Options</title>
 212
 213       <para>The <literal>[Network]</literal> section accepts the following keys:</para>
 214
 215       <variablelist class='network-directives'>
 216         <varlistentry>
 217           <term><varname>Description=</varname></term>
 218           <listitem>
 219             <para>A description of the device. This is only used for
 220             presentation purposes.</para>
 221           </listitem>
 222         </varlistentry>
 223         <varlistentry>
 224           <term><varname>DHCP=</varname></term>
 225           <listitem>
 226             <para>Enables DHCPv4 and/or DHCPv6 client support. Accepts
 227             <literal>yes</literal>, <literal>no</literal>,
 228             <literal>ipv4</literal>, or <literal>ipv6</literal>.</para>
 229
 230             <para>Note that DHCPv6 will by default be triggered by Router
 231             Advertisement, if that is enabled, regardless of this parameter.
 232             By enabling DHCPv6 support explicitly, the DHCPv6 client will
 233             be started regardless of the presence of routers on the link,
 234             or what flags the routers pass. See
 235             <literal>IPv6AcceptRouterAdvertisements=</literal>.</para>
 236
 237             <para>Furthermore, note that by default the domain name
 238             specified through DHCP is not used for name resolution.
 239             See option <option>UseDomains=</option> below.</para>
 240           </listitem>
 241         </varlistentry>
 242         <varlistentry>
 243           <term><varname>DHCPServer=</varname></term>
 244           <listitem>
 245             <para>A boolean. Enables DHCPv4 server support. Defaults
 246             to <literal>no</literal>. Further settings for the DHCP
 247             server may be set in the <literal>[DHCPServer]</literal>
 248             section described below.</para>
 249           </listitem>
 250         </varlistentry>
 251         <varlistentry>
 252           <term><varname>LinkLocalAddressing=</varname></term>
 253           <listitem>
 254             <para>Enables link-local address autoconfiguration. Accepts
 255             <literal>yes</literal>, <literal>no</literal>,
 256             <literal>ipv4</literal>, or <literal>ipv6</literal>. Defaults to
 257             <literal>ipv6</literal>.</para>
 258           </listitem>
 259         </varlistentry>
 260         <varlistentry>
 261           <term><varname>IPv4LLRoute=</varname></term>
 262           <listitem>
 263             <para>A boolean. When true, sets up the route needed for
 264             non-IPv4LL hosts to communicate with IPv4LL-only hosts. Defaults
 265             to false.
 266             </para>
 267           </listitem>
 268         </varlistentry>
 269         <varlistentry>
 270           <term><varname>IPv6Token=</varname></term>
 271           <listitem>
 272             <para>An IPv6 address with the top 64 bits unset. When set, indicates the
 273             64-bit interface part of SLAAC IPv6 addresses for this link. Note that
 274             the token is only ever used for SLAAC, and not for DHCPv6 addresses, even
 275             in the case DHCP is requested by router advertisement. By default, the
 276             token is autogenerated.</para>
 277           </listitem>
 278         </varlistentry>
 279         <varlistentry>
 280           <term><varname>LLMNR=</varname></term>
 281           <listitem>
 282             <para>A boolean or <literal>resolve</literal>. When true,
 283             enables <ulink
 284             url="https://tools.ietf.org/html/rfc4795">Link-Local
 285             Multicast Name Resolution</ulink> on the link. When set to
 286             <literal>resolve</literal>, only resolution is enabled,
 287             but not host registration and announcement. Defaults to
 288             true. This setting is read by
 289             <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 290           </listitem>
 291         </varlistentry>
 292         <varlistentry>
 293           <term><varname>MulticastDNS=</varname></term>
 294           <listitem>
 295             <para>A boolean or <literal>resolve</literal>. When true,
 296             enables <ulink
 297             url="https://tools.ietf.org/html/rfc6762">Multicast
 298             DNS</ulink> support on the link. When set to
 299             <literal>resolve</literal>, only resolution is enabled,
 300             but not host or service registration and
 301             announcement. Defaults to false. This setting is read by
 302             <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 303           </listitem>
 304         </varlistentry>
 305         <varlistentry>
 306           <term><varname>DNSSEC=</varname></term>
 307           <listitem>
 308             <para>A boolean or
 309             <literal>allow-downgrade</literal>. When true, enables
 310             <ulink
 311             url="https://tools.ietf.org/html/rfc4033">DNSSEC</ulink>
 312             DNS validation support on the link. When set to
 313             <literal>allow-downgrade</literal>, compatibility with
 314             non-DNSSEC capable networks is increased, by automatically
 315             turning off DNSEC in this case. This option defines a
 316             per-interface setting for
 317             <citerefentry><refentrytitle>resolved.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>'s
 318             global <varname>DNSSEC=</varname> option. Defaults to
 319             false. This setting is read by
 320             <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 321           </listitem>
 322         </varlistentry>
 323         <varlistentry>
 324           <term><varname>DNSSECNegativeTrustAnchors=</varname></term>
 325           <listitem><para>A space-separated list of DNSSEC negative
 326           trust anchor domains. If specified and DNSSEC is enabled,
 327           look-ups done via the interface's DNS server will be subject
 328           to the list of negative trust anchors, and not require
 329           authentication for the specified domains, or anything below
 330           it. Use this to disable DNSSEC authentication for specific
 331           private domains, that cannot be proven valid using the
 332           Internet DNS hierarchy. Defaults to the empty list. This
 333           setting is read by
 334           <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 335           </listitem>
 336         </varlistentry>
 337         <varlistentry>
 338           <term><varname>LLDP=</varname></term>
 339           <listitem>
 340             <para>Controls support for Ethernet LLDP packet reception. LLDP is a link-layer protocol commonly
 341             implemented on professional routers and bridges which announces which physical port a system is connected
 342             to, as well as other related data. Accepts a boolean or the special value
 343             <literal>routers-only</literal>. When true, incoming LLDP packets are accepted and a database of all LLDP
 344             neighbors maintained. If <literal>routers-only</literal> is set only LLDP data of various types of routers
 345             is collected and LLDP data about other types of devices ignored (such as stations, telephones and
 346             others). If false, LLDP reception is disabled. Defaults to <literal>routers-only</literal>. Use
 347             <citerefentry><refentrytitle>networkctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> to query the
 348             collected neighbor data. LLDP is only available on Ethernet links. See <varname>EmitLLDP=</varname> below
 349             for enabling LLDP packet emission from the local system.
 350             </para>
 351           </listitem>
 352         </varlistentry>
 353         <varlistentry>
 354           <term><varname>EmitLLDP=</varname></term>
 355           <listitem>
 356             <para>Controls support for Ethernet LLDP packet emission. Accepts a boolean parameter and defaults to
 357             false. If enabled a short LLDP packet with information about the local system is sent out in regular
 358             intervals on the link. The LLDP packet will contain information about the local host name, the local
 359             machine ID (as stored in
 360             <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>) and the
 361             local interface name, as well as the pretty hostname of the system (as set in
 362             <citerefentry><refentrytitle>machine-info</refentrytitle><manvolnum>5</manvolnum></citerefentry>). LLDP
 363             emission is only available on Ethernet links. Note that this setting passed data suitable for
 364             identification of host to the network and should thus not be used on untrusted networks, where such
 365             identification data should not be made available. Use this option to enable other systems to identify on
 366             which interface they are connected to this system. See <varname>LLDP=</varname> above for an option to
 367             enable LLDP reception.</para>
 368           </listitem>
 369         </varlistentry>
 370         <varlistentry>
 371           <term><varname>BindCarrier=</varname></term>
 372           <listitem>
 373             <para>A link name or a list of link names. When set, controls the behavior of the current
 374             link. When all links in the list are in an operational down state, the current link is brought
 375             down. When at least one link has carrier, the current interface is brought up.
 376             </para>
 377           </listitem>
 378         </varlistentry>
 379         <varlistentry>
 380           <term><varname>Address=</varname></term>
 381           <listitem>
 382             <para>A static IPv4 or IPv6 address and its prefix length,
 383             separated by a <literal>/</literal> character. Specify
 384             this key more than once to configure several addresses.
 385             The format of the address must be as described in
 386             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 387             This is a short-hand for an [Address] section only
 388             containing an Address key (see below). This option may be
 389             specified more than once.
 390             </para>
 391
 392             <para>If the specified address is 0.0.0.0 (for IPv4) or
 393             [::] (for IPv6), a new address range of the requested size
 394             is automatically allocated from a system-wide pool of
 395             unused ranges. The allocated range is checked against all
 396             current network interfaces and all known network
 397             configuration files to avoid address range conflicts. The
 398             default system-wide pool consists of 192.168.0.0/16,
 399             172.16.0.0/12 and 10.0.0.0/8 for IPv4, and fc00::/7 for
 400             IPv6. This functionality is useful to manage a large
 401             number of dynamically created network interfaces with the
 402             same network configuration and automatic address range
 403             assignment.</para>
 404
 405           </listitem>
 406         </varlistentry>
 407         <varlistentry>
 408           <term><varname>Gateway=</varname></term>
 409           <listitem>
 410             <para>The gateway address, which must be in the format
 411             described in
 412             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 413             This is a short-hand for a [Route] section only containing
 414             a Gateway key. This option may be specified more than
 415             once.</para>
 416           </listitem>
 417         </varlistentry>
 418         <varlistentry>
 419           <term><varname>DNS=</varname></term>
 420           <listitem>
 421             <para>A DNS server address, which must be in the format
 422             described in
 423             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 424             This option may be specified more than once. This setting is read by
 425             <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 426           </listitem>
 427         </varlistentry>
 428         <varlistentry>
 429           <term><varname>Domains=</varname></term>
 430           <listitem>
 431             <para>The domains used for DNS host name resolution on this link. Takes a list of DNS domain names which
 432             are used as search suffixes for extending single-label host names (host names containing no dots) to become
 433             fully qualified domain names (FQDNs). If a single-label host name is resolved on this interface, each of
 434             the specified search domains are appended to it in turn, converting it into a fully qualified domain name,
 435             until one of them may be successfully resolved.</para>
 436
 437             <para>The specified domains are also used for routing of DNS queries: look-ups for host names ending in the
 438             domains specified here are preferably routed to the DNS servers configured for this interface. If a domain
 439             name is prefixed with <literal>~</literal>, the domain name becomes a pure "routing" domain, is used for
 440             DNS query routing purposes only and is not used in the described domain search logic. By specifying a
 441             routing domain of <literal>~.</literal> (the tilde indicating definition of a routing domain, the dot
 442             referring to the DNS root domain which is the implied suffix of all valid DNS names) it is possible to
 443             route all DNS traffic preferably to the DNS server specified for this interface. The route domain logic is
 444             particularly useful on multi-homed hosts with DNS servers serving particular private DNS zones on each
 445             interface.</para>
 446
 447             <para>This setting is read by
 448             <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 449           </listitem>
 450         </varlistentry>
 451         <varlistentry>
 452           <term><varname>NTP=</varname></term>
 453           <listitem>
 454             <para>An NTP server address. This option may be specified more than once. This setting is read by
 455             <citerefentry><refentrytitle>systemd-timesyncd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 456           </listitem>
 457         </varlistentry>
 458         <varlistentry>
 459           <term><varname>IPForward=</varname></term>
 460           <listitem><para>Configures IP packet forwarding for the
 461           system. If enabled, incoming packets on any network
 462           interface will be forwarded to any other interfaces
 463           according to the routing table. Takes either a boolean
 464           argument, or the values <literal>ipv4</literal> or
 465           <literal>ipv6</literal>, which only enable IP packet
 466           forwarding for the specified address family.  This controls
 467           the <filename>net.ipv4.ip_forward</filename> and
 468           <filename>net.ipv6.conf.all.forwarding</filename> sysctl
 469           options of the network interface (see <ulink
 470           url="https://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt">ip-sysctl.txt</ulink>
 471           for details about sysctl options). Defaults to
 472           <literal>no</literal>.</para>
 473
 474           <para>Note: this setting controls a global kernel option,
 475           and does so one way only: if a network that has this setting
 476           enabled is set up the global setting is turned on.  However,
 477           it is never turned off again, even after all networks with
 478           this setting enabled are shut down again.</para>
 479
 480           <para>To allow IP packet forwarding only between specific
 481           network interfaces use a firewall.</para>
 482           </listitem>
 483         </varlistentry>
 484         <varlistentry>
 485           <term><varname>IPMasquerade=</varname></term>
 486           <listitem><para>Configures IP masquerading for the network
 487           interface. If enabled, packets forwarded from the network
 488           interface will be appear as coming from the local host.
 489           Takes a boolean argument. Implies
 490           <varname>IPForward=ipv4</varname>. Defaults to
 491           <literal>no</literal>.</para></listitem>
 492         </varlistentry>
 493         <varlistentry>
 494           <term><varname>IPv6PrivacyExtensions=</varname></term>
 495           <listitem><para>Configures use of stateless temporary
 496           addresses that change over time (see <ulink
 497           url="https://tools.ietf.org/html/rfc4941">RFC 4941</ulink>,
 498           Privacy Extensions for Stateless Address Autoconfiguration
 499           in IPv6). Takes a boolean or the special values
 500           <literal>prefer-public</literal> and
 501           <literal>kernel</literal>. When true, enables the privacy
 502           extensions and prefers temporary addresses over public
 503           addresses. When <literal>prefer-public</literal>, enables the
 504           privacy extensions, but prefers public addresses over
 505           temporary addresses. When false, the privacy extensions
 506           remain disabled. When <literal>kernel</literal>, the kernel's
 507           default setting will be left in place.  Defaults to
 508           <literal>no</literal>.</para></listitem>
 509         </varlistentry>
 510         <varlistentry>
 511           <term><varname>IPv6AcceptRouterAdvertisements=</varname></term>
 512           <listitem><para>Force the setting of the <filename>accept_ra</filename>
 513           (router advertisements) setting for the interface.
 514           When unset, the kernel default is used, and router
 515           advertisements are accepted only when local forwarding
 516           is disabled for that interface.
 517           When router advertisements are accepted, they will
 518           trigger the start of the DHCPv6 client if the relevant
 519           flags are passed, or if no routers are found on the link.
 520           Takes a boolean. If true, router advertisements are
 521           accepted, when false, router advertisements are ignored,
 522           independently of the local forwarding state.</para>
 523
 524           <para>See
 525           <ulink url="https://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt">ip-sysctl.txt</ulink>
 526           in the kernel documentation, but note that systemd's
 527           setting of <constant>1</constant> corresponds to
 528           kernel's setting of <constant>2</constant>.</para>
 529         </listitem>
 530         </varlistentry>
 531         <varlistentry>
 532           <term><varname>IPv6DuplicateAddressDetection=</varname></term>
 533           <listitem><para>Configures the amount of IPv6 Duplicate
 534           Address Detection (DAD) probes to send. Defaults to unset.
 535         </para></listitem>
 536         </varlistentry>
 537         <varlistentry>
 538           <term><varname>IPv6HopLimit=</varname></term>
 539           <listitem><para>Configures IPv6 Hop Limit. For each router that
 540           forwards the packet, the hop limit is decremented by 1. When the
 541           hop limit field reaches zero, the packet is discarded.
 542           Defaults to unset.
 543         </para></listitem>
 544         </varlistentry>
 545         <varlistentry>
 546           <term><varname>Bridge=</varname></term>
 547           <listitem>
 548             <para>The name of the bridge to add the link to.</para>
 549           </listitem>
 550         </varlistentry>
 551         <varlistentry>
 552           <term><varname>Bond=</varname></term>
 553           <listitem>
 554             <para>The name of the bond to add the link to.</para>
 555           </listitem>
 556         </varlistentry>
 557         <varlistentry>
 558           <term><varname>VLAN=</varname></term>
 559           <listitem>
 560             <para>The name of a VLAN to create on the link. This
 561             option may be specified more than once.</para>
 562           </listitem>
 563         </varlistentry>
 564         <varlistentry>
 565           <term><varname>MACVLAN=</varname></term>
 566           <listitem>
 567             <para>The name of a MACVLAN to create on the link. This
 568             option may be specified more than once.</para>
 569           </listitem>
 570         </varlistentry>
 571         <varlistentry>
 572           <term><varname>VXLAN=</varname></term>
 573           <listitem>
 574             <para>The name of a VXLAN to create on the link. This
 575             option may be specified more than once.</para>
 576           </listitem>
 577         </varlistentry>
 578         <varlistentry>
 579           <term><varname>Tunnel=</varname></term>
 580           <listitem>
 581             <para>The name of a Tunnel to create on the link. This
 582             option may be specified more than once.</para>
 583           </listitem>
 584         </varlistentry>
 585       </variablelist>
 586
 587   </refsect1>
 588
 589   <refsect1>
 590     <title>[Address] Section Options</title>
 591
 592       <para>An <literal>[Address]</literal> section accepts the
 593       following keys. Specify several <literal>[Address]</literal>
 594       sections to configure several addresses.</para>
 595
 596       <variablelist class='network-directives'>
 597         <varlistentry>
 598           <term><varname>Address=</varname></term>
 599           <listitem>
 600             <para>As in the <literal>[Network]</literal> section. This
 601             key is mandatory.</para>
 602           </listitem>
 603         </varlistentry>
 604         <varlistentry>
 605           <term><varname>Peer=</varname></term>
 606           <listitem>
 607             <para>The peer address in a point-to-point connection.
 608             Accepts the same format as the <literal>Address</literal>
 609             key.</para>
 610           </listitem>
 611         </varlistentry>
 612         <varlistentry>
 613           <term><varname>Broadcast=</varname></term>
 614           <listitem>
 615             <para>The broadcast address, which must be in the format
 616             described in
 617             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 618             This key only applies to IPv4 addresses. If it is not
 619             given, it is derived from the <literal>Address</literal>
 620             key.</para>
 621           </listitem>
 622         </varlistentry>
 623         <varlistentry>
 624           <term><varname>Label=</varname></term>
 625           <listitem>
 626             <para>An address label.</para>
 627           </listitem>
 628         </varlistentry>
 629       </variablelist>
 630   </refsect1>
 631
 632   <refsect1>
 633     <title>[Route] Section Options</title>
 634       <para>The <literal>[Route]</literal> section accepts the
 635       following keys. Specify several <literal>[Route]</literal>
 636       sections to configure several routes.</para>
 637
 638       <variablelist class='network-directives'>
 639         <varlistentry>
 640           <term><varname>Gateway=</varname></term>
 641           <listitem>
 642             <para>As in the <literal>[Network]</literal> section.</para>
 643           </listitem>
 644         </varlistentry>
 645         <varlistentry>
 646           <term><varname>Destination=</varname></term>
 647           <listitem>
 648             <para>The destination prefix of the route. Possibly
 649             followed by a slash and the prefix length. If omitted, a
 650             full-length host route is assumed.</para>
 651           </listitem>
 652         </varlistentry>
 653         <varlistentry>
 654           <term><varname>Source=</varname></term>
 655           <listitem>
 656             <para>The source prefix of the route. Possibly followed by
 657             a slash and the prefix length. If omitted, a full-length
 658             host route is assumed.</para>
 659           </listitem>
 660         </varlistentry>
 661         <varlistentry>
 662           <term><varname>Metric=</varname></term>
 663           <listitem>
 664             <para>The metric of the route (an unsigned integer).</para>
 665           </listitem>
 666         </varlistentry>
 667         <varlistentry>
 668           <term><varname>Scope=</varname></term>
 669           <listitem>
 670             <para>The scope of the route, which can be <literal>global</literal>,
 671             <literal>link</literal> or <literal>host</literal>. Defaults to
 672             <literal>global</literal>.</para>
 673           </listitem>
 674         </varlistentry>
 675         <varlistentry>
 676           <term><varname>PreferredSource=</varname></term>
 677           <listitem>
 678             <para>The preferred source address of the route. The address
 679             must be in the format described in
 680             <citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
 681           </listitem>
 682         </varlistentry>
 683       </variablelist>
 684   </refsect1>
 685
 686   <refsect1>
 687     <title>[DHCP] Section Options</title>
 688       <para>The <literal>[DHCP]</literal> section configures the
 689       DHCPv4 and DHCP6 client, if it is enabled with the
 690       <varname>DHCP=</varname> setting described above:</para>
 691
 692       <variablelist class='network-directives'>
 693         <varlistentry>
 694           <term><varname>UseDNS=</varname></term>
 695           <listitem>
 696             <para>When true (the default), the DNS servers received
 697             from the DHCP server will be used and take precedence over
 698             any statically configured ones.</para>
 699
 700             <para>This corresponds to the <option>nameserver</option>
 701             option in <citerefentry
 702             project='man-pages'><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 703           </listitem>
 704         </varlistentry>
 705         <varlistentry>
 706           <term><varname>UseNTP=</varname></term>
 707           <listitem>
 708             <para>When true (the default), the NTP servers received
 709             from the DHCP server will be used by systemd-timesyncd
 710             and take precedence over any statically configured ones.</para>
 711           </listitem>
 712         </varlistentry>
 713         <varlistentry>
 714           <term><varname>UseMTU=</varname></term>
 715           <listitem>
 716             <para>When true, the interface maximum transmission unit
 717             from the DHCP server will be used on the current link.
 718             Defaults to false.</para>
 719           </listitem>
 720         </varlistentry>
 721         <varlistentry>
 722           <term><varname>SendHostname=</varname></term>
 723           <listitem>
 724             <para>When true (the default), the machine's hostname will
 725             be sent to the DHCP server.</para>
 726           </listitem>
 727         </varlistentry>
 728         <varlistentry>
 729           <term><varname>UseHostname=</varname></term>
 730           <listitem>
 731             <para>When true (the default), the hostname received from
 732             the DHCP server will be set as the transient hostname of the system
 733             </para>
 734           </listitem>
 735         </varlistentry>
 736         <varlistentry>
 737         <term><varname>Hostname=</varname></term>
 738         <listitem>
 739           <para>Use this value for the hostname which is sent to the
 740           DHCP server, instead of machine's hostname.</para>
 741         </listitem>
 742       </varlistentry>
 743         <varlistentry>
 744           <term><varname>UseDomains=</varname></term>
 745           <listitem>
 746             <para>Takes a boolean argument, or the special value <literal>route</literal>. When true, the domain name
 747             received from the DHCP server will be used as DNS search domain over this link, similar to the effect of
 748             the <option>Domains=</option> setting. If set to <literal>route</literal>, the domain name received from
 749             the DHCP server will be used for routing DNS queries only, but not for searching, similar to the effect of
 750             the <option>Domains=</option> setting when the argument is prefixed with <literal>~</literal>. Defaults to
 751             false.</para>
 752
 753             <para>It is recommended to enable this option only on trusted networks, as setting this affects resolution
 754             of all host names, in particular to single-label names. It is generally safer to use the supplied domain
 755             only as routing domain, rather than as search domain, in order to not have it affect local resolution of
 756             single-label names.</para>
 757
 758             <para>When set to true, this setting corresponds to the <option>domain</option> option in <citerefentry
 759             project='man-pages'><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 760           </listitem>
 761         </varlistentry>
 762         <varlistentry>
 763           <term><varname>UseRoutes=</varname></term>
 764           <listitem>
 765             <para>When true (the default), the static routes will be
 766             requested from the DHCP server and added to the routing
 767             table with a metric of 1024.</para>
 768           </listitem>
 769         </varlistentry>
 770
 771         <varlistentry>
 772           <term><varname>UseTimezone=</varname></term>
 773
 774           <listitem><para>When true, the timezone received from the
 775           DHCP server will be set as timezone of the local
 776           system. Defaults to <literal>no</literal>.</para></listitem>
 777         </varlistentry>
 778
 779         <varlistentry>
 780           <term><varname>CriticalConnection=</varname></term>
 781           <listitem>
 782             <para>When true, the connection will never be torn down
 783             even if the DHCP lease expires. This is contrary to the
 784             DHCP specification, but may be the best choice if, say,
 785             the root filesystem relies on this connection. Defaults to
 786             false.</para>
 787           </listitem>
 788         </varlistentry>
 789         <varlistentry>
 790           <term><varname>ClientIdentifier=</varname></term>
 791           <listitem>
 792             <para>DHCP client identifier to use. Either <literal>mac</literal>
 793             to use the MAC address of the link or <literal>duid</literal>
 794             (the default) to use a RFC4361-compliant Client ID.</para>
 795           </listitem>
 796         </varlistentry>
 797         <varlistentry>
 798           <term><varname>VendorClassIdentifier=</varname></term>
 799           <listitem>
 800             <para>The vendor class identifier used to identify vendor
 801             type and configuration.</para>
 802           </listitem>
 803         </varlistentry>
 804         <varlistentry>
 805           <term><varname>RequestBroadcast=</varname></term>
 806           <listitem>
 807             <para>Request the server to use broadcast messages before
 808             the IP address has been configured. This is necessary for
 809             devices that cannot receive RAW packets, or that cannot
 810             receive packets at all before an IP address has been
 811             configured. On the other hand, this must not be enabled on
 812             networks where broadcasts are filtered out.</para>
 813           </listitem>
 814         </varlistentry>
 815         <varlistentry>
 816           <term><varname>RouteMetric=</varname></term>
 817           <listitem>
 818             <para>Set the routing metric for routes specified by the
 819             DHCP server.</para>
 820           </listitem>
 821         </varlistentry>
 822       </variablelist>
 823
 824   </refsect1>
 825
 826   <refsect1>
 827     <title>[DHCPServer] Section Options</title>
 828     <para>The <literal>[DHCPServer]</literal> section contains
 829     settings for the DHCP server, if enabled via the
 830     <varname>DHCPServer=</varname> option described above:</para>
 831
 832     <variablelist class='network-directives'>
 833
 834       <varlistentry>
 835         <term><varname>PoolOffset=</varname></term>
 836         <term><varname>PoolSize=</varname></term>
 837
 838         <listitem><para>Configures the pool of addresses to hand out. The pool
 839         is a contiguous sequence of IP addresses in the subnet configured for
 840         the server address, which does not include the subnet nor the broadcast
 841         address. <varname>PoolOffset=</varname> takes the offset of the pool
 842         from the start of subnet, or zero to use the default value.
 843         <varname>PoolSize=</varname> takes the number of IP addresses in the
 844         pool or zero to use the default value. By default, the pool starts at
 845         the first address after the subnet address and takes up the rest of
 846         the subnet, excluding the broadcast address. If the pool includes
 847         the server address (the default), this is reserved and not handed
 848         out to clients.</para></listitem>
 849       </varlistentry>
 850
 851       <varlistentry>
 852         <term><varname>DefaultLeaseTimeSec=</varname></term>
 853         <term><varname>MaxLeaseTimeSec=</varname></term>
 854
 855         <listitem><para>Control the default and maximum DHCP lease
 856         time to pass to clients. These settings take time values in seconds or
 857         another common time unit, depending on the suffix. The default
 858         lease time is used for clients that did not ask for a specific
 859         lease time. If a client asks for a lease time longer than the
 860         maximum lease time, it is automatically shortened to the
 861         specified time. The default lease time defaults to 1h, the
 862         maximum lease time to 12h. Shorter lease times are beneficial
 863         if the configuration data in DHCP leases changes frequently
 864         and clients shall learn the new settings with shorter
 865         latencies. Longer lease times reduce the generated DHCP
 866         network traffic.</para></listitem>
 867       </varlistentry>
 868
 869       <varlistentry>
 870         <term><varname>EmitDNS=</varname></term>
 871         <term><varname>DNS=</varname></term>
 872
 873         <listitem><para>Configures whether the DHCP leases handed out
 874         to clients shall contain DNS server information. The
 875         <varname>EmitDNS=</varname> setting takes a boolean argument
 876         and defaults to <literal>yes</literal>. The DNS servers to
 877         pass to clients may be configured with the
 878         <varname>DNS=</varname> option, which takes a list of IPv4
 879         addresses. If the <varname>EmitDNS=</varname> option is
 880         enabled but no servers configured, the servers are
 881         automatically propagated from an "uplink" interface that has
 882         appropriate servers set. The "uplink" interface is determined
 883         by the default route of the system with the highest
 884         priority. Note that this information is acquired at the time
 885         the lease is handed out, and does not take uplink interfaces
 886         into account that acquire DNS or NTP server information at a
 887         later point. DNS server propagation does not take
 888         <filename>/etc/resolv.conf</filename> into account. Also, note
 889         that the leases are not refreshed if the uplink network
 890         configuration changes. To ensure clients regularly acquire the
 891         most current uplink DNS server information, it is thus
 892         advisable to shorten the DHCP lease time via
 893         <varname>MaxLeaseTimeSec=</varname> described
 894         above.</para></listitem>
 895       </varlistentry>
 896
 897       <varlistentry>
 898         <term><varname>EmitNTP=</varname></term>
 899         <term><varname>NTP=</varname></term>
 900
 901         <listitem><para>Similar to the <varname>EmitDNS=</varname> and
 902         <varname>DNS=</varname> settings described above, these
 903         settings configure whether and what NTP server information
 904         shall be emitted as part of the DHCP lease. The same syntax,
 905         propagation semantics and defaults apply as for
 906         <varname>EmitDNS=</varname> and
 907         <varname>DNS=</varname>.</para></listitem>
 908       </varlistentry>
 909
 910       <varlistentry>
 911         <term><varname>EmitTimezone=</varname></term>
 912         <term><varname>Timezone=</varname></term>
 913
 914         <listitem><para>Configures whether the DHCP leases handed out
 915         to clients shall contain timezone information. The
 916         <varname>EmitTimezone=</varname> setting takes a boolean
 917         argument and defaults to <literal>yes</literal>. The
 918         <varname>Timezone=</varname> setting takes a timezone string
 919         (such as <literal>Europe/Berlin</literal> or
 920         <literal>UTC</literal>) to pass to clients. If no explicit
 921         timezone is set, the system timezone of the local host is
 922         propagated, as determined by the
 923         <filename>/etc/localtime</filename> symlink.</para></listitem>
 924       </varlistentry>
 925
 926     </variablelist>
 927   </refsect1>
 928
 929   <refsect1>
 930     <title>[Bridge] Section Options</title>
 931       <para>The <literal>[Bridge]</literal> section accepts the
 932       following keys.</para>
 933       <variablelist class='network-directives'>
 934         <varlistentry>
 935           <term><varname>UnicastFlood=</varname></term>
 936           <listitem>
 937             <para>A boolean. Controls whether the bridge should flood
 938             traffic for which an FDB entry is missing and the destination
 939             is unknown through this port. Defaults to on.
 940             </para>
 941           </listitem>
 942         </varlistentry>
 943         <varlistentry>
 944           <term><varname>HairPin=</varname></term>
 945           <listitem>
 946             <para>A boolean. Configures whether traffic may be sent back
 947             out of the port on which it was received. By default, this
 948             flag is false, and the bridge will not forward traffic back
 949             out of the receiving port.</para>
 950           </listitem>
 951         </varlistentry>
 952         <varlistentry>
 953           <term><varname>UseBPDU=</varname></term>
 954           <listitem>
 955             <para>A boolean. Configures whether STP Bridge Protocol Data Units will be
 956             processed by the bridge port. Defaults to yes.</para>
 957           </listitem>
 958         </varlistentry>
 959         <varlistentry>
 960           <term><varname>FastLeave=</varname></term>
 961           <listitem>
 962             <para>A boolean. This flag allows the bridge to immediately stop multicast
 963             traffic on a port that receives an IGMP Leave message. It is only used with
 964             IGMP snooping if enabled on the bridge. Defaults to off.</para>
 965           </listitem>
 966         </varlistentry>
 967         <varlistentry>
 968           <term><varname>AllowPortToBeRoot=</varname></term>
 969           <listitem>
 970             <para>A boolean. Configures whether a given port is allowed to
 971             become a root port. Only used when STP is enabled on the bridge.
 972             Defaults to on.</para>
 973           </listitem>
 974         </varlistentry>
 975         <varlistentry>
 976           <term><varname>Cost=</varname></term>
 977           <listitem>
 978             <para>Sets the "cost" of sending packets of this interface.
 979             Each port in a bridge may have a different speed and the cost
 980             is used to decide which link to use. Faster interfaces
 981             should have lower costs.</para>
 982           </listitem>
 983         </varlistentry>
 984       </variablelist>
 985   </refsect1>
 986   <refsect1>
 987     <title>[BridgeFDB] Section Options</title>
 988       <para>The <literal>[BridgeFDB]</literal> section manages the
 989       forwarding database table of a port and accepts the following
 990       keys. Specify several <literal>[BridgeFDB]</literal> sections to
 991       configure several static MAC table entries.</para>
 992
 993       <variablelist class='network-directives'>
 994         <varlistentry>
 995           <term><varname>MACAddress=</varname></term>
 996           <listitem>
 997             <para>As in the <literal>[Network]</literal> section. This
 998             key is mandatory.</para>
 999           </listitem>
1000         </varlistentry>
1001         <varlistentry>
1002           <term><varname>VLANId=</varname></term>
1003           <listitem>
1004             <para>The VLAN ID for the new static MAC table entry. If
1005             omitted, no VLAN ID info is appended to the new static MAC
1006             table entry.</para>
1007           </listitem>
1008         </varlistentry>
1009       </variablelist>
1010   </refsect1>
1011
1012   <refsect1>
1013     <title>Example</title>
1014     <example>
1015       <title>/etc/systemd/network/50-static.network</title>
1016
1017       <programlisting>[Match]
1018 Name=enp2s0
1019
1020 [Network]
1021 Address=192.168.0.15/24
1022 Gateway=192.168.0.1</programlisting>
1023     </example>
1024
1025     <example>
1026       <title>/etc/systemd/network/80-dhcp.network</title>
1027
1028       <programlisting>[Match]
1029 Name=en*
1030
1031 [Network]
1032 DHCP=yes</programlisting>
1033     </example>
1034
1035     <example>
1036       <title>/etc/systemd/network/25-bridge-static.network</title>
1037
1038       <programlisting>[Match]
1039 Name=bridge0
1040
1041 [Network]
1042 Address=192.168.0.15/24
1043 Gateway=192.168.0.1
1044 DNS=192.168.0.1</programlisting>
1045     </example>
1046
1047     <example>
1048       <title>/etc/systemd/network/25-bridge-slave-interface.network</title>
1049
1050       <programlisting>[Match]
1051 Name=enp2s0
1052
1053 [Network]
1054 Bridge=bridge0</programlisting>
1055     </example>
1056     <example>
1057       <title>/etc/systemd/network/25-ipip.network</title>
1058
1059       <programlisting>[Match]
1060 Name=em1
1061
1062 [Network]
1063 Tunnel=ipip-tun</programlisting>
1064     </example>
1065
1066     <example>
1067       <title>/etc/systemd/network/25-sit.network</title>
1068
1069       <programlisting>[Match]
1070 Name=em1
1071
1072 [Network]
1073 Tunnel=sit-tun</programlisting>
1074     </example>
1075
1076     <example>
1077       <title>/etc/systemd/network/25-gre.network</title>
1078
1079       <programlisting>[Match]
1080 Name=em1
1081
1082 [Network]
1083 Tunnel=gre-tun</programlisting>
1084     </example>
1085
1086     <example>
1087       <title>/etc/systemd/network/25-vti.network</title>
1088
1089       <programlisting>[Match]
1090 Name=em1
1091
1092 [Network]
1093 Tunnel=vti-tun</programlisting>
1094     </example>
1095
1096     <example>
1097       <title>/etc/systemd/network/25-bond.network</title>
1098
1099       <programlisting>[Match]
1100 Name=bond1
1101
1102 [Network]
1103 DHCP=yes
1104 </programlisting>
1105     </example>
1106
1107   </refsect1>
1108
1109   <refsect1>
1110     <title>See Also</title>
1111     <para>
1112       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1113       <citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
1114       <citerefentry><refentrytitle>systemd.link</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1115       <citerefentry><refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1116       <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
1117     </para>
1118   </refsect1>
1119
1120 </refentry>