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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"

"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">

<refentry id="systemd.network" conditional='ENABLE_NETWORKD'>

<refentryinfo>

<title>systemd.network</title>

<productname>systemd</productname>

<authorgroup>

<author>

<contrib>Developer</contrib>

<firstname>Tom</firstname>

<surname>Gundersen</surname>

<email>teg@jklm.no</email>

</author>

</authorgroup>

</refentryinfo>

<refmeta>

<refentrytitle>systemd.network</refentrytitle>

<manvolnum>5</manvolnum>

</refmeta>

<refnamediv>

<refname>systemd.network</refname>

<refpurpose>Network configuration</refpurpose>

</refnamediv>

<refsynopsisdiv>

<para><filename><replaceable>network</replaceable>.network</filename></para>

</refsynopsisdiv>

<refsect1>

<title>Description</title>

<para>Network setup is performed by

<citerefentry><refentrytitle>systemd-networkd</refentrytitle><manvolnum>8</manvolnum></citerefentry>.

</para>

<para>Network files must have the extension

<filename>.network</filename>; other extensions are ignored.

Networks are applied to links whenever the links appear.</para>

<para>The <filename>.network</filename> files are read from the

files located in the system network directory

<filename>/usr/lib/systemd/network</filename>, the volatile

runtime network directory

<filename>/run/systemd/network</filename> and the local

administration network directory

<filename>/etc/systemd/network</filename>. 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

<filename>/etc</filename> have the highest priority, files in

<filename>/run</filename> take precedence over files with the same

name in <filename>/usr/lib</filename>. 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 <filename>/dev/null</filename>

disables the configuration file entirely (it is "masked").</para>

</refsect1>

<refsect1>

<title>[Match] Section Options</title>

<para>The network file contains a <literal>[Match]</literal>

section, which determines if a given network file may be applied

to a given device; and a <literal>[Network]</literal> 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.</para>

<para>A network file is said to match a device if each of the

entries in the <literal>[Match]</literal> section matches, or if

the section is empty. The following keys are accepted:</para>

<variablelist class='network-directives'>

<varlistentry>

<term><varname>MACAddress=</varname></term>

<listitem>

<para>The hardware address.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>Path=</varname></term>

<listitem>

<para>A whitespace-separated list of shell-style globs

matching the persistent path, as exposed by the udev

property <literal>ID_PATH</literal>.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>Driver=</varname></term>

<listitem>

<para>A whitespace-separated list of shell-style globs

matching the driver currently bound to the device, as

exposed by the udev property <literal>DRIVER</literal>

of its parent device, or if that is not set the driver

as exposed by <literal>ethtool -i</literal> of the

device itself.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>Type=</varname></term>

<listitem>

<para>A whitespace-separated list of shell-style globs

matching the device type, as exposed by the udev property

<literal>DEVTYPE</literal>.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>Name=</varname></term>

<listitem>

<para>A whitespace-separated list of shell-style globs

matching the device name, as exposed by the udev property

<literal>INTERFACE</literal>.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>Host=</varname></term>

<listitem>

<para>Matches against the hostname or machine ID of the

host. See <literal>ConditionHost=</literal> in

<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>

for details.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>Virtualization=</varname></term>

<listitem>

<para>Checks whether the system is executed in a virtualized

environment and optionally test whether it is a specific

implementation. See <literal>ConditionVirtualization=</literal> in

<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>

for details.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>KernelCommandLine=</varname></term>

<listitem>

<para>Checks whether a specific kernel command line option is

set (or if prefixed with the exclamation mark unset). See

<literal>ConditionKernelCommandLine=</literal> in

<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>

for details.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>Architecture=</varname></term>

<listitem>

<para>Checks whether the system is running on a specific

architecture. See <literal>ConditionArchitecture=</literal> in

<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>

for details.

</para>

</listitem>

</varlistentry>

</variablelist>

</refsect1>

<refsect1>

<title>[Link] Section Options</title>

<para> The <literal>[Link]</literal> section accepts the following keys:</para>

<variablelist class='network-directives'>

<varlistentry>

<term><varname>MACAddress=</varname></term>

<listitem>

<para>The hardware address.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>MTUBytes=</varname></term>

<listitem>

<para>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.</para>

</listitem>

</varlistentry>

</variablelist>

</refsect1>

<refsect1>

<title>[Network] Section Options</title>

<para>The <literal>[Network]</literal> section accepts the following keys:</para>

<variablelist class='network-directives'>

<varlistentry>

<term><varname>Description=</varname></term>

<listitem>

<para>A description of the device. This is only used for

presentation purposes.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>DHCP=</varname></term>

<listitem>

<para>Enables DHCPv4 and/or DHCPv6 client support. Accepts

<literal>yes</literal>, <literal>no</literal>,

<literal>ipv4</literal>, or <literal>ipv6</literal>.</para>

<para>Please note that, by default, the domain name

specified through DHCP is not used for name resolution.

See option <option>UseDomains=</option> below.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>DHCPServer=</varname></term>

<listitem>

<para>A boolean. Enables DHCPv4 server support. Defaults

to <literal>no</literal>. Further settings for the DHCP

server may be set in the <literal>[DHCPServer]</literal>

section described below.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>LinkLocalAddressing=</varname></term>

<listitem>

<para>Enables link-local address autoconfiguration. Accepts

<literal>yes</literal>, <literal>no</literal>,

<literal>ipv4</literal>, or <literal>ipv6</literal>. Defaults to

<literal>ipv6</literal>.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>IPv4LLRoute=</varname></term>

<listitem>

<para>A boolean. When true, sets up the route needed for

non-IPv4LL hosts to communicate with IPv4LL-only hosts. Defaults

to false.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>IPv6Token=</varname></term>

<listitem>

<para>An IPv6 address with the top 64 bits unset. When set, indicates the

64-bit interface part of SLAAC IPv6 addresses for this link. By default,

it is autogenerated.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>LLMNR=</varname></term>

<listitem>

<para>A boolean or <literal>resolve</literal>. When true, enables

Link-Local Multicast Name Resolution on the link. When set to

<literal>resolve</literal>, only resolution is enabled, but not

announcement. Defaults to true.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>LLDP=</varname></term>

<listitem>

<para>A boolean. When true, enables LLDP link receive support.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>BindCarrier=</varname></term>

<listitem>

<para>A port or a list of ports. When set, controls the

behavior of the current interface. When all ports in the list

are in an operational down state, the current interface is brought

down. When at least one port has carrier, the current interface

is brought up.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>Address=</varname></term>

<listitem>

<para>A static IPv4 or IPv6 address and its prefix length,

separated by a <literal>/</literal> character. Specify

this key more than once to configure several addresses.

The format of the address must be as described in

<citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.

This is a short-hand for an [Address] section only

containing an Address key (see below). This option may be

specified more than once.

</para>

<para>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.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>Gateway=</varname></term>

<listitem>

<para>The gateway address, which must be in the format

described in

<citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.

This is a short-hand for a [Route] section only containing

a Gateway key. This option may be specified more than

once.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>DNS=</varname></term>

<listitem>

<para>A DNS server address, which must be in the format

described in

<citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.

This option may be specified more than once.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>Domains=</varname></term>

<listitem>

<para>The domains used for DNS resolution over this link.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>NTP=</varname></term>

<listitem>

<para>An NTP server address. This option may be specified more than once.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>IPForward=</varname></term>

<listitem><para>Configures IP forwarding for the network

interface. If enabled, incoming packets on the network

interface will be forwarded to other interfaces according to

the routing table. Takes either a boolean argument, or the

values <literal>ipv4</literal> or <literal>ipv6</literal>,

which only enables IP forwarding for the specified address

family, or <literal>kernel</literal>, which preserves existing sysctl settings.

This controls the

<filename>net.ipv4.conf.&lt;interface&gt;.forwarding</filename>

and

<filename>net.ipv6.conf.&lt;interface&gt;.forwarding</filename>

sysctl options of the network interface (see <ulink

url="https://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt">ip-sysctl.txt</ulink>

for details about sysctl options). Defaults to

<literal>no</literal>.</para>

<para>Note: unless this option is turned on, or set to <literal>kernel</literal>,

no IP forwarding is done on this interface, even if this is

globally turned on in the kernel, with the

<filename>net.ipv4.ip_forward</filename>,

<filename>net.ipv4.conf.all.forwarding</filename>, and

<filename>net.ipv6.conf.all.forwarding</filename> sysctl

options.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>IPMasquerade=</varname></term>

<listitem><para>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

<varname>IPForward=ipv4</varname>. Defaults to

<literal>no</literal>.</para></listitem>

</varlistentry>

<varlistentry>

<term><varname>IPv6PrivacyExtensions=</varname></term>

<listitem><para>Configures use of stateless temporary

addresses that change over time (see <ulink

url="https://tools.ietf.org/html/rfc4941">RFC 4941</ulink>,

Privacy Extensions for Stateless Address Autoconfiguration

in IPv6). Takes a boolean or the special values

<literal>prefer-public</literal> and

<literal>kernel</literal>. When true, enables the privacy

extensions and prefers temporary addresses over public

addresses. When <literal>prefer-public</literal>, enables the

privacy extensions, but prefers public addresses over

temporary addresses. When false, the privacy extensions

remain disabled. When <literal>kernel</literal>, the kernel's

default setting will be left in place. Defaults to

<literal>no</literal>.</para></listitem>

</varlistentry>

<varlistentry>

<term><varname>IPv6AcceptRouterAdvertisements=</varname></term>

<listitem><para>Force the setting of the <filename>accept_ra</filename>

(router advertisements) setting for the interface.

When unset, the kernel default is used, and router

advertisements are accepted only when local forwarding

is disabled for that interface.

Takes a boolean. If true, router advertisements are

accepted, when false, router advertisements are ignored,

independently of the local forwarding state.</para>

<para>See

<ulink url="https://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt">ip-sysctl.txt</ulink>

in the kernel documentation, but note that systemd's

setting of <constant>1</constant> corresponds to

kernel's setting of <constant>2</constant>.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>IPv6DuplicateAddressDetection=</varname></term>

<listitem><para>Configures the amount of IPv6 Duplicate

Address Detection (DAD) probes to send. Defaults to unset.

</para></listitem>

</varlistentry>

<varlistentry>

<term><varname>Bridge=</varname></term>

<listitem>

<para>The name of the bridge to add the link to.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>Bond=</varname></term>

<listitem>

<para>The name of the bond to add the link to.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>VLAN=</varname></term>

<listitem>

<para>The name of a VLAN to create on the link. This

option may be specified more than once.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>MACVLAN=</varname></term>

<listitem>

<para>The name of a MACVLAN to create on the link. This

option may be specified more than once.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>VXLAN=</varname></term>

<listitem>

<para>The name of a VXLAN to create on the link. This

option may be specified more than once.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>Tunnel=</varname></term>

<listitem>

<para>The name of a Tunnel to create on the link. This

option may be specified more than once.</para>

</listitem>

</varlistentry>

</variablelist>

</refsect1>

<refsect1>

<title>[Address] Section Options</title>

<para>An <literal>[Address]</literal> section accepts the

following keys. Specify several <literal>[Address]</literal>

sections to configure several addresses.</para>

<variablelist class='network-directives'>

<varlistentry>

<term><varname>Address=</varname></term>

<listitem>

<para>As in the <literal>[Network]</literal> section. This

key is mandatory.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>Peer=</varname></term>

<listitem>

<para>The peer address in a point-to-point connection.

Accepts the same format as the <literal>Address</literal>

key.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>Broadcast=</varname></term>

<listitem>

<para>The broadcast address, which must be in the format

described in

<citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.

This key only applies to IPv4 addresses. If it is not

given, it is derived from the <literal>Address</literal>

key.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>Label=</varname></term>

<listitem>

<para>An address label.</para>

</listitem>

</varlistentry>

</variablelist>

</refsect1>

<refsect1>

<title>[Route] Section Options</title>

<para>The <literal>[Route]</literal> section accepts the

following keys. Specify several <literal>[Route]</literal>

sections to configure several routes.</para>

<variablelist class='network-directives'>

<varlistentry>

<term><varname>Gateway=</varname></term>

<listitem>

<para>As in the <literal>[Network]</literal> section.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>Destination=</varname></term>

<listitem>

<para>The destination prefix of the route. Possibly

followed by a slash and the prefix length. If omitted, a

full-length host route is assumed.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>Source=</varname></term>

<listitem>

<para>The source prefix of the route. Possibly followed by

a slash and the prefix length. If omitted, a full-length

host route is assumed.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>Metric=</varname></term>

<listitem>

<para>The metric of the route (an unsigned integer).</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>Scope=</varname></term>

<listitem>

<para>The scope of the route, which can be <literal>global</literal>,

<literal>link</literal> or <literal>host</literal>. Defaults to

<literal>global</literal>.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>PreferredSource=</varname></term>

<listitem>

<para>The preferred source address of the route. The address

must be in the format described in

<citerefentry project='man-pages'><refentrytitle>inet_pton</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>

</listitem>

</varlistentry>

</variablelist>

</refsect1>

<refsect1>

<title>[DHCP] Section Options</title>

<para>The <literal>[DHCP]</literal> section configures the

DHCPv4 and DHCP6 client, if it is enabled with the

<varname>DHCP=</varname> setting described above:</para>

<variablelist class='network-directives'>

<varlistentry>

<term><varname>UseDNS=</varname></term>

<listitem>

<para>When true (the default), the DNS servers received

from the DHCP server will be used and take precedence over

any statically configured ones.</para>

<para>This corresponds to the <option>nameserver</option>

option in <citerefentry

project='man-pages'><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>UseNTP=</varname></term>

<listitem>

<para>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.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>UseMTU=</varname></term>

<listitem>

<para>When true, the interface maximum transmission unit

from the DHCP server will be used on the current link.

Defaults to false.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>SendHostname=</varname></term>

<listitem>

<para>When true (the default), the machine's hostname will

be sent to the DHCP server.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>UseHostname=</varname></term>

<listitem>

<para>When true (the default), the hostname received from

the DHCP server will be set as the transient hostname of the system

</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>Hostname=</varname></term>

<listitem>

<para>Use this value for the hostname which is sent to the

DHCP server, instead of machine's hostname.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>UseDomains=</varname></term>

<listitem>

<para>When true (not the default), the domain name

received from the DHCP server will be used for DNS

resolution over this link. When a name cannot be resolved

as specified, the domain name will be used a suffix and

name resolution of that will be attempted.</para>

<para>This corresponds to the <option>domain</option>

option in <citerefentry project='man-pages'><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>

and should not be enabled on untrusted networks.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>UseRoutes=</varname></term>

<listitem>

<para>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.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>UseTimezone=</varname></term>

<listitem><para>When true, the timezone received from the

DHCP server will be set as as timezone of the local

system. Defaults to <literal>no</literal>.</para></listitem>

</varlistentry>

<varlistentry>

<term><varname>CriticalConnection=</varname></term>

<listitem>

<para>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.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>ClientIdentifier=</varname></term>

<listitem>

<para>DHCP client identifier to use. Either <literal>mac</literal>

to use the MAC address of the link or <literal>duid</literal>

(the default) to use a RFC4361-compliant Client ID.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>VendorClassIdentifier=</varname></term>

<listitem>

<para>The vendor class identifier used to identify vendor

type and configuration.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>RequestBroadcast=</varname></term>

<listitem>

<para>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.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>RouteMetric=</varname></term>

<listitem>

<para>Set the routing metric for routes specified by the

DHCP server.</para>

</listitem>

</varlistentry>

</variablelist>

</refsect1>

<refsect1>

<title>[DHCPServer] Section Options</title>

<para>The <literal>[DHCPServer]</literal> section contains

settings for the DHCP server, if enabled via the

<varname>DHCPServer=</varname> option described above:</para>

<variablelist class='network-directives'>

<varlistentry>

<term><varname>PoolOffset=</varname></term>

<term><varname>PoolSize=</varname></term>

<listitem><para>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. <varname>PoolOffset=</varname> takes the offset of the pool

from the start of subnet, or zero to use the default value.

<varname>PoolSize=</varname> 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.</para></listitem>

</varlistentry>

<varlistentry>

<term><varname>DefaultLeaseTimeSec=</varname></term>

<term><varname>MaxLeaseTimeSec=</varname></term>

<listitem><para>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.</para></listitem>

</varlistentry>

<varlistentry>

<term><varname>EmitDNS=</varname></term>

<term><varname>DNS=</varname></term>

<listitem><para>Configures whether the DHCP leases handed out

to clients shall contain DNS server information. The

<varname>EmitDNS=</varname> setting takes a boolean argument

and defaults to <literal>yes</literal>. The DNS servers to

pass to clients may be configured with the

<varname>DNS=</varname> option, which takes a list of IPv4

addresses. If the <varname>EmitDNS=</varname> 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

<filename>/etc/resolv.conf</filename> 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

<varname>MaxLeaseTimeSec=</varname> described

above.</para></listitem>

</varlistentry>

<varlistentry>

<term><varname>EmitNTP=</varname></term>

<term><varname>NTP=</varname></term>

<listitem><para>Similar to the <varname>EmitDNS=</varname> and

<varname>DNS=</varname> 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

<varname>EmitDNS=</varname> and

<varname>DNS=</varname>.</para></listitem>

</varlistentry>

<varlistentry>

<term><varname>EmitTimezone=</varname></term>

<term><varname>Timezone=</varname></term>

<listitem><para>Configures whether the DHCP leases handed out

to clients shall contain timezone information. The

<varname>EmitTimezone=</varname> setting takes a boolean

argument and defaults to <literal>yes</literal>. The

<varname>Timezone=</varname> setting takes a timezone string

(such as <literal>Europe/Berlin</literal> or

<literal>UTC</literal>) to pass to clients. If no explicit

timezone is set, the system timezone of the local host is

propagated, as determined by the

<filename>/etc/localtime</filename> symlink.</para></listitem>

</varlistentry>

</variablelist>

</refsect1>

<refsect1>

<title>[Bridge] Section Options</title>

<para>The <literal>[Bridge]</literal> section accepts the

following keys.</para>

<variablelist class='network-directives'>

<varlistentry>

<term><varname>UnicastFlood=</varname></term>

<listitem>

<para>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.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>HairPin=</varname></term>

<listitem>

<para>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.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>UseBPDU=</varname></term>

<listitem>

<para>A boolean. Configures whether STP Bridge Protocol Data Units will be

processed by the bridge port. Defaults to yes.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>FastLeave=</varname></term>

<listitem>

<para>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.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>AllowPortToBeRoot=</varname></term>

<listitem>

<para>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.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>Cost=</varname></term>

<listitem>

<para>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.</para>

</listitem>

</varlistentry>

</variablelist>

</refsect1>

<refsect1>

<title>[BridgeFDB] Section Options</title>

<para>The <literal>[BridgeFDB]</literal> section manages the

forwarding database table of a port and accepts the following

keys. Specify several <literal>[BridgeFDB]</literal> sections to

configure several static MAC table entries.</para>

<variablelist class='network-directives'>

<varlistentry>

<term><varname>MACAddress=</varname></term>

<listitem>

<para>As in the <literal>[Network]</literal> section. This

key is mandatory.</para>

</listitem>

</varlistentry>

<varlistentry>

<term><varname>VLANId=</varname></term>

<listitem>

<para>The VLAN ID for the new static MAC table entry. If

omitted, no VLAN ID info is appended to the new static MAC

table entry.</para>

</listitem>

</varlistentry>

</variablelist>

</refsect1>

<refsect1>

<title>Example</title>

<example>

<title>/etc/systemd/network/50-static.network</title>

<programlisting>[Match]

Name=enp2s0

[Network]

Address=192.168.0.15/24

Gateway=192.168.0.1</programlisting>

</example>

<example>

<title>/etc/systemd/network/80-dhcp.network</title>

<programlisting>[Match]

Name=en*

[Network]

DHCP=yes</programlisting>

</example>

<example>

<title>/etc/systemd/network/25-bridge-static.network</title>

<programlisting>[Match]

Name=bridge0

[Network]

Address=192.168.0.15/24

Gateway=192.168.0.1

DNS=192.168.0.1</programlisting>

</example>

<example>

<title>/etc/systemd/network/25-bridge-slave-interface.network</title>

<programlisting>[Match]

Name=enp2s0

[Network]

Bridge=bridge0</programlisting>

</example>

<example>

<title>/etc/systemd/network/25-ipip.network</title>

<programlisting>[Match]

Name=em1

[Network]

Tunnel=ipip-tun</programlisting>

</example>

<example>

<title>/etc/systemd/network/25-sit.network</title>

<programlisting>[Match]

Name=em1

[Network]

Tunnel=sit-tun</programlisting>

</example>

<example>

<title>/etc/systemd/network/25-gre.network</title>

<programlisting>[Match]

Name=em1

[Network]

Tunnel=gre-tun</programlisting>

</example>

<example>

<title>/etc/systemd/network/25-vti.network</title>

<programlisting>[Match]

Name=em1

[Network]

Tunnel=vti-tun</programlisting>

</example>

<example>

<title>/etc/systemd/network/25-bond.network</title>

<programlisting>[Match]

Name=bond1

[Network]

DHCP=yes

</programlisting>

</example>

</refsect1>

<refsect1>

<title>See Also</title>

<para>

<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,

<citerefentry><refentrytitle>systemd-networkd</refentrytitle><manvolnum>8</manvolnum></citerefentry>,

<citerefentry><refentrytitle>systemd.link</refentrytitle><manvolnum>5</manvolnum></citerefentry>,

<citerefentry><refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum></citerefentry>

</para>

</refsect1>

</refentry>