SYSTEMD.NETWORK(5)systemd.networkSYSTEMD.NETWORK(5)NAMEsystemd.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.
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 is not 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. Defaults to "false". See the "[IPv6PrefixDelegation]" and the
"[IPv6Prefix]" sections for 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".
[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 false.
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.
[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 false.
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[14] 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 ALSOsystemd(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 4861
https://tools.ietf.org/html/rfc4861
systemd 236SYSTEMD.NETWORK(5)
