SYSTEMD.NETDEV(5)

NAME
systemd.netdev - Virtual Network Device configuration

SYNOPSIS

netdev.netdev

DESCRIPTION

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

The main Virtual Network Device file must have the extension .netdev; other extensions are ignored. Virtual network devices are created as soon as systemd-networkd is started if possible. If a netdev with the specified name already exists, systemd-networkd will try to update the config if the kind of the existing netdev is equivalent to the requested one, otherwise (e.g. when bridge device foo exists but bonding device with the same name is configured in a .netdev file) use the existing netdev as-is rather than replacing with the requested netdev. Note, several settings (e.g. vlan ID) cannot be changed after the netdev is created. To change such settings, it is necessary to first remove the existing netdev, and then run networkctl reload command or restart systemd-networkd. See also networkctl(1).

The .netdev files are read from the files located in the system network directory /usr/lib/systemd/network and /usr/local/lib/systemd/network, the volatile runtime network directory /run/systemd/network and the local administration network directory /etc/systemd/network. All configuration files are collectively sorted and processed in alphanumeric order, regardless of the directories in which they live. However, files with identical filenames replace each other. It is recommended that each filename is prefixed with a number smaller than "70" (e.g. 10-vlan.netdev). Otherwise, .netdev files generated by systemd-network-generator.service(8) may take precedence over user configured files. Files in /etc/ have the highest priority, files in /run/ take precedence over files with the same name in /usr/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 netdev file foo.netdev, a "drop-in" directory foo.netdev.d/ may exist. All files with the suffix ".conf" from this directory will be merged in the alphanumeric order and parsed after the main file itself has been 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 /usr/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 /usr/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.)

SUPPORTED NETDEV KINDS

The following kinds of virtual network devices may be configured in .netdev files:

Table 1. Supported kinds of virtual network devices
Kind | Description
bond | A bond device is an aggregation of all its slave devices. See Linux Ethernet Bonding Driver HOWTO[1] for details.
bridge | A bridge device is a software switch, and each of its slave devices and the bridge itself are ports of the switch.
dummy | A dummy device drops all packets sent to it.
gre | A Level 3 GRE tunnel over IPv4. See RFC 2784[2] for details. Name "gre0" should not be used, as the kernel creates a device with this name when the corresponding kernel module is loaded.
gretap | A Level 2 GRE tunnel over IPv4. Name "gretap0" should not be used, as the kernel creates a device with this name when the corresponding kernel module is loaded.
erspan | ERSPAN mirrors traffic on one or more source ports and delivers the mirrored traffic to one or more destination ports on another switch. The traffic is encapsulated in generic routing encapsulation (GRE) and is therefore routable across a layer 3 network between the source switch and the destination switch. Name "erspan0" should not be used, as the kernel creates a device with this name when the corresponding kernel module is loaded.
ip6gre | A Level 3 GRE tunnel over IPv6.
ip6tnl | An IPv4 or IPv6 tunnel over IPv6
ip6gretap | A Level 2 GRE tunnel over IPv6.
ipip | An IPv4 over IPv4 tunnel.
ipvlan | An IPVLAN device is a stacked device which receives packets from its underlying device based on IP address filtering.
ipvtap | An IPVTAP device is a stacked device which receives packets from its underlying device based on IP address filtering and can be accessed using the tap user space interface.
macvlan | A macvlan device is a stacked device which receives packets from its underlying device based on MAC address filtering.
macvtap | A macvtap device is a stacked device which receives packets from its underlying device based on MAC address filtering.
sit | An IPv6 over IPv4 tunnel.
tap | A persistent Level 2 tunnel between a network device and a device node.
tun | A persistent Level 3 tunnel between a network device and a device node.
veth | An Ethernet tunnel between a pair of network devices.
vlan | A VLAN is a stacked device which receives packets from its underlying device based on VLAN tagging. See IEEE 802.1Q[3] for details.
vti | An IPv4 over IPSec tunnel.
vti6 | An IPv6 over IPSec tunnel.
vxlan | A virtual extensible LAN (vxlan), for connecting Cloud computing deployments.
geneve | A GEneric NEtwork Virtualization Encapsulation (GENEVE) netdev driver.
hsr | A High-availability Seamless Redundancy (HSR) or Parallel Redundancy Protocol (PRP) interface. HSR and PRP are two protocols defined by the IEC 62439-3 standard, providing seamless failover against failure of any single network component.
l2tp | A Layer 2 Tunneling Protocol (L2TP) is a tunneling protocol used to support virtual private networks (VPNs) or as part of the delivery of services by ISPs. It does not provide any encryption or confidentiality by itself
macsec | Media Access Control Security (MACsec) is an 802.1AE IEEE industry-standard security technology that provides secure communication for all traffic on Ethernet links. MACsec provides point-to-point security on Ethernet links between directly connected nodes and is capable of identifying and preventing most security threats.
vrf | A Virtual Routing and Forwarding (VRF[4]) interface to create separate routing and forwarding domains.
vcan | The virtual CAN driver (vcan). Similar to the network loopback devices, vcan offers a virtual local CAN interface.
vxcan | The virtual CAN tunnel driver (vxcan). Similar to the virtual ethernet driver veth, vxcan implements a local CAN traffic tunnel between two virtual CAN network devices. When creating a vxcan, two vxcan devices are created as pair. When one end receives the packet it appears on its pair and vice versa. The vxcan can be used for cross namespace communication.
wireguard | WireGuard Secure Network Tunnel.
nlmon | A Netlink monitor device. Use an nlmon device when you want to monitor system Netlink messages.
fou | Foo-over-UDP tunneling.
xfrm | A virtual tunnel interface like vti/vti6 but with several advantages.
ifb | The Intermediate Functional Block (ifb) pseudo network interface acts as a QoS concentrator for multiple different sources of traffic.
bareudp | Bare UDP tunnels provide a generic L3 encapsulation support for tunnelling different L3 protocols like MPLS, IP etc. inside of a UDP tunnel.
batadv | B.A.T.M.A.N. Advanced[5] is a routing protocol for multi-hop mobile ad-hoc networks which operates on layer 2.
ipoib | An IP over Infiniband subinterface.
wlan | A virtual wireless network (WLAN) interface.

[MATCH] SECTION OPTIONS

A virtual network device is only created if the [Match] section matches the current environment, or if the section is empty. The following keys are accepted:

Host=
    Matches against the hostname or machine ID of the host. See ConditionHost= in systemd.unit(5) for details. When prefixed with an exclamation mark ("!"), the result is negated. If an empty string is assigned, the previously assigned value is cleared.

    Added in version 211.

Virtualization=
    Checks whether the system is executed in a virtualized environment and optionally test whether it is a specific implementation. See ConditionVirtualization= in systemd.unit(5) for details. When prefixed with an exclamation mark ("!"), the result is negated. If an empty string is assigned, the previously assigned value is cleared.

    Added in version 211.

KernelCommandLine=
    Checks whether a specific kernel command line option is set. See ConditionKernelCommandLine= in systemd.unit(5) for details. When prefixed with an exclamation mark ("!"), the result is negated. If an empty string is assigned, the previously assigned value is cleared.

    Added in version 211.

KernelVersion=
    Checks whether the kernel version (as reported by uname -r) matches a certain expression. See ConditionKernelVersion= in systemd.unit(5) for details. When prefixed with an exclamation mark ("!"), the result is negated. If an empty string is assigned, the previously assigned value is cleared.

    Added in version 237.

Version=
    Checks whether a software version matches a certain expression. See ConditionVersion= in systemd.unit(5) for details. When prefixed with an exclamation mark ("!"), the result is negated. If an empty string is assigned, the previously assigned value is cleared.

    Added in version 258.

Credential=
    Checks whether the specified credential was passed to the systemd-udevd.service service. See System and Service Credentials[6] for details. When prefixed with an exclamation mark ("!"), the result is negated. If an empty string is assigned, the previously assigned value is cleared.

    Added in version 252.

Architecture=
    Checks whether the system is running on a specific architecture. See ConditionArchitecture= in systemd.unit(5) for details. When prefixed with an exclamation mark ("!"), the result is negated. If an empty string is assigned, the previously assigned value is cleared.

    Added in version 211.

Firmware=
    Checks whether the system is running on a machine with the specified firmware. See ConditionFirmware= in systemd.unit(5) for details. When prefixed with an exclamation mark ("!"), the result is negated. If an empty string is assigned, the previously assigned value is cleared.

    Added in version 249.

[NETDEV] SECTION OPTIONS

The [NetDev] section accepts the following keys:

Description=
    A free-form description of the netdev.

    Added in version 215.

Name=
    The interface name used when creating the netdev. This setting is compulsory.

    Added in version 211.

Kind=
    The netdev kind. This setting is compulsory. See the "Supported netdev kinds" section for the valid keys.

    Added in version 211.

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. For "tun" or "tap" devices, MTUBytes= setting is not currently supported in [NetDev] section. Please specify it in [Link] section of corresponding systemd.network(5) files.

    Added in version 215.

MACAddress=
    Specifies the MAC address to use for the device, or takes the special value "none". When "none", systemd-networkd does not request the MAC address for the device, and the kernel will assign a random MAC address. For "tun", "tap", or "l2tp" devices, the MACAddress= setting in the [NetDev] section is not supported and will be ignored. Please specify it in the [Link] section of the corresponding systemd.network(5) file. If this option is not set, "vlan" device inherits the MAC address of the master interface. For other kind of netdevs, if this option is not set, then the MAC address is generated based on the interface name and the machine-id(5).

    Note, even if "none" is specified, systemd-udevd will assign the persistent MAC address for the device, as 99-default.link has MACAddressPolicy=persistent. So, it is also necessary to create a custom .link file for the device, if the MAC address assignment is not desired.

    Added in version 215.

[BRIDGE] SECTION OPTIONS

The [Bridge] section only applies for netdevs of kind "bridge", and accepts the following keys:

HelloTimeSec=
    HelloTimeSec specifies the number of seconds between two hello packets sent out by the root bridge and the designated bridges. Hello packets are used to communicate information about the topology throughout the entire bridged local area network.

    Added in version 227.

MaxAgeSec=
    MaxAgeSec specifies the number of seconds of maximum message age. If the last seen (received) hello packet is more than this number of seconds old, the bridge in question will start the takeover procedure in attempt to become the Root Bridge itself.

    Added in version 227.

ForwardDelaySec=
    ForwardDelaySec specifies the number of seconds spent in each of the Listening and Learning states before the Forwarding state is entered.

    Added in version 227.

AgeingTimeSec=
    This specifies the number of seconds a MAC Address will be kept in the forwarding database after having a packet received from this MAC Address.

    Added in version 232.

Priority=
    The priority of the bridge. An integer between 0 and 65535. A lower value means higher priority. The bridge having the lowest priority will be elected as root bridge.

    Added in version 232.

GroupForwardMask=
    A 16-bit bitmask represented as an integer which allows forwarding of link local frames with 802.1D reserved addresses (01:80:C2:00:00:0X). A logical AND is performed between the specified bitmask and the exponentiation of 2^X, the lower nibble of the last octet of the MAC address. For example, a value of 8 would allow forwarding of frames addressed to 01:80:C2:00:00:03 (802.1X PAE).

    Added in version 235.

DefaultPVID=
    This specifies the default port VLAN ID of a newly attached bridge port. Set this to an integer in the range 1...4094 or "none" to disable the PVID.

    Added in version 232.

MulticastQuerier=
    Takes a boolean. This setting controls the IFLA_BR_MCAST_QUERIER option in the kernel. If enabled, the kernel will send general ICMP queries from a zero source address. This feature should allow faster convergence on startup, but it causes some multicast-aware switches to misbehave and disrupt forwarding of multicast packets. When unset, the kernel's default will be used.

    Added in version 230.

MulticastSnooping=
    Takes a boolean. This setting controls the IFLA_BR_MCAST_SNOOPING option in the kernel. If enabled, IGMP snooping monitors the Internet Group Management Protocol (IGMP) traffic between hosts and multicast routers. When unset, the kernel's default will be used.

    Added in version 230.

VLANFiltering=
    Takes a boolean. This setting controls the IFLA_BR_VLAN_FILTERING option in the kernel. If enabled, the bridge will be started in VLAN-filtering mode. When unset, the kernel's default will be used.

    Added in version 231.

VLANProtocol=
    Allows setting the protocol used for VLAN filtering. Takes 802.1q or, 802.1ad, and defaults to unset and kernel's default is used.

    Added in version 246.

STP=
    Takes a boolean. This enables the bridge's Spanning Tree Protocol (STP). When unset, the kernel's default will be used.

    Added in version 232.

MulticastIGMPVersion=
    Allows changing bridge's multicast Internet Group Management Protocol (IGMP) version. Takes an integer 2 or 3. When unset, the kernel's default will be used.

    Added in version 243.

FDBMaxLearned=
    Specifies the maximum number of learned Ethernet addresses for the bridge. When the limit is reached, no more addresses are learned. When unset, the kernel's default will be used. 0 disables the limit.

    Added in version 257.

LinkLocalLearning=
    Takes a boolean. This enables learning source addresses from link local frames. When unset, the kernel's default will be used.

    Added in version 258.

[VLAN] SECTION OPTIONS

The [VLAN] section only applies for netdevs of kind "vlan", and accepts the following key:

Id=
    The VLAN ID to use. An integer in the range 0...4094. This setting is compulsory.

    Added in version 211.

Protocol=
    Allows setting the protocol used for the VLAN interface. Takes "802.1q" or, "802.1ad", and defaults to unset and kernel's default is used.

    Added in version 248.

GVRP=
    Takes a boolean. The Generic VLAN Registration Protocol (GVRP) is a protocol that allows automatic learning of VLANs on a network. When unset, the kernel's default will be used.

    Added in version 234.

MVRP=
    Takes a boolean. Multiple VLAN Registration Protocol (MVRP) formerly known as GARP VLAN Registration Protocol (GVRP) is a standards-based Layer 2 network protocol, for automatic configuration of VLAN information on switches. It was defined in the 802.1ak amendment to 802.1Q-2005. When unset, the kernel's default will be used.

    Added in version 234.

LooseBinding=
    Takes a boolean. The VLAN loose binding mode, in which only the operational state is passed from the parent to the associated VLANs, but the VLAN device state is not changed. When unset, the kernel's default will be used.

    Added in version 234.

ReorderHeader=
    Takes a boolean. When enabled, the VLAN reorder header is used and VLAN interfaces behave like physical interfaces. When unset, the kernel's default will be used.

    Added in version 234.

EgressQOSMaps=, IngressQOSMaps=
    Defines a mapping of Linux kernel internal packet priority (SO_PRIORITY) to VLAN header PCP field for outgoing and incoming frames, respectively. Takes a whitespace-separated list of integer pairs, where each integer must be in the range 1...4294967294, in the format "from"-"to", e.g., "21-7 45-5". Note that "from" must be greater than or equal to "to". When unset, the kernel's default will be used.

    Added in version 248.

[MACVLAN] SECTION OPTIONS

The [MACVLAN] section only applies for netdevs of kind "macvlan", and accepts the following key:

Mode=
    The MACVLAN mode to use. The supported options are "private", "vepa", "bridge", "passthru", and "source".

    Added in version 211.

SourceMACAddress=
    A whitespace-separated list of remote hardware addresses allowed on the MACVLAN. This option only has an effect in source mode. Use full colon-, hyphen- or dot-delimited hexadecimal. This option may appear more than once, in which case the lists are merged. If the empty string is assigned to this option, the list of hardware addresses defined prior to this is reset. Defaults to unset.

    Added in version 246.

BroadcastMulticastQueueLength=
    Specifies the length of the receive queue for broadcast/multicast packets. An unsigned integer in the range 0...4294967294. Defaults to unset.

    Added in version 248.

BroadcastQueueThreshold=
    Controls the threshold for broadcast queueing of the macvlan device. Takes the special value "no", or an integer in the range 0...2147483647. When "no" is specified, the broadcast queueing is disabled altogether. When an integer is specified, a multicast address will be queued as broadcast if the number of devices using the macvlan is greater than the given value. Defaults to unset, and the kernel default will be used.

    Added in version 256.

[MACVTAP] SECTION OPTIONS

The [MACVTAP] section applies for netdevs of kind "macvtap" and accepts the same keys as [MACVLAN].

[IPVLAN] SECTION OPTIONS

The [IPVLAN] section only applies for netdevs of kind "ipvlan", and accepts the following key:

Mode=
    The IPVLAN mode to use. The supported options are "L2","L3" and "L3S".

    Added in version 219.

Flags=
    The IPVLAN flags to use. The supported options are "bridge","private" and "vepa".

    Added in version 237.

[IPVTAP] SECTION OPTIONS

The [IPVTAP] section only applies for netdevs of kind "ipvtap" and accepts the same keys as [IPVLAN].

[VXLAN] SECTION OPTIONS

The [VXLAN] section only applies for netdevs of kind "vxlan", and accepts the following keys:

VNI=
    The VXLAN Network Identifier (or VXLAN Segment ID). Takes a number in the range 1...16777215. Ignored if External= is set to true.

    Added in version 243.

Remote=
    Configures destination IP address.

    Added in version 233.

Local=
    Configures local IP address. It must be an address on the underlying interface of the VXLAN interface, or one of the special values "ipv4_link_local", "ipv6_link_local", "dhcp4", "dhcp6", and "slaac". If one of the special values is specified, an address which matches the corresponding type on the underlying interface will be used. Defaults to unset.

    Added in version 233.

Group=
    Configures VXLAN multicast group IP address. All members of a VXLAN must use the same multicast group address.

    Added in version 243.

TOS=
    The Type Of Service byte value for a vxlan interface.

    Added in version 215.

TTL=
    A fixed Time To Live N on Virtual eXtensible Local Area Network packets. Takes "inherit" or a number in the range 0...255. 0 is a special value meaning inherit the inner protocol's TTL value. "inherit" means that it will inherit the outer protocol's TTL value.

    Added in version 215.

MacLearning=
    Takes a boolean. When true, enables dynamic MAC learning to discover remote MAC addresses.

    Added in version 215.

FDBAgeingSec=
    The lifetime of Forwarding Database entry learnt by the kernel, in seconds.

    Added in version 218.

MaximumFDBEntries=
    Configures maximum number of FDB entries.

    Added in version 228.

ReduceARPProxy=
    Takes a boolean. When true, bridge-connected VXLAN tunnel endpoint answers ARP requests from the local bridge on behalf of remote Distributed Overlay Virtual Ethernet (DOVE)[7] clients. Defaults to false.

    Added in version 233.

L2MissNotification=
    Takes a boolean. When true, enables netlink LLADDR miss notifications.

    Added in version 218.

L3MissNotification=
    Takes a boolean. When true, enables netlink IP address miss notifications.

    Added in version 218.

RouteShortCircuit=
    Takes a boolean. When true, route short circuiting is turned on.

    Added in version 218.

UDPChecksum=
    Takes a boolean. When true, transmitting UDP checksums when doing VXLAN/IPv4 is turned on.

    Added in version 220.

UDP6ZeroChecksumTx=
    Takes a boolean. When true, sending zero checksums in VXLAN/IPv6 is turned on.

    Added in version 220.

UDP6ZeroChecksumRx=
    Takes a boolean. When true, receiving zero checksums in VXLAN/IPv6 is turned on.

    Added in version 220.

RemoteChecksumTx=
    Takes a boolean. When true, remote transmit checksum offload of VXLAN is turned on.

    Added in version 232.

RemoteChecksumRx=
    Takes a boolean. When true, remote receive checksum offload in VXLAN is turned on.

    Added in version 232.

GroupPolicyExtension=
    Takes a boolean. When true, it enables Group Policy VXLAN extension security label mechanism across network peers based on VXLAN. For details about the Group Policy VXLAN, see the VXLAN Group Policy[8] document. Defaults to false.

    Added in version 224.

GenericProtocolExtension=
    Takes a boolean. When true, Generic Protocol Extension extends the existing VXLAN protocol to provide protocol typing, OAM, and versioning capabilities. For details about the VXLAN GPE Header, see the Generic Protocol Extension for VXLAN[9] document. If destination port is not specified and Generic Protocol Extension is set, the default port of 4790 is used. Defaults to false.

    Added in version 243.

DestinationPort=
    Configures the default destination UDP port. If the destination port is not specified, the Linux kernel default will be used. Set to 4789 to get the IANA assigned value.

    Added in version 229.

PortRange=
    Configures the source port range for the VXLAN. The kernel assigns the source UDP port based on the flow to help the receiver to do load balancing. When this option is not set, the normal range of local UDP ports is used.

    Added in version 229.

FlowLabel=
    Specifies the flow label to use in outgoing packets. The valid range is 0-1048575.

    Added in version 234.

IPDoNotFragment=
    Allows setting the IPv4 Do not Fragment (DF) bit in outgoing packets, or to inherit its value from the IPv4 inner header. Takes a boolean value, or "inherit". Set to "inherit" if the encapsulated protocol is IPv6. When unset, the kernel's default will be used.

    Added in version 243.

Independent=
    Takes a boolean. When true, the vxlan interface is created without any underlying network interface. Defaults to false, which means that a .network file that requests this VXLAN interface using VXLAN= is required for the VXLAN to be created.

    Added in version 247.

External=
    Takes a boolean. When true, the vxlan interface is externally controlled, for example by an EVPN control plane. Defaults to false.

    Added in version 258.

VNIFilter=
    Takes a boolean. When true, the interface is capable of filtering VNI filtering. Ignored if External= is set to false. Defaults to false.

    Added in version 258.

[GENEVE] SECTION OPTIONS

The [GENEVE] section only applies for netdevs of kind "geneve", and accepts the following keys:

Id=
    Specifies the Virtual Network Identifier (VNI) to use, a number between 0 and 16777215. This field is mandatory.

    Added in version 234.

Remote=
    Specifies the unicast destination IP address to use in outgoing packets.

    Added in version 234.

TOS=
    Specifies the TOS value to use in outgoing packets. Takes a number between 1 and 255.

    Added in version 234.

TTL=
    Accepts the same values as in the [VXLAN] section, except that when unset or set to 0, the kernel's default will be used, meaning that packet TTL will be set from /proc/sys/net/ipv4/ip_default_ttl.

    Added in version 234.

UDPChecksum=
    Takes a boolean. When true, specifies that UDP checksum is calculated for transmitted packets over IPv4.

    Added in version 234.

UDP6ZeroChecksumTx=
    Takes a boolean. When true, skip UDP checksum calculation for transmitted packets over IPv6.

    Added in version 234.

UDP6ZeroChecksumRx=
    Takes a boolean. When true, allows incoming UDP packets over IPv6 with zero checksum field.

    Added in version 234.

DestinationPort=
    Specifies destination port. Defaults to 6081. If not set or assigned the empty string, the default port of 6081 is used.

    Added in version 234.

FlowLabel=
    Specifies the flow label to use in outgoing packets.

    Added in version 234.

IPDoNotFragment=
    Accepts the same key as in [VXLAN] section.

    Added in version 243.

InheritInnerProtocol=
    Takes a boolean. When true, inner Layer 3 protocol is set as Protocol Type in the GENEVE header instead of Ethernet. Defaults to false.

    Added in version 254.

[HSR] SECTION OPTIONS

The [HSR] section only applies for netdevs of kind "hsr", and accepts the following keys:

Ports=
    Specifies the underlying interfaces. This field is mandatory and must contain exactly two interface names separated by space. This option can be specified multiples times, hence the two cases below have the same result:

        Ports=eth1 eth2

        Ports=eth1
        Ports=eth2

    All the previous assignments are cleared when an empty string is specified.

    Added in version 258.

Protocol=
    Specifies the protocol used by the interface. Takes one of "hsr" or "prp". Defaults to "hsr".

    Both protocols work by sending two copies of every outgoing frame, one for each of the two ports. The destination node receives the two frames and and keeps only the first one. If a link fails, only one of the two frames is received. HSR uses a ring topology where the two outgoing frames are sent in opposite directions in the ring. PRP doesn't need a specific topology, but it requires two completely redundant networks attached to the two ports.

    Added in version 258.

Supervision=
    Specifies the last byte of the destination MAC address of supervision frames. Takes a number between 0 and 255. Defaults to 0. Supervision frames are used by the HSR and the PRP protocols to monitor the integrity of the network and the presence of nodes. The first 5 bytes of the destination MAC are always 01:15:4E:00:01 while the last byte is configurable.

    Added in version 258.

[BAREUDP] SECTION OPTIONS

The [BareUDP] section only applies for netdevs of kind "bareudp", and accepts the following keys:

DestinationPort=
    Specifies the destination UDP port (in range 1...65535). This is mandatory.

    Added in version 247.

EtherType=
    Specifies the L3 protocol. Takes one of "ipv4", "ipv6", "mpls-uc" or "mpls-mc". This is mandatory.

    Added in version 247.

MinSourcePort=
    Specifies the lowest value of the UDP tunnel source port (in range 1...65535). Defaults to unset.

    Added in version 257.

[L2TP] SECTION OPTIONS

The [L2TP] section only applies for netdevs of kind "l2tp", and accepts the following keys:

TunnelId=
    Specifies the tunnel identifier. Takes a number in the range 1...4294967295. The value used must match the "PeerTunnelId=" value being used at the peer. This setting is compulsory.

    Added in version 242.

PeerTunnelId=
    Specifies the peer tunnel id. Takes a number in the range 1...4294967295. The value used must match the "TunnelId=" value being used at the peer. This setting is compulsory.

    Added in version 242.

Remote=
    Specifies the IP address of the remote peer. This setting is compulsory.

    Added in version 242.

Local=
    Specifies the IP address of a local interface. Takes an IP address, or the special values "auto", "static", or "dynamic". Optionally a name of a local interface can be specified after "@", e.g. "192.168.0.1@eth0" or "auto@eth0". When an address is specified, then a local or specified interface must have the address, and the remote address must be accessible through the local address. If "auto", then one of the addresses on a local or specified interface which is accessible to the remote address will be used. Similarly, if "static" or "dynamic" is set, then one of the static or dynamic addresses will be used. Defaults to "auto".

    Added in version 242.

EncapsulationType=
    Specifies the encapsulation type of the tunnel. Takes one of "udp" or "ip".

    Added in version 242.

UDPSourcePort=
    Specifies the UDP source port to be used for the tunnel. When UDP encapsulation is selected it is mandatory. Ignored when IP encapsulation is selected.

    Added in version 242.

UDPDestinationPort=
    Specifies destination port. When UDP encapsulation is selected it is mandatory. Ignored when IP encapsulation is selected.

    Added in version 245.

UDPChecksum=
    Takes a boolean. When true, specifies that UDP checksum is calculated for transmitted packets over IPv4.

    Added in version 242.

UDP6ChecksumTx=
    Takes a boolean. When true, skip UDP checksum calculation for transmitted packets over IPv6.

    Added in version 242.

UDP6ChecksumRx=
    Takes a boolean. When true, allows incoming UDP packets over IPv6 with zero checksum field.

    Added in version 242.

[L2TPSESSION] SECTION OPTIONS

The [L2TPSession] section only applies for netdevs of kind "l2tp", and accepts the following keys:

Name=
    Specifies the name of the session. This setting is compulsory.

    Added in version 242.

SessionId=
    Specifies the session identifier. Takes a number in the range 1...4294967295. The value used must match the "SessionId=" value being used at the peer. This setting is compulsory.

    Added in version 242.

PeerSessionId=
    Specifies the peer session identifier. Takes a number in the range 1...4294967295. The value used must match the "PeerSessionId=" value being used at the peer. This setting is compulsory.

    Added in version 242.

Layer2SpecificHeader=
    Specifies layer2specific header type of the session. One of "none" or "default". Defaults to "default".

    Added in version 242.

[MACSEC] SECTION OPTIONS

The [MACsec] section only applies for network devices of kind "macsec", and accepts the following keys:

Port=
    Specifies the port to be used for the MACsec transmit channel. The port is used to make secure channel identifier (SCI). Takes a value between 1 and 65535. Defaults to unset.

    Added in version 243.

Encrypt=
    Takes a boolean. When true, enable encryption. Defaults to unset.

    Added in version 243.

[MACSECRECEIVECHANNEL] SECTION OPTIONS

The [MACsecReceiveChannel] section only applies for network devices of kind "macsec", and accepts the following keys:

Port=
    Specifies the port to be used for the MACsec receive channel. The port is used to make secure channel identifier (SCI). Takes a value between 1 and 65535. This option is compulsory, and is not set by default.

    Added in version 243.

MACAddress=
    Specifies the MAC address to be used for the MACsec receive channel. The MAC address used to make secure channel identifier (SCI). This setting is compulsory, and is not set by default.

    Added in version 243.

[MACSECTRANSMITASSOCIATION] SECTION OPTIONS

The [MACsecTransmitAssociation] section only applies for network devices of kind "macsec", and accepts the following keys:

PacketNumber=
    Specifies the packet number to be used for replay protection and the construction of the initialization vector (along with the secure channel identifier [SCI]). Takes a value between 1-4,294,967,295. Defaults to unset.

    Added in version 243.

KeyId=
    Specifies the identification for the key. Takes a number between 0-255. This option is compulsory, and is not set by default.

    Added in version 243.

Key=
    Specifies the encryption key used in the transmission channel. The same key must be configured on the peer’s matching receive channel. This setting is compulsory, and is not set by default. Takes a 128-bit key encoded in a hexadecimal string, for example "dffafc8d7b9a43d5b9a3dfbbf6a30c16".

    Added in version 243.

KeyFile=
    Takes an absolute path to a file which contains a 128-bit key encoded in a hexadecimal string, which will be used in the transmission channel. When this option is specified, Key= is ignored. Note that the file must be readable by the user "systemd-network", so it should be, e.g., owned by "root:systemd-network" with a "0640" file mode. If the path refers to an AF_UNIX stream socket in the file system a connection is made to it and the key read from it.

    Added in version 243.

Activate=
    Takes a boolean. If enabled, then the security association is activated. Defaults to unset.

    Added in version 243.

UseForEncoding=
    Takes a boolean. If enabled, then the security association is used for encoding. Only one [MACsecTransmitAssociation] section can enable this option. When enabled, Activate=yes is implied. Defaults to unset.

    Added in version 243.

[MACSECRECEIVEASSOCIATION] SECTION OPTIONS

The [MACsecReceiveAssociation] section only applies for network devices of kind "macsec", and accepts the following keys:

Port=
    Accepts the same key as in [MACsecReceiveChannel] section.

    Added in version 243.

MACAddress=
    Accepts the same key as in [MACsecReceiveChannel] section.

    Added in version 243.

PacketNumber=
    Accepts the same key as in [MACsecTransmitAssociation] section.

    Added in version 243.

KeyId=
    Accepts the same key as in [MACsecTransmitAssociation] section.

    Added in version 243.

Key=
    Accepts the same key as in [MACsecTransmitAssociation] section.

    Added in version 243.

KeyFile=
    Accepts the same key as in [MACsecTransmitAssociation] section.

    Added in version 243.

Activate=
    Accepts the same key as in [MACsecTransmitAssociation] section.

    Added in version 243.

[TUNNEL] SECTION OPTIONS

The [Tunnel] section only applies for netdevs of kind "ipip", "sit", "gre", "gretap", "ip6gre", "ip6gretap", "vti", "vti6", "ip6tnl", and "erspan" and accepts the following keys:

External=
    Takes a boolean value. When true, then the tunnel is externally controlled, which is also known as collect metadata mode, and most settings below like Local= or Remote= are ignored. This implies Independent=. Defaults to false.

    Added in version 251.

Local=
    A static local address for tunneled packets. It must be an address on another interface of this host, or one of the special values "any", "ipv4_link_local", "ipv6_link_local", "dhcp4", "dhcp6", "dhcp_pd", and "slaac". If one of the special values except for "any" is specified, an address which matches the corresponding type on the underlying interface will be used. Defaults to "any".

    Added in version 215.

Remote=
    The remote endpoint of the tunnel. Takes an IP address or the special value "any".

    Added in version 215.

TOS=
    The Type Of Service byte value for a tunnel interface. For details about the TOS, see the Type of Service in the Internet Protocol Suite[10] document.

    Added in version 215.

TTL=
    A fixed Time To Live N on tunneled packets. N is a number in the range 1...255. 0 is a special value meaning that packets inherit the TTL value. The default value for IPv4 tunnels is 0 (inherit). The default value for IPv6 tunnels is 64.

    Added in version 215.

DiscoverPathMTU=
    Takes a boolean. When true, enables Path MTU Discovery on the tunnel. When IgnoreDontFragment= is enabled, defaults to false. Otherwise, defaults to true.

    Added in version 215.

IgnoreDontFragment=
    Takes a boolean. When true, enables IPv4 Don't Fragment (DF) suppression on the tunnel. Defaults to false. Note that if IgnoreDontFragment= is set to true, DiscoverPathMTU= cannot be set to true. Only applicable to GRE, GRETAP, and ERSPAN tunnels.

    Added in version 254.

IPv6FlowLabel=
    Configures the 20-bit flow label (see RFC 6437[11]) field in the IPv6 header (see RFC 2460[12]), which is used by a node to label packets of a flow. It is only used for IPv6 tunnels. A flow label of zero is used to indicate packets that have not been labeled. It can be configured to a value in the range 0...0xFFFFF, or be set to "inherit", in which case the original flowlabel is used.

    Added in version 223.

CopyDSCP=
    Takes a boolean. When true, the Differentiated Service Code Point (DSCP) field will be copied to the inner header from outer header during the decapsulation of an IPv6 tunnel packet. DSCP is a field in an IP packet that enables different levels of service to be assigned to network traffic. Defaults to "no".

    Added in version 223.

EncapsulationLimit=
    The Tunnel Encapsulation Limit option specifies how many additional levels of encapsulation are permitted to be prepended to the packet. For example, a Tunnel Encapsulation Limit option containing a limit value of zero means that a packet carrying that option may not enter another tunnel before exiting the current tunnel. (see RFC 2473[13]). The valid range is 0...255 and "none". Defaults to 4.

    Added in version 226.

Key=
    The Key= parameter specifies the same key to use in both directions (InputKey= and OutputKey=). The Key= is either a number or an IPv4 address-like dotted quad. It is used as mark-configured SAD/SPD entry as part of the lookup key (both in data and control path) in IP XFRM (framework used to implement IPsec protocol). See ip-xfrm — transform configuration[14] for details. It is only used for VTI/VTI6, GRE, GRETAP, and ERSPAN tunnels.

    Added in version 231.

InputKey=
    The InputKey= parameter specifies the key to use for input. The format is same as Key=. It is only used for VTI/VTI6, GRE, GRETAP, and ERSPAN tunnels.

    Added in version 231.

OutputKey=
    The OutputKey= parameter specifies the key to use for output. The format is same as Key=. It is only used for VTI/VTI6, GRE, GRETAP, and ERSPAN tunnels.

    Added in version 231.

Mode=
    Specifies the tunnel mode. Acceptable values depend on the tunnel kind.

    Table 2. Supported tunnel modes
    Kind | Mode | Description
    "ipip" | "ipip" | IPv4 over IPv4 (default)
     | "any" | both IPv4 and IPv6 over IPv4
    "sit" | "ipip" | IPv4 over IPv4
     | "ip6ip" | IPv6 over IPv4 (default)
     | "any" | both IPv4 and IPv6 over IPv4
    "ip6tnl" | "ipip6" | IPv4 over IPv6
     | "ip6ip6" | IPv6 over IPv6
     | "any" | both IPv4 and IPv6 over IPv6 (default)

    Added in version 219.

Independent=
    Takes a boolean. When false (the default), the tunnel is always created over some network device, and a .network file that requests this tunnel using Tunnel= is required for the tunnel to be created. When true, the tunnel is created independently of any network as "tunnel@NONE".

    Added in version 235.

AssignToLoopback=
    Takes a boolean. If set to "yes", the loopback interface "lo" is used as the underlying device of the tunnel interface. Defaults to "no".

    Added in version 243.

AllowLocalRemote=
    Takes a boolean. When true allows tunnel traffic on ip6tnl devices where the remote endpoint is a local host address. When unset, the kernel's default will be used.

    Added in version 237.

FooOverUDP=
    Takes a boolean. Specifies whether FooOverUDP= tunnel is to be configured. Defaults to false. This takes effects only for IPIP, SIT, GRE, and GRETAP tunnels. For more detail information see Foo over UDP[15]

    Added in version 240.

FOUDestinationPort=
    This setting specifies the UDP destination port for encapsulation. This field is mandatory when FooOverUDP=yes, and is not set by default.

    Added in version 240.

FOUSourcePort=
    This setting specifies the UDP source port for encapsulation. Defaults to 0 — that is, the source port for packets is left to the network stack to decide.

    Added in version 240.

Encapsulation=
    Accepts the same key as in the [FooOverUDP] section.

    Added in version 240.

IPv6RapidDeploymentPrefix=
    Reconfigure the tunnel for IPv6 Rapid Deployment[16], also known as 6rd. The value is an ISP-specific IPv6 prefix with a non-zero length. Only applicable to SIT tunnels.

    Added in version 240.

ISATAP=
    Takes a boolean. If set, configures the tunnel as Intra-Site Automatic Tunnel Addressing Protocol (ISATAP) tunnel. Only applicable to SIT tunnels. When unset, the kernel's default will be used.

    Added in version 240.

SerializeTunneledPackets=
    Takes a boolean. If set to yes, then packets are serialized. Only applies for GRE, GRETAP, and ERSPAN tunnels. When unset, the kernel's default will be used.

    Added in version 240.

ERSPANVersion=
    Specifies the ERSPAN version number. Takes 0 for version 0 (a.k.a. type I), 1 for version 1 (a.k.a. type II), or 2 for version 2 (a.k.a. type III). Defaults to 1.

    Added in version 252.

ERSPANIndex=
    Specifies the ERSPAN v1 index field for the interface. Takes an integer in the range 0...1048575, which is associated with the ERSPAN traffic's source port and direction. Only used when ERSPANVersion=1. Defaults to 0.

    Added in version 240.

ERSPANDirection=
    Specifies the ERSPAN v2 mirrored traffic's direction. Takes "ingress" or "egress". Only used when ERSPANVersion=2. Defaults to "ingress".

    Added in version 252.

ERSPANHardwareId=
    Specifies a unique identifier of the ERSPAN v2 engine. Takes an integer in the range 0...63. Only used when ERSPANVersion=2. Defaults to 0.

    Added in version 252.

[FOOOVERUDP] SECTION OPTIONS

The [FooOverUDP] section only applies for netdevs of kind "fou" and accepts the following keys:

Encapsulation=
    Specifies the encapsulation mechanism used to store networking packets of various protocols inside the UDP packets. Supports the following values: "FooOverUDP" provides the simplest no-frills model of UDP encapsulation, it simply encapsulates packets directly in the UDP payload. "GenericUDPEncapsulation" is a generic and extensible encapsulation, it allows encapsulation of packets for any IP protocol and optional data as part of the encapsulation. For more detailed information see Generic UDP Encapsulation[17]. Defaults to "FooOverUDP".

    Added in version 240.

Port=
    Specifies the port number where the encapsulated packets will arrive. Those packets will be removed and manually fed back into the network stack with the encapsulation removed to be sent to the real destination. This option is mandatory.

    Added in version 240.

PeerPort=
    Specifies the peer port number. Defaults to unset. Note that when peer port is set "Peer=" address is mandatory.

    Added in version 243.

Protocol=
    The Protocol= specifies the protocol number of the packets arriving at the UDP port. When Encapsulation=FooOverUDP, this field is mandatory and is not set by default. Takes an IP protocol name such as "gre" or "ipip", or an integer within the range 1...255. When Encapsulation=GenericUDPEncapsulation, this must not be specified.

    Added in version 240.

Peer=
    Configures peer IP address. Note that when peer address is set "PeerPort=" is mandatory.

    Added in version 243.

Local=
    Configures local IP address.

    Added in version 243.

[PEER] SECTION OPTIONS

The [Peer] section only applies for netdevs of kind "veth" and accepts the following keys:

Name=
    The interface name used when creating the netdev. This setting is compulsory.

    Added in version 215.

MACAddress=
    The peer MACAddress, if not set, it is generated in the same way as the MAC address of the main interface.

    Added in version 215.

[VXCAN] SECTION OPTIONS

The [VXCAN] section only applies for netdevs of kind "vxcan" and accepts the following key:

Peer=
    The peer interface name used when creating the netdev. This setting is compulsory.

    Added in version 236.

[TUN] SECTION OPTIONS

The [Tun] section only applies for netdevs of kind "tun", and accepts the following keys:

MultiQueue=
    Takes a boolean. Configures whether to use multiple file descriptors (queues) to parallelize packets sending and receiving. Defaults to "no".

    Added in version 215.

PacketInfo=
    Takes a boolean. Configures whether packets should be prepended with four extra bytes (two flag bytes and two protocol bytes). If disabled, it indicates that the packets will be pure IP packets. Defaults to "no".

    Added in version 215.

VNetHeader=
    Takes a boolean. Configures IFF_VNET_HDR flag for a tun or tap device. It allows sending and receiving larger Generic Segmentation Offload (GSO) packets. This may increase throughput significantly. Defaults to "no".

    Added in version 223.

User=
    User to grant access to the /dev/net/tun device. The specified user must be a system user.

    Added in version 215.

Group=
    Group to grant access to the /dev/net/tun device. The specified group must be a system group.

    Added in version 215.

KeepCarrier=
    Takes a boolean. If enabled, to make the interface maintain its carrier status, the file descriptor of the interface is kept open. This may be useful to keep the interface in running state, for example while the backing process is temporarily shutdown. Defaults to "no".

    Added in version 252.

[TAP] SECTION OPTIONS

The [Tap] section only applies for netdevs of kind "tap", and accepts the same keys as the [Tun] section.

[WIREGUARD] SECTION OPTIONS

The [WireGuard] section accepts the following keys:

PrivateKey=
    The Base64 encoded private key for the interface. It can be generated using the wg genkey command (see wg(8)). Specially, if the specified key is prefixed with "@", it is interpreted as the name of the credential from which the actual key shall be read. systemd-networkd.service(8) automatically imports credentials matching "network.wireguard.*". For more details on credentials, refer to systemd.exec(5). A private key is mandatory to use WireGuard. If not set, the credential "network.wireguard.private.netdev" is used if exists. I.e. for 50-foobar.netdev, "network.wireguard.private.50-foobar" is tried.

    Note that because this information is secret, it is strongly recommended to use an (encrypted) credential. Alternatively, you may want to set the permissions of the .netdev file to be owned by "root:systemd-network" with a "0640" file mode.

    Added in version 237.

PrivateKeyFile=
    Takes an absolute path to a file which contains the Base64 encoded private key for the interface. When this option is specified, then PrivateKey= is ignored. Note that the file must be readable by the user "systemd-network", so it should be, e.g., owned by "root:systemd-network" with a "0640" file mode. If the path refers to an AF_UNIX stream socket in the file system a connection is made to it and the key read from it.

    Added in version 242.

ListenPort=
    Sets UDP port for listening. Takes either value between 1 and 65535 or "auto". If "auto" is specified, the port is automatically generated based on interface name. Defaults to "auto".

    Added in version 237.

FirewallMark=
    Sets a firewall mark on outgoing WireGuard packets from this interface. Takes a number between 1 and 4294967295.

    Added in version 243.

RouteTable=
    The table identifier for the routes to the addresses specified in the AllowedIPs=. Takes a negative boolean value, one of the predefined names "default", "main", and "local", names defined in RouteTable= in networkd.conf(5), or a number in the range 1...4294967295. When "off" the routes to the addresses specified in the AllowedIPs= setting will not be configured. Defaults to false. This setting will be ignored when the same setting is specified in the [WireGuardPeer] section.

    Added in version 250.

RouteMetric=
    The priority of the routes to the addresses specified in the AllowedIPs=. Takes an integer in the range 0...4294967295. Defaults to 0 for IPv4 addresses, and 1024 for IPv6 addresses. This setting will be ignored when the same setting is specified in the [WireGuardPeer] section.

    Added in version 250.

[WIREGUARDPEER] SECTION OPTIONS

The [WireGuardPeer] section accepts the following keys:

PublicKey=
    Sets a Base64 encoded public key calculated by wg pubkey (see wg(8)) from a private key, and usually transmitted out of band to the author of the configuration file. This option honors the "@" prefix in the same way as the PrivateKey= setting of the [WireGuard] section. This option is mandatory for this section.

    Added in version 237.

PublicKeyFile=
    Takes an absolute path to a file which contains the Base64 encoded public key for the peer. When this option is specified, then PublicKey= will be ignored. Note that the file must be readable by the user "systemd-network", so it should be, e.g., owned by "root:systemd-network" with a "0640" file mode. If the path refers to an AF_UNIX stream socket in the file system a connection is made to it and the key read from it.

    Added in version 257.

PresharedKey=
    Optional preshared key for the interface. It can be generated by the wg genpsk command. This option adds an additional layer of symmetric-key cryptography to be mixed into the already existing public-key cryptography, for post-quantum resistance. This option honors the "@" prefix in the same way as the PrivateKey= setting of the [WireGuard] section.

    Note that because this information is secret, it is strongly recommended to use an (encrypted) credential. Alternatively, you may want to set the permissions of the .netdev file to be owned by "root:systemd-network" with a "0640" file mode.

    Added in version 237.

PresharedKeyFile=
    Takes an absolute path to a file which contains the Base64 encoded preshared key for the peer. When this option is specified, then PresharedKey= is ignored. Note that the file must be readable by the user "systemd-network", so it should be, e.g., owned by "root:systemd-network" with a "0640" file mode. If the path refers to an AF_UNIX stream socket in the file system a connection is made to it and the key read from it.

    Added in version 242.

AllowedIPs=
    Sets a comma-separated list of IP (v4 or v6) addresses with CIDR masks from which this peer is allowed to send incoming traffic and to which outgoing traffic for this peer is directed. This setting can be specified multiple times. If an empty string is assigned, then the all previous assignments are cleared.

    The catch-all 0.0.0.0/0 may be specified for matching all IPv4 addresses, and ::/0 may be specified for matching all IPv6 addresses.

    Note that this only affects routing inside the network interface itself, i.e. the packets that pass through the tunnel itself. To cause packets to be sent via the tunnel in the first place, an appropriate route needs to be added as well — either in the "[Routes]" section on the ".network" matching the wireguard interface, or externally to systemd-networkd.

    Added in version 237.

Endpoint=
    Sets an endpoint IP address or hostname, followed by a colon, and then a port number. IPv6 address must be in the square brackets. For example, "111.222.333.444:51820" for IPv4 and "[1111:2222::3333]:51820" for IPv6 address. This endpoint will be updated automatically once to the most recent source IP address and port of correctly authenticated packets from the peer at configuration time.

    This option honors the "@" prefix in the same way as the PrivateKey= setting of the [WireGuard] section.

    Added in version 237.

PersistentKeepalive=
    Sets a seconds interval, between 1 and 65535 inclusive, of how often to send an authenticated empty packet to the peer for the purpose of keeping a stateful firewall or NAT mapping valid persistently. For example, if the interface very rarely sends traffic, but it might at anytime receive traffic from a peer, and it is behind NAT, the interface might benefit from having a persistent keepalive interval of 25 seconds. If set to 0 or "off", this option is disabled. By default or when unspecified, this option is off. Most users will not need this.

    Added in version 237.

RouteTable=
    The table identifier for the routes to the addresses specified in the AllowedIPs=. Takes a negative boolean value, one of the predefined names "default", "main", and "local", names defined in RouteTable= in networkd.conf(5), or a number in the range 1...4294967295. Defaults to unset, and the value specified in the same setting in the [WireGuard] section will be used.

    Added in version 250.

RouteMetric=
    The priority of the routes to the addresses specified in the AllowedIPs=. Takes an integer in the range 0...4294967295. Defaults to unset, and the value specified in the same setting in the [WireGuard] section will be used.

    Added in version 250.

[BOND] SECTION OPTIONS

The [Bond] section accepts the following key:

Mode=
    Specifies one of the bonding policies. The default is "balance-rr" (round robin). Possible values are "balance-rr", "active-backup", "balance-xor", "broadcast", "802.3ad", "balance-tlb", and "balance-alb".

    Added in version 216.

TransmitHashPolicy=
    Selects the transmit hash policy to use for slave selection in balance-xor, 802.3ad, and tlb modes. Possible values are "layer2", "layer3+4", "layer2+3", "encap2+3", and "encap3+4".

    Added in version 216.

LACPTransmitRate=
    Specifies the rate with which link partner transmits Link Aggregation Control Protocol Data Unit packets in 802.3ad mode. Possible values are "slow", which requests partner to transmit LACPDUs every 30 seconds, and "fast", which requests partner to transmit LACPDUs every second. The default value is "slow".

    Added in version 216.

MIIMonitorSec=
    Specifies the frequency that Media Independent Interface link monitoring will occur. A value of zero disables MII link monitoring. This value is rounded down to the nearest millisecond. The default value is 0.

    Added in version 216.

PeerNotifyDelaySec=
    Specifies the number of seconds the delay between each peer notification (gratuitous ARP and unsolicited IPv6 Neighbor Advertisement) when they are issued after a failover event. This delay should be a multiple of the MII link monitor interval (miimon). The valid range is 0...300s. The default value is 0, which means to match the value of the MIIMonitorSec=.

    Added in version 256.

UpDelaySec=
    Specifies the delay before a link is enabled after a link up status has been detected. This value is rounded down to a multiple of MIIMonitorSec=. The default value is 0.

    Added in version 216.

DownDelaySec=
    Specifies the delay before a link is disabled after a link down status has been detected. This value is rounded down to a multiple of MIIMonitorSec=. The default value is 0.

    Added in version 216.

LearnPacketIntervalSec=
    Specifies the number of seconds between instances where the bonding driver sends learning packets to each slave peer switch. The valid range is 1...0x7fffffff; the default value is 1. This option has an effect only for the balance-tlb and balance-alb modes.

    Added in version 220.

AdSelect=
    Specifies the 802.3ad aggregation selection logic to use. Possible values are "stable", "bandwidth" and "count".

    Added in version 220.

AdActorSystemPriority=
    Specifies the 802.3ad actor system priority. Takes a number in the range 1...65535.

    Added in version 240.

AdUserPortKey=
    Specifies the 802.3ad user defined portion of the port key. Takes a number in the range 0...1023.

    Added in version 240.

AdActorSystem=
    Specifies the 802.3ad system MAC address. This cannot be a null or multicast address.

    Added in version 240.

FailOverMACPolicy=
    Specifies whether the active-backup mode should set all slaves to the same MAC address at the time of enslavement or, when enabled, to perform special handling of the bond's MAC address in accordance with the selected policy. The default policy is none. Possible values are "none", "active" and "follow".

    Added in version 220.

ARPValidate=
    Specifies whether or not ARP probes and replies should be validated in any mode that supports ARP monitoring, or whether non-ARP traffic should be filtered (disregarded) for link monitoring purposes. Possible values are "none", "active", "backup" and "all".

    Added in version 220.

ARPIntervalSec=
    Specifies the ARP link monitoring frequency. A value of 0 disables ARP monitoring. The default value is 0, and the default unit seconds.

    Added in version 220.

ARPIPTargets=
    Specifies the IP addresses to use as ARP monitoring peers when ARPIntervalSec= is greater than 0. These are the targets of the ARP request sent to determine the health of the link to the targets. Specify these values in IPv4 dotted decimal format. At least one IP address must be given for ARP monitoring to function. The maximum number of targets that can be specified is 16. The default value is no IP addresses.

    Added in version 220.

ARPAllTargets=
    Specifies the quantity of ARPIPTargets= that must be reachable in order for the ARP monitor to consider a slave as being up. This option affects only active-backup mode for slaves with ARPValidate enabled. Possible values are "any" and "all".

    Added in version 220.

PrimaryReselectPolicy=
    Specifies the reselection policy for the primary slave. This affects how the primary slave is chosen to become the active slave when failure of the active slave or recovery of the primary slave occurs. This option is designed to prevent flip-flopping between the primary slave and other slaves. Possible values are "always", "better" and "failure".

    Added in version 220.

ResendIGMP=
    Specifies the number of IGMP membership reports to be issued after a failover event. One membership report is issued immediately after the failover, subsequent packets are sent in each 200ms interval. The valid range is 0...255. Defaults to 1. A value of 0 prevents the IGMP membership report from being issued in response to the failover event.

    Added in version 220.

PacketsPerSlave=
    Specify the number of packets to transmit through a slave before moving to the next one. When set to 0, then a slave is chosen at random. The valid range is 0...65535. Defaults to 1. This option only has effect when in balance-rr mode.

    Added in version 220.

GratuitousARP=
    Specify the number of peer notifications (gratuitous ARPs and unsolicited IPv6 Neighbor Advertisements) to be issued after a failover event. As soon as the link is up on the new slave, a peer notification is sent on the bonding device and each VLAN sub-device. This is repeated at each link monitor interval (ARPIntervalSec or MIIMonitorSec, whichever is active) if the number is greater than 1. The valid range is 0...255. The default value is 1. These options affect only the active-backup mode.

    Added in version 220.

AllSlavesActive=
    Takes a boolean. Specifies that duplicate frames (received on inactive ports) should be dropped when false, or delivered when true. Normally, bonding will drop duplicate frames (received on inactive ports), which is desirable for most users. But there are some cases where it is nice to allow duplicate frames to be delivered. The default value is false (drop duplicate frames received on inactive ports).

    Added in version 220.

DynamicTransmitLoadBalancing=
    Takes a boolean. Specifies if dynamic shuffling of flows is enabled. Applies only for balance-tlb mode. Defaults to unset.

    Added in version 240.

MinLinks=
    Specifies the minimum number of links that must be active before asserting carrier. The default value is 0.

    Added in version 220.

ARPMissedMax=
    Specify the maximum number of arp interval monitor cycle for missed ARP replies. If this number is exceeded, link is reported as down. Defaults to unset.

    Added in version 256.

For more detail information see Linux Ethernet Bonding Driver HOWTO[1]

[XFRM] SECTION OPTIONS

The [Xfrm] section accepts the following keys:

InterfaceId=
    Sets the ID/key of the xfrm interface which needs to be associated with a SA/policy. Can be decimal or hexadecimal, valid range is 1-0xffffffff. This is mandatory.

    Added in version 243.

Independent=
    Takes a boolean. If false (the default), the xfrm interface must have an underlying device which can be used for hardware offloading.

    Added in version 243.

For more detail information see Virtual XFRM Interfaces[18].

[VRF] SECTION OPTIONS

The [VRF] section only applies for netdevs of kind "vrf" and accepts the following key:

Table=
    The numeric routing table identifier. This setting is compulsory.

    Added in version 243.

[BATMANADVANCED] SECTION OPTIONS

The [BatmanAdvanced] section only applies for netdevs of kind "batadv" and accepts the following keys:

GatewayMode=
    Takes one of "off", "server", or "client". A batman-adv node can either run in server mode (sharing its internet connection with the mesh) or in client mode (searching for the most suitable internet connection in the mesh) or having the gateway support turned off entirely (which is the default setting).

    Added in version 248.

Aggregation=
    Takes a boolean value. Enables or disables aggregation of originator messages. Defaults to true.

    Added in version 248.

BridgeLoopAvoidance=
    Takes a boolean value. Enables or disables avoidance of loops on bridges. Defaults to true.

    Added in version 248.

DistributedArpTable=
    Takes a boolean value. Enables or disables the distributed ARP table. Defaults to true.

    Added in version 248.

Fragmentation=
    Takes a boolean value. Enables or disables fragmentation. Defaults to true.

    Added in version 248.

HopPenalty=
    The hop penalty setting allows one to modify batctl(8) preference for multihop routes vs. short routes. This integer value is applied to the TQ (Transmit Quality) of each forwarded OGM (Originator Message), thereby propagating the cost of an extra hop (the packet has to be received and retransmitted which costs airtime). A higher hop penalty will make it more unlikely that other nodes will choose this node as intermediate hop towards any given destination. The default hop penalty of '15' is a reasonable value for most setups and probably does not need to be changed. However, mobile nodes could choose a value of 255 (maximum value) to avoid being chosen as a router by other nodes. The minimum value is 0.

    Added in version 248.

OriginatorIntervalSec=
    The value specifies the interval in seconds, unless another time unit is specified in which batman-adv floods the network with its protocol information. See systemd.time(7) for more information.

    Added in version 248.

GatewayBandwidthDown=
    If the node is a server, this parameter is used to inform other nodes in the network about this node's internet connection download bandwidth in bits per second. Just enter any number suffixed with K, M, G or T (base 1000) and the batman-adv module will propagate the entered value in the mesh.

    Added in version 248.

GatewayBandwidthUp=
    If the node is a server, this parameter is used to inform other nodes in the network about this node's internet connection upload bandwidth in bits per second. Just enter any number suffixed with K, M, G or T (base 1000) and the batman-adv module will propagate the entered value in the mesh.

    Added in version 248.

RoutingAlgorithm=
    This can be either "batman-v" or "batman-iv" and describes which routing_algo of batctl(8) to use. The algorithm cannot be changed after interface creation. Defaults to "batman-v".

    Added in version 248.

[IPOIB] SECTION OPTIONS

The [IPoIB] section only applies for netdevs of kind "ipoib" and accepts the following keys:

PartitionKey=
    Takes an integer in the range 1...0xffff, except for 0x8000. Defaults to unset, and the kernel's default is used.

    Added in version 250.

Mode=
    Takes one of the special values "datagram" or "connected". Defaults to unset, and the kernel's default is used.

    When "datagram", the Infiniband unreliable datagram (UD) transport is used, and so the interface MTU is equal to the IB L2 MTU minus the IPoIB encapsulation header (4 bytes). For example, in a typical IB fabric with a 2K MTU, the IPoIB MTU will be 2048 - 4 = 2044 bytes.

    When "connected", the Infiniband reliable connected (RC) transport is used. Connected mode takes advantage of the connected nature of the IB transport and allows an MTU up to the maximal IP packet size of 64K, which reduces the number of IP packets needed for handling large UDP datagrams, TCP segments, etc and increases the performance for large messages.

    Added in version 250.

IgnoreUserspaceMulticastGroups=
    Takes a boolean value. When true, the kernel ignores multicast groups handled by userspace. Defaults to unset, and the kernel's default is used.

    Added in version 250.

[WLAN] SECTION OPTIONS

The [WLAN] section only applies to WLAN interfaces, and accepts the following keys:

PhysicalDevice=
    Specifies the name or index of the physical WLAN device (e.g. "0" or "phy0"). The list of the physical WLAN devices that exist on the host can be obtained by iw phy command. This option is mandatory.

    Added in version 251.

Type=
    Specifies the type of the interface. Takes one of the "ad-hoc", "station", "ap", "ap-vlan", "wds", "monitor", "mesh-point", "p2p-client", "p2p-go", "p2p-device", "ocb", and "nan". This option is mandatory.

    Added in version 251.

WDS=
    Enables the Wireless Distribution System (WDS) mode on the interface. The mode is also known as the "4 address mode". Takes a boolean value. Defaults to unset, and the kernel's default will be used.

    Added in version 251.

EXAMPLES

Example 1. /etc/systemd/network/25-bridge.netdev

    [NetDev]
    Name=bridge0
    Kind=bridge

Example 2. /etc/systemd/network/25-vlan1.netdev

    [Match]
    Virtualization=no
    [NetDev]
    Name=vlan1
    Kind=vlan
    [VLAN]
    Id=1

Example 3. /etc/systemd/network/25-ipip.netdev

    [NetDev]
    Name=ipip-tun
    Kind=ipip
    MTUBytes=1480
    [Tunnel]
    Local=192.168.223.238
    Remote=192.169.224.239
    TTL=64

Example 4. /etc/systemd/network/1-fou-tunnel.netdev

    [NetDev]
    Name=fou-tun
    Kind=fou
    [FooOverUDP]
    Port=5555
    Protocol=4

Example 5. /etc/systemd/network/25-fou-ipip.netdev

    [NetDev]
    Name=ipip-tun
    Kind=ipip
    [Tunnel]
    Independent=yes
    Local=10.65.208.212
    Remote=10.65.208.211
    FooOverUDP=yes
    FOUDestinationPort=5555

Example 6. /etc/systemd/network/25-tap.netdev

    [NetDev]
    Name=tap-test
    Kind=tap
    [Tap]
    MultiQueue=yes
    PacketInfo=yes

Example 7. /etc/systemd/network/25-sit.netdev

    [NetDev]
    Name=sit-tun
    Kind=sit
    MTUBytes=1480
    [Tunnel]
    Local=10.65.223.238
    Remote=10.65.223.239

Example 8. /etc/systemd/network/25-6rd.netdev

    [NetDev]
    Name=6rd-tun
    Kind=sit
    MTUBytes=1480
    [Tunnel]
    Local=10.65.223.238
    IPv6RapidDeploymentPrefix=2602::/24

Example 9. /etc/systemd/network/25-gre.netdev

    [NetDev]
    Name=gre-tun
    Kind=gre
    MTUBytes=1480
    [Tunnel]
    Local=10.65.223.238
    Remote=10.65.223.239

Example 10. /etc/systemd/network/25-ip6gre.netdev

    [NetDev]
    Name=ip6gre-tun
    Kind=ip6gre
    [Tunnel]
    Key=123

Example 11. /etc/systemd/network/25-vti.netdev

    [NetDev]
    Name=vti-tun
    Kind=vti
    MTUBytes=1480
    [Tunnel]
    Local=10.65.223.238
    Remote=10.65.223.239

Example 12. /etc/systemd/network/25-veth.netdev

    [NetDev]
    Name=veth-test
    Kind=veth
    [Peer]
    Name=veth-peer

Example 13. /etc/systemd/network/25-bond.netdev

    [NetDev]
    Name=bond1
    Kind=bond
    [Bond]
    Mode=802.3ad
    TransmitHashPolicy=layer3+4
    MIIMonitorSec=1s
    LACPTransmitRate=fast

Example 14. /etc/systemd/network/25-dummy.netdev

    [NetDev]
    Name=dummy-test
    Kind=dummy
    MACAddress=12:34:56:78:9a:bc

Example 15. /etc/systemd/network/25-vrf.netdev

Create a VRF interface with table 42.

    [NetDev]
    Name=vrf-test
    Kind=vrf
    [VRF]
    Table=42

Example 16. /etc/systemd/network/25-macvtap.netdev

Create a MacVTap device.

    [NetDev]
    Name=macvtap-test
    Kind=macvtap

Example 17. /etc/systemd/network/25-wireguard.netdev

    [NetDev]
    Name=wg0
    Kind=wireguard
    [WireGuard]
    PrivateKey=EEGlnEPYJV//kbvvIqxKkQwOiS+UENyPncC4bF46ong=
    ListenPort=51820
    [WireGuardPeer]
    PublicKey=RDf+LSpeEre7YEIKaxg+wbpsNV7du+ktR99uBEtIiCA=
    AllowedIPs=fd31:bf08:57cb::/48,192.168.26.0/24
    Endpoint=wireguard.example.com:51820

Example 18. /etc/systemd/network/27-xfrm.netdev

    [NetDev]
    Name=xfrm0
    Kind=xfrm
    [Xfrm]
    Independent=yes

SEE ALSO

systemd(1), systemd-networkd.service(8), systemd.link(5), systemd.network(5), systemd-network-generator.service(8)

NOTES

1.  Linux Ethernet Bonding Driver HOWTO
    https://docs.kernel.org/networking/bonding.html

2.  RFC 2784
    https://tools.ietf.org/html/rfc2784

3.  IEEE 802.1Q
    http://www.ieee802.org/1/pages/802.1Q.html

4.  VRF
    https://docs.kernel.org/networking/vrf.html

5.  B.A.T.M.A.N. Advanced
    https://www.open-mesh.org/projects/open-mesh/wiki

6.  System and Service Credentials
    https://systemd.io/CREDENTIALS

7.  Distributed Overlay Virtual Ethernet (DOVE)
    https://en.wikipedia.org/wiki/Distributed_Overlay_Virtual_Ethernet

8.  VXLAN Group Policy
    https://tools.ietf.org/html/draft-smith-vxlan-group-policy

9.  Generic Protocol Extension for VXLAN
    https://tools.ietf.org/html/draft-ietf-nvo3-vxlan-gpe-07

10. Type of Service in the Internet Protocol Suite
    http://tools.ietf.org/html/rfc1349

11. RFC 6437
    https://tools.ietf.org/html/rfc6437

12. RFC 2460
    https://tools.ietf.org/html/rfc2460

13. RFC 2473
    https://tools.ietf.org/html/rfc2473#section-4.1.1

14. ip-xfrm — transform configuration
    https://man7.org/linux/man-pages/man8/ip-xfrm.8.html

15. Foo over UDP
    https://lwn.net/Articles/614348

16. IPv6 Rapid Deployment
    https://tools.ietf.org/html/rfc5569

17. Generic UDP Encapsulation
    https://lwn.net/Articles/615044

18. Virtual XFRM Interfaces
    https://lwn.net/Articles/757391