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SYSTEMD.NETDEV(5) systemd.network SYSTEMD.NETDEV(5)

systemd.netdev - Virtual Network Device configuration

netdev.netdev

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

The main Virtual Network Device file must have the extension .netdev; other extensions are ignored. Virtual network devices are created as soon as networkd is started. If a netdev with the specified name already exists, networkd will use that as-is rather than create its own. Note that the settings of the pre-existing netdev will not be changed by networkd.

The .netdev files are read from the files located in the system network directory /usr/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 /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 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 /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.)

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.Local configuration
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.
gretap A Level 2 GRE tunnel over IPv4.
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.
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.
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.
netdevsim A simulator. This simulated networking device is used for testing various networking APIs and at this time is particularly focused on testing hardware offloading related interfaces.
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.

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, then previously assigned value is cleared.

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, then previously assigned value is cleared.

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, then previously assigned value is cleared.

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, then previously assigned value is cleared.

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, then previously assigned value is cleared.

The "[NetDev]" section accepts the following keys:

Description=

A free-form description of the netdev.

Name=

The interface name used when creating the netdev. This option is compulsory.

Kind=

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

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.

MACAddress=

The MAC address to use for the device. For "tun" or "tap" devices, setting MACAddress= in the "[NetDev]" section is not supported. Please specify it in "[Link]" section of the corresponding systemd.network(5) file. If this option is not set, "vlan" devices inherit the MAC address of the physical interface. For other kind of netdevs, if this option is not set, then MAC address is generated based on the interface name and the machine-id(5).

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.

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.

ForwardDelaySec=

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

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.

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.

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).

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.

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.

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.

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.

STP=

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

MulticastIGMPVersion=

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

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 option is compulsory.

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.

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.

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.

ReorderHeader=

Takes a boolean. The VLAN reorder header is set VLAN interfaces behave like physical interfaces. When unset, the kernel's default will be used.

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", and "passthru".

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

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".

Flags=

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

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

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.

Remote=

Configures destination IP address.

Local=

Configures local IP address.

Group=

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

TOS=

The Type Of Service byte value for a vxlan interface.

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.

MacLearning=

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

FDBAgeingSec=

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

MaximumFDBEntries=

Configures maximum number of FDB entries.

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 (DVOE)[5] clients. Defaults to false.

L2MissNotification=

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

L3MissNotification=

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

RouteShortCircuit=

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

UDPChecksum=

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

UDP6ZeroChecksumTx=

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

UDP6ZeroChecksumRx=

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

RemoteChecksumTx=

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

RemoteChecksumRx=

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

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[6] document. Defaults to false.

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[7] document. If destination port is not specified and Generic Protocol Extension is set then default port of 4790 is used. Defaults to false.

DestinationPort=

Configures the default destination UDP port on a per-device basis. If destination port is not specified then Linux kernel default will be used. Set destination port 4789 to get the IANA assigned value. If not set or if the destination port is assigned the empty string the default port of 4789 is used.

PortRange=

Configures VXLAN port range. VXLAN bases source UDP port based on flow to help the receiver to be able to load balance based on outer header flow. It restricts the port range to the normal UDP local ports, and allows overriding via configuration.

FlowLabel=

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

IPDoNotFragment=

Allows to set 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.

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

Id=

Specifies the Virtual Network Identifier (VNI) to use. Ranges [0-16777215]. This field is mandatory.

Remote=

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

TOS=

Specifies the TOS value to use in outgoing packets. Ranges [1-255].

TTL=

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

UDPChecksum=

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

UDP6ZeroChecksumTx=

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

UDP6ZeroChecksumRx=

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

DestinationPort=

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

FlowLabel=

Specifies the flow label to use in outgoing packets.

IPDoNotFragment=

Accepts the same key in "[VXLAN]" section.

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

TunnelId=

Specifies the tunnel id. The value used must match the "PeerTunnelId=" value being used at the peer. Ranges a number between 1 and 4294967295). This option is compulsory.

PeerTunnelId=

Specifies the peer tunnel id. The value used must match the "PeerTunnelId=" value being used at the peer. Ranges a number between 1 and 4294967295). This option is compulsory.

Remote=

Specifies the IP address of the remote peer. This option is compulsory.

Local=

Specifies the IP address of the local interface. Takes an IP address, or the special values "auto", "static", or "dynamic". When an address is set, then the local interface must have the address. If "auto", then one of the addresses on the local interface is used. Similarly, if "static" or "dynamic" is set, then one of the static or dynamic addresses on the local interface is used. Defaults to "auto".

EncapsulationType=

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

UDPSourcePort=

Specifies the UDP source port to be used for the tunnel. When UDP encapsulation is selected it's mandotory. Ignored when ip encapsulation is selected.

DestinationPort=

Specifies destination port. When UDP encapsulation is selected it's mandotory. Ignored when ip encapsulation is selected.

UDPChecksum=

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

UDP6ZeroChecksumTx=

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

UDP6ZeroChecksumRx=

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

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

Name=

Specifies the name of the session. This option is compulsory.

SessionId=

Specifies the session id. The value used must match the "SessionId=" value being used at the peer. Ranges a number between 1 and 4294967295). This option is compulsory.

PeerSessionId=

Specifies the peer session id. The value used must match the "PeerSessionId=" value being used at the peer. Ranges a number between 1 and 4294967295). This option is compulsory.

Layer2SpecificHeader=

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

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.

Encrypt=

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

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.

MACAddress=

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

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.

KeyId=

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

Key=

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

KeyFile=

Takes a 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.

Activate=

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

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.

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

Port=

Accepts the same key in "[MACsecReceiveChannel]" section.

MACAddress=

Accepts the same key in "[MACsecReceiveChannel]" section.

PacketNumber=

Accepts the same key in "[MACsecTransmitAssociation]" section.

KeyId=

Accepts the same key in "[MACsecTransmitAssociation]" section.

Key=

Accepts the same key in "[MACsecTransmitAssociation]" section.

KeyFile=

Accepts the same key in "[MACsecTransmitAssociation]" section.

Activate=

Accepts the same key in "[MACsecTransmitAssociation]" section.

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:

Local=

A static local address for tunneled packets. It must be an address on another interface of this host, or the special value "any".

Remote=

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

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[8] document.

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: inherit. The default value for IPv6 tunnels is 64.

DiscoverPathMTU=

Takes a boolean. When true, enables Path MTU Discovery on the tunnel.

IPv6FlowLabel=

Configures the 20-bit flow label (see RFC 6437[9]) field in the IPv6 header (see RFC 2460[10]), 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.

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".

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[11]). The valid range is 0–255 and "none". Defaults to 4.

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[12] for details. It is only used for VTI/VTI6, GRE, GRETAP, and ERSPAN tunnels.

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.

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.

Mode=

An "ip6tnl" tunnel can be in one of three modes "ip6ip6" for IPv6 over IPv6, "ipip6" for IPv4 over IPv6 or "any" for either.

Independent=

Takes a boolean. When true tunnel does not require .network file. Created as "tunnel@NONE". Defaults to "false".

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".

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.

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[13]

FOUDestinationPort=

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

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.

Encapsulation=

Accepts the same key as in the "[FooOverUDP]" section.

IPv6RapidDeploymentPrefix=

Reconfigure the tunnel for IPv6 Rapid Deployment[14], also known as 6rd. The value is an ISP-specific IPv6 prefix with a non-zero length. Only applicable to SIT tunnels.

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.

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.

ERSPANIndex=

Specifies the ERSPAN index field for the interface, an integer in the range 1-1048575 associated with the ERSPAN traffic's source port and direction. This field is mandatory.

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[15]. Defaults to "FooOverUDP".

Port=

Specifies the port number, where the IP encapsulation packets will arrive. Please take note that the packets will arrive with the encapsulation will be removed. Then they will be manually fed back into the network stack, and sent ahead for delivery to the real destination. This option is mandatory.

PeerPort=

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

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.

Peer=

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

Local=

Configures local IP address.

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 option is compulsory.

MACAddress=

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

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 option is compulsory.

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".

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".

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".

User=

User to grant access to the /dev/net/tun device.

Group=

Group to grant access to the /dev/net/tun device.

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

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)). This option or PrivateKeyFile= is mandatory to use WireGuard. Note that because this information is secret, you may want to set the permissions of the .netdev file to be owned by "root:systemd-network" with a "0640" file mode.

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.

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".

FirewallMark=

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

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 is mandatory for this section.

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. Note that because this information is secret, you may want to set the permissions of the .netdev file to be owned by "root:systemd-networkd" with a "0640" file mode.

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.

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. 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.

Endpoint=

Sets an endpoint IP address or hostname, followed by a colon, and then a port number. 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.

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.

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".

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".

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".

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.

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.

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.

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.

AdSelect=

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

AdActorSystemPriority=

Specifies the 802.3ad actor system priority. Ranges [1-65535].

AdUserPortKey=

Specifies the 802.3ad user defined portion of the port key. Ranges [0-1023].

AdActorSystem=

Specifies the 802.3ad system mac address. This can not be either NULL or Multicast.

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".

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".

ARPIntervalSec=

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

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.

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".

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".

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.

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.

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.

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 times it is nice to allow duplicate frames to be delivered. The default value is false (drop duplicate frames received on inactive ports).

DynamicTransmitLoadBalancing=

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

MinLinks=

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

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

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 0-0xffffffff, defaults to 0.

Independent=

Takes a boolean. If set to "no", the xfrm interface should have an underlying device which can be used for hardware offloading. Defaults to "no". See systemd.network(5) for how to configure the underlying device.

For more detail information see Virtual xfrm interfaces[16]

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

Table=

The numeric routing table identifier. This option is compulsory.

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-vti.netdev

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

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

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

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

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

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

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

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

Create a VRF interface with table 42.

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

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

Create a MacVTap device.

[NetDev]
Name=macvtap-test
Kind=macvtap
      

Example 16. /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 17. /etc/systemd/network/27-xfrm.netdev

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

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

1.
Linux Ethernet Bonding Driver HOWTO
https://www.kernel.org/doc/Documentation/networking/bonding.txt
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://www.kernel.org/doc/Documentation/networking/vrf.txt
5.
(DVOE)
https://en.wikipedia.org/wiki/Distributed_Overlay_Virtual_Ethernet
6.
VXLAN Group Policy
https://tools.ietf.org/html/draft-smith-vxlan-group-policy
7.
Generic Protocol Extension for VXLAN
https://tools.ietf.org/html/draft-ietf-nvo3-vxlan-gpe-07
8.
Type of Service in the Internet Protocol Suite
http://tools.ietf.org/html/rfc1349
9.
RFC 6437
https://tools.ietf.org/html/rfc6437
10.
RFC 2460
https://tools.ietf.org/html/rfc2460
11.
RFC 2473
https://tools.ietf.org/html/rfc2473#section-4.1.1
12.
ip-xfrm — transform configuration
http://man7.org/linux/man-pages/man8/ip-xfrm.8.html
13.
Foo over UDP
https://lwn.net/Articles/614348
14.
IPv6 Rapid Deployment
https://tools.ietf.org/html/rfc5569
15.
Generic UDP Encapsulation
https://lwn.net/Articles/615044
16.
Virtual xfrm interfaces
https://lwn.net/Articles/757391
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