NAME¶
systemd.netdev - Virtual Network Device configuration
DESCRIPTION¶
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 /lib/systemd/network, the volatile runtime network
directory /run/systemd/network and the local administration network
directory /etc/systemd/network. All configuration files are collectively
sorted and processed in lexical order, regardless of the directories in
which they live. However, files with identical filenames replace each other.
Files in /etc have the highest priority, files in /run take precedence over
files with the same name in /lib. This can be used to override a
system-supplied configuration file with a local file if needed. As a special
case, an empty file (file size 0) or symlink with the same name pointing to
/dev/null disables the configuration file entirely (it is
"masked").
Along with the 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 /lib/systemd/network or /run/systemd/network
directories. Drop-in files in /etc take precedence over those in /run which
in turn take precedence over those in /lib. Drop-in files under any of these
directories take precedence over the main netdev file wherever located. (Of
course, since /run is temporary and /usr/lib is for vendors, it is unlikely
drop-ins should be used in either of those places.)
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.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. |
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. |
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. |
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. |
[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.
Virtualization=
Checks whether the system is executed in a virtualized
environment and optionally test whether it is a specific implementation. See
"ConditionVirtualization=" in
systemd.unit(5) for
details.
KernelCommandLine=
Checks whether a specific kernel command line option is
set (or if prefixed with the exclamation mark unset). See
"ConditionKernelCommandLine=" in
systemd.unit(5) for
details.
Architecture=
Checks whether the system is running on a specific
architecture. See "ConditionArchitecture=" in
systemd.unit(5)
for details.
[NETDEV] SECTION OPTIONS¶
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. This key is not currently supported for "tun" or
"tap" devices.
MACAddress=
The MAC address to use for the device. If none is given,
one is generated based on the interface name and the
machine-id(5).
This key is not currently supported for "tun" or "tap"
devices.
[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.
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.
DefaultPVID=
This specifies the default port VLAN ID of a newly
attached bridge port.
MulticastQuerier=
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 setting applies.
MulticastSnooping=
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 setting applies.
VLANFiltering=
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 setting
applies.
STP=
A boolean. This enables the bridge's Spanning Tree
Protocol (STP). When unset, the kernel's default setting applies.
[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 option is compulsory.
[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", and
"passthru".
[MACVTAP] SECTION OPTIONS¶
The "[MACVTAP]" section applies for netdevs of kind
"macvtap" and accepts the same key 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" and "L3".
[VXLAN] SECTION OPTIONS¶
The "[VXLAN]" section only applies for netdevs of kind
"vxlan", and accepts the following keys:
Id=
The VXLAN ID to use.
Group=
An assigned multicast group IP 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. N is a number in the range 1–255. 0 is a special value
meaning that packets inherit the TTL value.
MacLearning=
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.
ARPProxy=
A boolean. When true, enables ARP proxying.
L2MissNotification=
A boolean. When true, enables netlink LLADDR miss
notifications.
L3MissNotification=
A boolean. When true, enables netlink IP address miss
notifications.
RouteShortCircuit=
A boolean. When true, route short circuiting is turned
on.
UDPChecksum=
A boolean. When true, transmitting UDP checksums when
doing VXLAN/IPv4 is turned on.
UDP6ZeroChecksumTx=
A boolean. When true, sending zero checksums in
VXLAN/IPv6 is turned on.
UDP6ZeroChecksumRx=
A boolean. When true, receiving zero checksums in
VXLAN/IPv6 is turned on.
RemoteChecksumTx=
A boolean. When true, remote transmit checksum offload of
VXLAN is turned on.
RemoteChecksumRx=
A boolean. When true, remote receive checksum offload in
VXLAN is turned on.
GroupPolicyExtension=
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[5]
document. 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, and destination port 0 to get default values.
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.
[TUNNEL] SECTION OPTIONS¶
The "[Tunnel]" section only applies for netdevs of kind
"ipip", "sit", "gre", "gretap",
"ip6gre", "ip6gretap", "vti", "vti6",
and "ip6tnl" and accepts the following keys:
Local=
A static local address for tunneled packets. It must be
an address on another interface of this host.
Remote=
The remote endpoint of the tunnel.
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[6] 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=
A boolean. When true, enables Path MTU Discovery on the
tunnel.
IPv6FlowLabel=
Configures the 20-bit flow label (see RFC 6437[7])
field in the IPv6 header (see RFC 2460[8]), 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=
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[9]). 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[10] for details. It is only
used for VTI/VTI6 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
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
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.
[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
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.
[TUN] SECTION OPTIONS¶
The "[Tun]" section only applies for netdevs of kind "tun",
and accepts the following keys:
OneQueue=
Takes a boolean argument. Configures whether all packets
are queued at the device (enabled), or a fixed number of packets are queued at
the device and the rest at the "qdisc". Defaults to
"no".
MultiQueue=
Takes a boolean argument. Configures whether to use
multiple file descriptors (queues) to parallelize packets sending and
receiving. Defaults to "no".
PacketInfo=
Takes a boolean argument. 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 argument. Configures IFF_VNET_HDR flag
for a 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.
[TAP] SECTION OPTIONS¶
The "[Tap]" section only applies for netdevs of kind "tap",
and accepts the same keys as the "[Tun]" section.
[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".
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".
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 in
milliseconds. A value of 0 disables ARP monitoring. The default value is
0.
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=
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).
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]
EXAMPLE¶
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/25-tap.netdev
[NetDev]
Name=tap-test
Kind=tap
[Tap]
MultiQueue=true
PacketInfo=true
Example 5. /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 6. /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 7. /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 8. /etc/systemd/network/25-veth.netdev
[NetDev]
Name=veth-test
Kind=veth
[Peer]
Name=veth-peer
Example 9. /etc/systemd/network/25-bond.netdev
[NetDev]
Name=bond1
Kind=bond
[Bond]
Mode=802.3ad
TransmitHashPolicy=layer3+4
MIIMonitorSec=1s
LACPTransmitRate=fast
Example 10. /etc/systemd/network/25-dummy.netdev
[NetDev]
Name=dummy-test
Kind=dummy
MACAddress=12:34:56:78:9a:bc
Example 11. /etc/systemd/network/25-vrf.netdev
Create a VRF interface with table 42.
[NetDev]
Name=vrf-test
Kind=vrf
[VRF]
TableId=42
NOTES¶
- 1.
- Linux Ethernet Bonding Driver HOWTO
- 2.
- RFC 2784
- 3.
- IEEE 802.1Q
- 4.
- VRF
- 5.
- VXLAN Group Policy
- 6.
- Type of Service in the Internet Protocol Suite
- 7.
- RFC 6437
- 8.
- RFC 2460
- 9.
- RFC 2473
- 10.
- ip-xfrm — transform configuration