vxlan
—
Virtual eXtensible LAN interface
To compile this driver into the kernel, place the following line in your kernel
configuration file:
device vxlan
Alternatively, to load the driver as a module at boot time, place the following
line in
loader.conf(5):
The
vxlan
driver creates a virtual tunnel
endpoint in a
vxlan
segment. A
vxlan
segment is a virtual Layer 2
(Ethernet) network that is overlaid in a Layer 3 (IP/UDP) network.
vxlan
is analogous to
vlan(4)
but is designed to be better suited for large, multiple tenant data center
environments.
Each
vxlan
interface is created at runtime
using interface cloning. This is most easily done with the
ifconfig(8)
create
command or using the
cloned_interfaces variable in
rc.conf(5).
The interface may be removed with the
ifconfig(8)
destroy
command.
The
vxlan
driver creates a pseudo Ethernet
network interface that supports the usual network
ioctl(2)s
and is thus can be used with
ifconfig(8)
like any other Ethernet interface. The
vxlan
interface encapsulates the Ethernet
frame by prepending IP/UDP and
vxlan
headers. Thus, the encapsulated (inner) frame is able to transmitted over a
routed, Layer 3 network to the remote host.
The
vxlan
interface may be configured in
either unicast or multicast mode. When in unicast mode, the interface creates
a tunnel to a single remote host, and all traffic is transmitted to that host.
When in multicast mode, the interface joins an IP multicast group, and
receives packets sent to the group address, and transmits packets to either
the multicast group address, or directly the remote host if there is an
appropriate forwarding table entry.
When the
vxlan
interface is brought up, a
UDP(4)
socket(9)
is created based on the configuration, such as the local address for unicast
mode or the group address for multicast mode, and the listening (local) port
number. Since multiple
vxlan
interfaces may
be created that either use the same local address or join the same group
address, and use the same port, the driver may share a socket among multiple
interfaces. However, each interface within a socket must belong to a unique
vxlan
segment. The analogous
vlan(4)
configuration would be a physical interface configured as the parent device
for multiple VLAN interfaces, each with a unique VLAN tag. Each
vxlan
segment is identified by a 24-bit
value in the
vxlan
header called the
“VXLAN Network Identifier”, or VNI.
When configured with the
ifconfig(8)
vxlanlearn
parameter, the interface
dynamically creates forwarding table entries from received packets. An entry
in the forwarding table maps the inner source MAC address to the outer remote
IP address. During transmit, the interface attempts to lookup an entry for the
encapsulated destination MAC address. If an entry is found, the IP address in
the entry is used to directly transmit the encapsulated frame to the
destination. Otherwise, when configured in multicast mode, the interface must
flood the frame to all hosts in the group. The maximum number of entries in
the table is configurable with the
ifconfig(8)
vxlanmaxaddr
command. Stale entries in the
table periodically pruned. The timeout is configurable with the
ifconfig(8)
vxlantimeout
command. The table may be
viewed with the
sysctl(8)
net.link.vxlan.N.ftable.dump
command.
Since the
vxlan
interface encapsulates the
Ethernet frame with an IP, UDP, and
vxlan
header, the resulting frame may be larger than the MTU of the physical
network. The
vxlan
specification recommends
the physical network MTU be configured to use jumbo frames to accommodate the
encapsulated frame size. Alternatively, the
ifconfig(8)
mtu
command may be used to reduce the MTU
size on the
vxlan
interface to allow the
encapsulated frame to fit in the current MTU of the physical network.
Create a
vxlan
interface in unicast mode with
the
vxlanlocal
tunnel address of
192.168.100.1, and the
vxlanremote
tunnel
address of 192.168.100.2.
ifconfig vxlan create vxlanid 108 vxlanlocal 192.168.100.1 vxlanremote 192.168.100.2
Create a
vxlan
interface in multicast mode,
with the
local
address of 192.168.10.95,
and the
group
address of 224.0.2.6. The em0
interface will be used to transmit multicast packets.
ifconfig vxlan create vxlanid 42 vxlanlocal 192.168.10.95 vxlangroup 224.0.2.6 vxlandev em0
Once created, the
vxlan
interface can be
configured with
ifconfig(8).
The following when placed in the file
/etc/rc.conf will cause a vxlan interface
called “
vxlan0
” to be created, and will
configure the interface in unicast mode.
cloned_interfaces="vxlan0"
create_args_vxlan0="vxlanid 108 vxlanlocal 192.168.100.1 vxlanremote 192.168.100.2"
inet(4),
inet6(4),
vlan(4),
rc.conf(5),
ifconfig(8),
sysctl(8)
M. Mahalingam and
et al, Virtual eXtensible Local
Area Network (VXLAN): A Framework for Overlaying Virtualized Layer 2 Networks
over Layer 3 Networks, August 2014,
RFC 7348.
The
vxlan
driver was written by
Bryan Venteicher
⟨bryanv@freebsd.org⟩.