Virtual Extensible LAN

Virtual eXtensible LAN (VXLAN) is a network virtualization technology that uses a VLAN-like encapsulation technique to encapsulate OSI layer 2 Ethernet frames within layer 4 UDP datagrams, using 4789 as the default IANA-assigned destination UDP port number,^[1] although many implementations that predate the IANA assignment use port 8472. VXLAN attempts to address the scalability problems associated with large cloud computing deployments. ^[2] VXLAN endpoints, which terminate VXLAN tunnels and may be either virtual or physical switch ports, are known as VXLAN tunnel endpoints (VTEPs).^[3]^[4]

History

VXLAN is an evolution of efforts to standardize on an overlay encapsulation protocol. Compared to single-tagged IEEE 802.1Q VLANs which provide a limited number of layer-2 VLANs (4094, using a 12-bit VLAN ID), VXLAN increases scalability up to about 16 million logical networks (using a 24-bit VNID) and allows for layer-2 adjacency across IP networks. Multicast or unicast with head-end replication (HER) is used to flood Broadcast, unknown-unicast and multicast traffic.^[5]

The VXLAN specification was originally created by VMware, Arista Networks and Cisco.^[6]^[7]

Implementations

VXLAN is widely, but not universally, implemented in commercial networking equipment. Several open-source implementations of VXLAN also exist.

Commercial

Arista, Cisco, and VMware were the originators of VXLAN and support it in various products.

Other backers of the VXLAN technology include Huawei,^[8] Broadcom, Citrix, Pica8, Big Switch Networks, Arrcus, Cumulus Networks, Dell EMC, Ericsson, Mellanox,^[9] Red Hat,^[10] Joyent, and Juniper Networks.

Open source

FreeBSD,^[11]
OpenBSD,^[12]
Open vSwitch is an example of a software-based virtual network switch that supports VXLAN overlay networks.

Standards specifications

VXLAN is officially documented by the IETF in RFC 7348.^[10] VXLAN encapsulates a MAC frame in a UDP datagram for transport across an IP network,^[13] creating an overlay network or tunnel.

Alternative technologies

Alternative technologies addressing the same or similar operational concerns, include:

IEEE 802.1ad ("Q-in-Q"), which greatly increases the number of VLANs supported by standard IEEE 802 Ethernet beyond 4K.
IEEE 802.1ah ("MAC-in-MAC"), which supports tunneling Ethernet in a way which greatly increases the number of VLANs supported while avoiding a large increase in the size of the MAC Address table in a Carrier Ethernet deployment.
Network Virtualization using Generic Route Encapsulation (NVGRE), which uses different framing but has similar goals to VxLAN.

References

^ Herrod, Steve (August 30, 2011). "Towards Virtualized Networking for the Cloud". VMware. Archived from the original on 2011-09-12. Retrieved 2013-02-25.
^ "Configuring VXLANs" (PDF). Cisco. Retrieved 2024-04-17.
^ Andre Pech (2013-11-08). "Running OpenStack over a VXLAN Fabric" (PDF). openstack.org. pp. 8, 12. Retrieved 2016-07-04.
^ "Open vSwitch Manual: vtep – hardware_vtep database schema". openvswitch.org. Retrieved 2016-07-04.
^ "Arista Expands Leaf Switch Product Portfolio" (Press release). Arista Networks. 22 October 2014. Retrieved 8 November 2014. Arista's updated VXLAN implementation eliminates the need for multicast in the underlay network by using Head End Replication for forwarding broadcast, multicast and unknown unicast traffic
^ Timothy Prickett Morgan (30 August 2011). "VMware, Cisco stretch virtual LANs across the heavens". The Register. Retrieved 2013-02-25.
^ "VXLAN Bridges Virtual and Physical Networks to the Cloud" (PDF). Retrieved 2013-12-01.
^ "Huawei CE12800 Series Data Center Switches - Huawei products". Huawei. December 2012.
^ Timothy Pricket Morgan (April 23, 2013). "Mellanox adds VM-flitting to ConnectX-3 adapters - Going Pro with VXLAN". The Register.
^ ^a ^b M. Mahalingam; D. Dutt; K. Duda; P. Agarwal; L. Kreeger; T. Sridhar; M. Bursell; C. Wright (August 2014). Virtual eXtensible Local Area Network (VXLAN). Internet Engineering Task Force. doi:10.17487/RFC7348. ISSN 2070-1721. RFC 7348. Informational.
^ "FreeBSD 10.2-RELEASE Release Notes". The FreeBSD Project. Retrieved 30 June 2016.
^ Reyk Floeter (October 14, 2013). "OpenBSD vxlan implementation". Reyk Floeter.
^ M. Mahalingam (February 22, 2013). "What Is VXLAN". Huawei. Retrieved 2013-02-25.