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]
• Linux, ^[13]
• 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, ^[14] 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.

See also

• Distributed Overlay Virtual Ethernet (DOVE)
• Ethernet VPN (EVPN)
• GENEVE, an industry effort to unify both VXLAN and NVGRE technologies
• Generic routing encapsulation (GRE)
• IEEE 802.1ad, an Ethernet networking standard, also known as provider bridging, Stacked VLANs, or simply Q-in-Q.
• IEEE 802.1ah, an IEEE Ethernet networking standard, also known as Provider Backbone Bridging (PBB) or MAC-in-MAC.
• NVGRE, Network Virtualization using GRE, which is a similar competing specification to VxLAN.
• Overlay Transport Virtualization (OTV)
• Virtual LAN (VLAN)
• Layer 2 Tunneling Protocol (L2TP)

References

1. Herrod, Steve (August 30, 2011). "Towards Virtualized Networking for the Cloud". VMware. Archived from the original on 2011-09-12. Retrieved 2013-02-25.
2. "Configuring VXLANs" (PDF). Cisco. Retrieved 2024-04-17.
3. Andre Pech (2013-11-08). "Running OpenStack over a VXLAN Fabric" (PDF). openstack.org. pp. 8, 12. Retrieved 2016-07-04.
4. "Open vSwitch Manual: vtep – hardware_vtep database schema". openvswitch.org. Retrieved 2016-07-04.
5. "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
6. Timothy Prickett Morgan (30 August 2011). "VMware, Cisco stretch virtual LANs across the heavens". The Register. Retrieved 2013-02-25.
7. "VXLAN Bridges Virtual and Physical Networks to the Cloud" (PDF). Retrieved 2013-12-01.
8. "Huawei CE12800 Series Data Center Switches - Huawei products". Huawei. December 2012.
9. Timothy Pricket Morgan (April 23, 2013). "Mellanox adds VM-flitting to ConnectX-3 adapters - Going Pro with VXLAN". The Register.
10. 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.
11. "FreeBSD 10.2-RELEASE Release Notes". The FreeBSD Project. Retrieved 30 June 2016.
12. Reyk Floeter (October 14, 2013). "OpenBSD vxlan implementation". Reyk Floeter. Archived from the original on October 29, 2014. Retrieved October 14, 2013.
13. "Linux Virtual eXtensible Local Area Networking documentation". Linux Kernel documentation. Retrieved Sep 4, 2025.
14. M. Mahalingam (February 22, 2013). "What Is VXLAN". Huawei. Retrieved 2013-02-25.

External links

• VXLAN Deep Dive: Part 1 and Part 2, November 2012, by Joe Onisick