Virtual Extensible LAN explained

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, Netgate, Ericsson, Mellanox,^[9] Red Hat, Joyent, and Juniper Networks.

Open source

• FreeBSD,^[10]
• OpenBSD,^[11]
• Linux,^[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. 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 that 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)

External links

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

Notes and References

1. Web site: Herrod . Steve . August 30, 2011 . Towards Virtualized Networking for the Cloud . dead . https://web.archive.org/web/20110912122246/http://blogs.vmware.com/console/2011/08/towards-virtualized-networking-for-the-cloud.html . 2011-09-12 . 2013-02-25 . VMware.
2. Web site: Configuring VXLANs. Cisco. 2024-04-17.
3. Web site: Running OpenStack over a VXLAN Fabric . 2013-11-08 . 2016-07-04 . Andre Pech . openstack.org . 8, 12.
4. Web site: Open vSwitch Manual: vtep – hardware_vtep database schema . 2016-07-04 . openvswitch.org.
5. Arista Expands Leaf Switch Product Portfolio. Arista Networks. 22 October 2014. 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. Web site: VMware, Cisco stretch virtual LANs across the heavens . Timothy Prickett Morgan . The Register . 30 August 2011 . 2013-02-25.
7. Web site: VXLAN Bridges Virtual and Physical Networks to the Cloud . 2013-12-01.
8. Web site: Huawei CE12800 Series Data Center Switches - Huawei products . December 2012 . Huawei.
9. Web site: Mellanox adds VM-flitting to ConnectX-3 adapters - Going Pro with VXLAN . April 23, 2013 . The Register . Timothy Pricket Morgan.
10. Web site: FreeBSD 10.2-RELEASE Release Notes. The FreeBSD Project. 30 June 2016.
11. Web site: OpenBSD vxlan implementation . October 14, 2013 . Reyk Floeter . Reyk Floeter . October 14, 2013 . October 29, 2014 . https://web.archive.org/web/20141029170325/http://permalink.gmane.org/gmane.os.openbsd.cvs/123361 . dead .
12. Web site: Linux Virtual eXtensible Local Area Networking documentation. Linux Kernel documentation. Sep 4, 2025.
13. Web site: What Is VXLAN . M. Mahalingam. February 22, 2013 . 2013-02-25. Huawei.