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.

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)