Virtual Extensible LAN

Virtual Extensible LAN (VXLAN) is a network virtualization technology that attempts to address the scalability problems associated with large cloud computing deployments. It 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.^[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]

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] Other backers of the VXLAN technology include Huawei,^[8] Broadcom, Citrix, Pica8, Big Switch Networks, Arrcus, Cumulus Networks, Dell EMC, Ericsson, Mellanox,^[9] FreeBSD,^[10] OpenBSD,^[11] Red Hat,^[12] Joyent, and Juniper Networks.

VXLAN is officially documented by the IETF in RFC 7348.^[12] VXLAN encapsulates a MAC frame in a UDP datagram for transport across an IP network,^[13] creating an overlay network or tunnel.

Open vSwitch is an example of a software-based virtual network switch that supports VXLAN overlay networks.