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, 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.