Virtual eXtensible LAN (VXLAN) is anetwork virtualization technology that uses aVLAN-like encapsulation technique to encapsulateOSIlayer 2Ethernet frames withinlayer 4UDP datagrams, using 4789 as the defaultIANA-assigned destination UDP port number,[1] although many implementations that predate the IANA assignment use port 8472. VXLAN attempts to address thescalability problems associated with largecloud computing deployments.[2] VXLAN endpoints, which terminate VXLAN tunnels and may be either virtual or physicalswitch ports, are known asVXLAN 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 orunicast with head-end replication (HER) is used to floodBroadcast, unknown-unicast and multicast traffic.[5]
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.
^"Arista Expands Leaf Switch Product Portfolio" (Press release). Arista Networks. 22 October 2014. Retrieved8 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
