VXLAN - Intro

Published Oct. 11, 2023, 3:22 p.m. by alex

This will be the first post on a series documenting the ins and outs of vxlan. GNS3 will be used to to run the Arista vEOS images for labbing, and a copy of the file can be found here: (Adding at later date)

VXLAN Overview and Terms

Simply put VXLAN is just a method of extending a layer 2 broadcast domain (overlay) ontop of a layer 3 routed network (underlay).
The transition from overlay to underlay, then back again occurs on systems known as VTEPS - Virtual Tunnel Endpoint, which can either be the hosts themselves or a network switch/router.
The VTEPs are configured with a VTI - VXLAN Tunnel Interface, which has an IP address (commonly using a loopback IP). This loopback IP is the source/destination IP for the VXLAN traffic as it traverses the underlay to reach the far end VTEP, where it is then treated as a normal L2 ethernet frame to reach the destination.
Similar to Extreme network's SPB protocol, VXLAN needs an identifier for each overlay service. In this case it is called the VNI - Virtual Network ID. This ID is a binding between the Locally significant Vlan ID and the globally significant VXLAN ID. In simple terms that means you can extend different VLAN's on VTEP's as long as the VNI matches.