VXLAN: L2 over L3, with EVPN as the control plane
Every mechanism has a step-by-step animation, the configuration explained line by line and the exam notes. Where a parameter changes the outcome, you get a simulator in which you change it yourself.
TL;DR
VXLAN puts a whole Ethernet frame into a UDP/IP packet (port 4789, an 8-byte header with a 24-bit VNI) and sends it between two VTEPs over a routed network: the same L2 domain, in different racks or data centers, with no STP and all links active. The underlay is a simple IP fabric (OSPF or eBGP, loopbacks, ECMP, an MTU 50 bytes larger). BUM traffic goes through multicast or through unicast copies (ingress replication). With BGP EVPN, the VTEPs advertise their MACs, IPs and VNIs through routes (Type 2, 3, 5) instead of learning them by flooding: ARP suppression, deterministic mobility, a distributed anycast gateway and symmetric routing through the L3VNI. Multihoming is done with vPC (anycast VTEP) or with ESI (Type 1 / 4, DF), leaving the fabric with Type 5 on a border leaf, and the link between data centers with border gateways. Most incidents come from the MTU, missing RTs and PIM that doesn't work.
How to read the notes: red = critical for the exam, green = theory, blue = numbers, yellow = pitfalls, cyan = differences between platforms and standards. In the animations, the configuration lines used in the current step are highlighted automatically; the ← → arrows change the step when the animation is selected.
The analogy, in short
Think of a campus with several buildings, where the tenant companies have offices scattered everywhere and send their mail in envelopes placed inside other envelopes: the company's internal letter (the frame) goes into an outer envelope addressed to the recipient's building (the VTEP), with the company's code on it (the VNI). The campus mail carries envelopes between buildings and doesn't read the contents; a central register (EVPN) says in advance which building everyone works in.
The model holds up to §10. From §11 on (the header variants, QoS, security, convergence), it breaks; see the full analogy and its limits in §15.