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EVPN/VXLAN: BGP Control Plane for Overlay Networks

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EVPN: BGP as the control plane for VXLAN overlays

VXLAN (Virtual Extensible LAN) creates Layer 2 overlays over Layer 3 underlay networks — essential for modern datacenter fabrics where VMs on different physical servers need to share a broadcast domain. But vanilla VXLAN uses flood-and-learn: unknown MAC destinations trigger floods to every VTEP in the fabric, causing massive BUM (Broadcast, Unknown unicast, Multicast) traffic.

EVPN (RFC 7432) solves this by using BGP as the control plane: VTEPs advertise their MAC/IP bindings via BGP route types, so every VTEP knows exactly where every VM lives before the first packet arrives. No flooding needed.

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