With the original VXLAN spec (RFC) there was no control plane. But Flood and Learn was used via either IR or multicast head-end replication. EVPN was then introduced as the control plane.

My question is in an environment with IP Multicast, VXLAN and EVPN configuration, in what circumstances would it use head-end replication (IP Multicast). Is this just used for BUM traffic?


2 Answers 2


VTEPs still need to know where traffic belongs. In simple terms, EVPN is "front loading" the MAC-destination tables. If a host is not already known (via EVPN, other vendor proprietary means, or previous multicast discovery), the VTEP will still attempt multicast discovery.


I know this is already answered but let me add some colors, As Ricky mentioned VTEP still need to know where are the mac/host located and to find them it need to send ARP. It use IR or Multicast as vehicle to send ARP packets to other VTEP, it's no different than classic ethernet design (This method isn't scalable). To improve it EVPN born which still use flood/learn but then it will offload your mac-table to BGP routes so now you have all your mac/vtep relationship in BGP with Centralized database so now if any VTEP need to talk to other VTEP they can ask BGP and get that information from there which reduce flood/learning process greatly.

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