What is the difference between flood-and-learn VXLAN and VXLAN with a BGP EVPN control plane?
Show the answer
Say this first
Flood and learn has no control plane. BUM traffic goes to every VTEP in the VNI through underlay multicast or a static peer list, and VTEPs learn remote MACs from the inner source MAC of what they decapsulate, like a classic switch. EVPN uses MP-BGP to advertise MACs, IPs, prefixes and VNI membership, so VTEPs know where hosts are before traffic flows. That gives ARP suppression, integrated routing with anycast gateways, multi-tenancy through route targets, multihoming and MAC mobility handling.
Go deeper
| Flood and learn | BGP EVPN | |
|---|---|---|
| Remote MAC learning | Data plane | Control plane (type 2) |
| VTEP discovery | Multicast or static list | Type 3 routes |
| BUM | Multicast group per VNI, or static ingress replication | Ingress replication or multicast |
| ARP handling | Flooded | Suppressed when the binding is known |
| Inter-subnet routing | Separate, often a central gateway | Distributed anycast gateway, L3VNI |
| Multi-tenancy | VNI only | VRFs, RDs and route targets |
| Standards | RFC 7348 | RFC 7432 and RFC 8365 |
Points worth saying out loud
- EVPN is the control plane, VXLAN is the data plane. EVPN also runs over MPLS.
- EVPN still learns local MACs from the data plane on access ports, then advertises them.
- EVPN is MP-BGP with AFI 25 (L2VPN) and SAFI 70 (EVPN).
- Flood and learn trusts any VTEP that sends traffic. EVPN only installs what BGP advertised.
They will ask next
Does EVPN remove all flooding?
No. Broadcasts such as DHCP, ARP for unknown targets and unknown unicast are still flooded. Some platforms can suppress unknown unicast when every host is learned through the control plane.
Traps
- Saying EVPN replaces VXLAN.
How did you do?Book 3.2 Switched Ethernet