Beyond Flood and Learn

In a traditional network, a switch learns where a computer is by looking at the source MAC address of incoming frames. If the target is unknown, it broadcasts (floods) the packet. In a massive data center fabric with 100,000 servers, this flooding would bring the network to its knees.

EVPN Route Types (The Essentials)

BGP EVPN uses specific "Route Types" to describe different network states:

• Type-2 (MAC/IP Advertisement): This is the most common. It tells the network: "MAC A with IP B is located behind VTEP C."
• Type-3 (Inclusive Multicast): Used to handle broadcast/multicast traffic by building a logical distribution tree between VTEPs.
• Type-5 (IP Prefix): Used for routing external traffic into the fabric (e.g., reaching the Internet).

ARP Suppression

One of the biggest advantages of EVPN is ARP Suppression. When a computer asks "Who has IP X?", the local switch intercepts the request. Since it already knows the answer from its BGP EVPN table, it answers locally. The ARP request never needs to be flooded across the network.

Multi-Homing with ESI

Traditional networks use Link Aggregation (LACP) to connect a server to two switches. EVPN introduces the Ethernet Segment Identifier (ESI), which allows two independent switches to act as a single logical VTEP to a server, without needing a proprietary "stacking" or "VPC" cable between them.

Conclusion

BGP EVPN is currently the gold standard for data center and campus network design. By leveraging the stability and scalability of the BGP protocol—the same protocol that runs the global internet—EVPN brings carrier-grade reliability to the local network.