Comprehensive and Detailed 150 to 250 words of Explanation From [SR Linux EVPN and Data Center Interconnect/Course Guide/topics]:

In a gateway-less DCI design, there is no dedicated gateway device performing EVPN-to-WAN service interworking. Instead, the data center EVPN overlay is extended across the WAN more directly. Because leaf routers must establish overlay reachability across sites, the IP addresses of the leaf VTEPs need to be reachable through the WAN, commonly by redistributing or otherwise carrying the necessary loopback reachability. The WAN transparently carries the EVPN/VXLAN overlay, and leaf routers can establish VXLAN tunnels across the WAN to remote leaves. Option D is false because it introduces “data center gateway routers” maintaining MP-BGP EVPN peering with the data center route reflector. That is not the gateway-less model; it describes a gateway-based role that does not exist as a separate function in this architecture. In gateway-less DCI, the EVPN control-plane and VXLAN data-plane extension are handled by the fabric endpoints themselves, so the design trades demarcation and interworking control for a more direct overlay extension model. Reference: gateway-less DCI, WAN reachability for leaf VTEPs, transparent EVPN overlay carriage, VXLAN tunnel extension.

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