Comprehensive and Detailed 150 to 250 words of Explanation From [SR Linux EVPN and Data Center Interconnect/Course Guide/topics]:
In asymmetric L3 EVPN routing, the ingress PE performs the routing decision and then sends traffic across the overlay in the context of the destination MAC-VRF. The egress PE performs Layer 2 MAC forwarding only toward the destination host. This is why options A and B correctly describe asymmetric data-plane behavior. Asymmetric routing relies heavily on EVPN route type 2 MAC/IP Advertisement routes because the ingress PE must know the destination host's MAC/IP binding and the destination bridge domain information. EVPN route type 5, which advertises IP prefixes, is a symmetric L3 EVPN mechanism and is not mandatory for asymmetric routing. Therefore, option C is false. Option D is treated as correct in this asymmetric-routing model because each PE participating in inter-subnet forwarding needs the destination MAC-VRF context to encapsulate traffic toward the correct L2 VNI. This requirement is one reason asymmetric routing scales less efficiently than symmetric routing: MAC-VRF presence and host reachability information must be broadly available. Symmetric routing improves scale by using an IP-VRF routed VXLAN interface and RT-5 prefix routes instead. Reference: asymmetric L3 EVPN routing, ingress IP/MAC forwarding, egress MAC forwarding, RT-2 versus RT-5 usage.
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