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

A decoupled gateway-based DCI model separates the data center border-leaf function from the WAN PE function. This separation is the key design point. The border leaf remains part of the data center EVPN/VXLAN environment, while the WAN PE participates in WAN VPN transport and policy enforcement. Because the roles are split across two devices, the handoff between the border leaf and WAN PE provides a clean administrative and operational boundary. That boundary is useful for security policy, QoS marking, traffic classification, and troubleshooting ownership. The WAN does not need direct reachability to every leaf and route reflector as in a gateway-less model. The WAN PE also does not peer directly with the data center route reflector in a decoupled model; route exchange occurs through the border-leaf/WAN-PE handoff. VXLAN tunnels between leaf routers across different data centers are characteristic of gateway-less extension, not decoupled gateway operation. Therefore, the statement about clear demarcation between the data center border leaf and WAN PE is the accurate description. Reference: decoupled gateway-based DCI, security/QoS demarcation, WAN PE separation.

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

An anycast-gateway IRB allows multiple PEs to present the same default-gateway IP address to hosts in the same subnet. This is the mechanism that enables distributed gateway behavior in EVPN fabrics. The same anycast gateway IP may be configured on equivalent IRB subinterfaces across remote PEs participating in the same IP-VRF, allowing hosts to use the nearest leaf as their default gateway without changing their gateway address. SR Linux also associates gateway MAC information with the IRB, including virtual gateway MAC behavior used inside the MAC-VRF forwarding table. Option C is false because the anycast gateway IP is not treated as a normal unique host route that appears in the IP-VRF route table alongside the subnet prefix. The subnet route is installed for the connected network, but the shared anycast gateway address is a gateway function, not a separately advertised host endpoint that should appear as ordinary routed host reachability. Treating the anycast IP as a regular host route would undermine the distributed gateway model and create ambiguous ownership across PEs. Reference: IRB anycast gateway, MAC-VRF/IP-VRF interconnection, distributed default-gateway operation.

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

In a single-active EVPN multi-homing design, the connected PE routers perform Designated Forwarder election to determine which PE is active for the relevant service or Ethernet Segment. The DF is responsible for forwarding toward the attached segment and, in a Layer 3 multi-homing case, only the active/DF PE advertises the customer IP prefix route toward the EVPN control plane. Single-active redundancy is communicated using Ethernet Segment-related EVPN procedures, including Ethernet A-D information, so remote PEs can identify the redundancy behavior and avoid forwarding traffic to an inactive attachment. The false statement is that the elected DF uses an AD per EVI update to identify itself as primary. AD per EVI is primarily used to advertise per-service Ethernet Segment reachability and support aliasing/load-balancing behavior in multi-homed services. DF election itself is driven by Ethernet Segment route procedures, not by the DF declaring itself primary through AD per EVI. Therefore, option B misstates the role of AD per EVI in the single-active L3 multi-homing control plane. Reference: EVPN DF election, single-active multi-homing, Ethernet A-D routes.

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

An IRB interface is the logical connection point between a Layer 2 MAC-VRF and a Layer 3 IP-VRF. It provides the routed gateway function for hosts in the bridge domain while allowing traffic to move into the routed VRF for inter-subnet forwarding. The correct statement is that when an IRB sub-interface has multiple IP addresses, one can be designated as the primary. This is important because the primary address is used for normal gateway or subnet behavior when more than one address is present on the same routed interface context. Option A is inaccurate because the question is about an IRB sub-interface, not a generic subinterface selection between bridge or routed access modes. Option B is not the defining multi-homing model; EVPN multi-homing is implemented through Ethernet Segment association and MAC-VRF attachment behavior, not by adding multiple IRB subinterfaces for multi-homing. Option D is also wrong because the IRB is the shared logical link between the MAC-VRF and IP-VRF; the design does not require separate IRB subinterfaces on each side as independent constructs. Reference: SR Linux IRB configuration, MAC-VRF to IP-VRF interconnection, primary IP addressing.

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

Ethernet Auto-Discovery per EVI routes are EVPN route type 1 advertisements used in multi-homing at the service-instance level. A PE sends an AD per EVI route for each MAC-VRF associated with the Ethernet Segment. These routes allow remote PEs to understand that the advertising PE has reachability to a given EVI through the shared ES. They are also used for aliasing and fast convergence, because a remote PE can treat multiple attached PEs as valid paths for traffic toward the same multihomed segment. In VXLAN EVPN, the update can include data-plane information such as the VNI, and it carries route-target information so the route is imported into the correct MAC-VRF. Option B is false because the multi-homing type or redundancy mode is not carried in the AD per EVI update as stated. Redundancy behavior is associated with Ethernet Segment-level signaling and configuration, especially ES discovery and related route attributes, not with AD per EVI as the mechanism that declares the multi-homing type. Reference: EVPN RT-1 AD per EVI, MAC-VRF association, route target, VNI, aliasing.

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