Free Nokia 4A0-D03 Practice Exam with Questions & Answers | Set: 2

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

VXLAN provides a Layer 2 overlay over a Layer 3 underlay by encapsulating Ethernet frames in UDP/IP. This allows tenant bridge domains to span a routed IP fabric without requiring the underlay itself to behave like one large Layer 2 network. VXLAN uses a 24-bit VXLAN Network Identifier, which supports approximately 16 million logical overlays, far exceeding the scale of traditional 12-bit VLAN IDs. Because the VXLAN underlay is IP-routed, traffic can benefit from ECMP across equal-cost paths, improving fabric utilization and resiliency. The false statement is B. VXLAN was not originally developed specifically to support EVPN. VXLAN began as a data-plane overlay encapsulation technology, while EVPN later became the preferred control plane for distributing MAC, MAC/IP, multicast, and prefix reachability in VXLAN-based fabrics. In modern data center design, EVPN and VXLAN are commonly paired: VXLAN supplies the encapsulation and VNI-based segmentation, while EVPN supplies scalable control-plane learning and signaling. Reference: VXLAN data plane, EVPN control plane, ECMP underlay, VNI-based tenant isolation.

================

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.

================

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.

================

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

This setup represents single-active Layer 2 EVPN multi-homing. In single-active mode, the Ethernet Segment is configured so that only one PE acts as the active forwarding node for a given service, while the other remains standby. The ports connecting to the host are associated with ES-1 so the EVPN control plane can perform Ethernet Segment discovery, DF election, and standby behavior. If Leaf1 is the active/DF node for the service, all traffic to and from the host flows through Leaf1 until a failure or DF transition occurs. Option D is false because a host LAG is not required for this single-active topology. A LAG is typically required for all-active L2 multi-homing, where the host must treat multiple physical links toward different leaf routers as one logical bundle. In single-active operation, the host can be connected through separate physical links or active/standby access behavior without requiring LACP bundling. The EVPN PEs enforce the active path selection through DF and ES state rather than relying on host-side LAG hashing. Reference: single-active EVPN multi-homing, Ethernet Segment port association, DF-controlled active forwarding.

================

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

Asymmetric routing relies heavily on host MAC/IP information because the ingress PE performs routing into the destination subnet and then sends the frame across the overlay using the destination MAC-VRF/VNI. This means PEs require enough ARP and MAC/IP binding information to forward traffic toward remote hosts correctly. If a host has multiple IP addresses on the same interface, separate EVPN route type 2 advertisements may be needed to communicate each IP-to-MAC binding. The ingress and egress PEs participate in MAC and IP forwarding across the end-to-end service path, but the forwarding responsibilities differ by direction and stage. The false statement is option C. The statement says all MAC-VRFs connected to the L3 EVPN network must exist on each PE, but that is not the correct requirement in this question's verified answer set. In practical EVPN designs, the exact MAC-VRF placement depends on whether the service is implemented as asymmetric, symmetric, interface-less, or interface-ful routing. Here, the course answer marks the universal MAC-VRF requirement as false. Reference: asymmetric L3 EVPN routing, RT-2 MAC/IP advertisements, ARP and MAC forwarding behavior.

================

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

EVPN route type 2 carries MAC/IP advertisement information. It is central to host-based routing and to designs where the fabric must distribute host MAC-to-IP bindings for integrated routing and bridging. In host routing, RT-2 is required because individual host reachability is signaled through MAC/IP advertisements. In interface-less prefix routing, RT-2 is still needed because the system relies on host or gateway MAC/IP information associated with the IRB and distributed gateway behavior. Interface-ful unnumbered designs may also require RT-2-style information to resolve next-hop or adjacency behavior because the routed interface does not use a conventional numbered next-hop model. Prefix routing with interface-ful numbered operation is different. In that model, the routed interface has explicit IP addressing and prefix reachability can be carried with L3 prefix routes without requiring EVPN RT-2 host MAC/IP advertisement as a dependency. Therefore, the symmetric routing option that does not require EVPN route type 2 is prefix routing interface-ful numbered. Reference: symmetric L3 EVPN routing models, RT-2 MAC/IP advertisements, prefix routing behavior.

================