Nokia Nokia SR Linux EVPN and Data Center Interconnect 4A0-D03 Exam Dumps: Updated Questions & Answers (September 2026)

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.

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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]:

In a decoupled gateway-based DCI design, the data center border leaf and the WAN PE are separate devices. Traffic between them can be identified using VLAN tags, allowing different data center EVPN services to be mapped to corresponding WAN VPN services. This architecture provides a clean operational boundary: the border leaf remains aligned with the data center EVPN/VXLAN fabric, while the WAN PE handles WAN VPN transport, QoS, security policy, and service interconnection. The separation gives a strong demarcation point for troubleshooting and administrative control. Option D is false because the WAN PE does not maintain an MP-BGP EVPN peering session with the data center route reflector. In the decoupled model, the route reflector remains part of the data center EVPN control plane, while the WAN PE exchanges routing or service information with the border leaf through the local handoff model. Direct WAN PE-to-data-center-RR peering would blur the separation that defines the decoupled design and would make the WAN PE part of the data center EVPN overlay control plane, which is not the intended architecture. Reference: decoupled gateway DCI, VLAN handoff, WAN VPN mapping, security/QoS demarcation, route-reflector 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]:

A BGP route target is an extended community used to control which EVPN routes are imported into which MAC-VRF or IP-VRF. It is carried with EVPN updates and acts as the import/export policy tag for tenant service membership. The statement that it is a BGP extended community is correct. It is also correct that route targets support multi-tenant operation, because they allow different EVPN instances to carry potentially overlapping MAC or IP information while importing only the routes intended for that service. However, option D is false in the wording used here. The route target does not itself identify the EVPN instance in the control plane as a unique route identifier. That role is more closely associated with the route distinguisher and EVPN NLRI construction, while the route target determines import eligibility. A route target tells a receiving PE whether the route belongs in a local service instance, but it is not the unique identity of the EVPN route. This distinction is critical: route distinguishers make routes unique; route targets control route distribution and service membership. Reference: EVPN route targets, BGP extended communities, route import/export policy, RD versus RT function.

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

Proxy ARP in a Layer 2 EVPN service allows the leaf to answer ARP requests locally using learned IP/MAC bindings, reducing broadcast flooding across the overlay. SR Linux can also monitor IP duplication and MAC/IP inconsistencies in the proxy ARP table. A pending state indicates that the system has detected suspicious or conflicting information and is monitoring the binding before declaring it duplicate. If the entry becomes duplicate, SR Linux can use a blackhole behavior to prevent forwarding traffic toward a conflicted endpoint, and a special discard MAC such as 00:00:00:00:DE:AD can be associated with the duplicate entry. Option D is false because it incorrectly states that all traffic destined to 192.168.100.1 will be discarded for exactly 9 minutes. The exhibit references monitoring and hold-down behavior, but the answer key rejects the fixed “9 minutes” traffic-discard statement. The key concept is that duplicate handling protects the EVPN service from unstable or conflicting IP/MAC bindings, but the specific discard duration in option D is not correct. Reference: proxy ARP, IP duplication monitoring, duplicate-state blackhole behavior.

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

Aliasing is an EVPN multi-homing mechanism that allows remote PEs to send traffic to any eligible PE attached to the same Ethernet Segment, even if a specific MAC address was learned and advertised by only one of those PEs. This avoids a traffic bottleneck and enables load-sharing in all-active multi-homing designs. The route type used to implement this behavior is the Ethernet Auto-Discovery per EVI route, commonly referred to as AD per EVI. This route tells remote PEs that a given PE has reachability to a specific Ethernet Segment for a specific EVPN instance. When remote PEs receive these advertisements from multiple PEs for the same ESI and EVI, they can treat those PEs as valid next-hops for traffic toward that Ethernet Segment. Ethernet Segment routes support ES discovery and DF election, while IP/MAC routes advertise host MAC and optionally IP binding information. AD per ES routes are used for broader Ethernet Segment-level procedures, but aliasing at the service level relies on AD per EVI reachability. Reference: EVPN route type 1, AD per EVI, aliasing in all-active multi-homing.

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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 EVPN IRB, the ingress PE performs routing from the source subnet into the destination subnet, then forwards the packet across the VXLAN overlay using the destination MAC-VRF/VNI. The egress PE does not perform another IP-VRF lookup for that packet; it performs Layer 2 forwarding in the destination MAC-VRF. In this scenario, Host-2 sends traffic toward Host-1. After the ingress routing decision, the traffic arrives at Leaf-2 in the context of the destination MAC-VRF, mac-vrf-1. Leaf-2 then performs a MAC lookup in mac-vrf-1 and forwards the frame to Host-1. Option D is therefore correct. Option A reverses the forwarding direction and misidentifies the leaf action. Option B incorrectly sends mac-vrf-2 traffic toward the IP-VRF on Leaf-2, even though Leaf-2 is acting as the egress PE for Host-1. Option C is also incorrect because the egress forwarding action is based on the MAC table in the destination MAC-VRF, not an IP-VRF ARP lookup at that stage. Reference: asymmetric L3 EVPN IRB data-plane operation, ingress routing and egress MAC forwarding.

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

The exhibit describes an EVPN IRB environment where MAC-VRF100 and IP-VRF-100 exchange host reachability through local learning and EVPN advertisements. Leaf-1 can advertise EVPN route type 2 updates containing host MAC/IP information for MAC-VRF100. This is the normal mechanism used to distribute endpoint bindings learned from local hosts. If IP-VRF-100 is not configured for prefix advertisement, Leaf-1 will not generate EVPN route type 5 updates for that IP-VRF, so option A is consistent. The ARP cache in the IP-VRF is normally required for local subnet host resolution; remote host reachability can be learned through EVPN rather than requiring every remote ARP entry to be learned by local data-plane ARP. Option B is false because ARP/GARP snooping is not performed by the IRB interface in the manner stated. ARP/GARP learning for proxy ARP and MAC/IP advertisement is associated with the MAC-VRF bridge-domain behavior and the local access side, not with the IRB subinterface indiscriminately snooping all ARP/GARP messages as described. Reference: EVPN IRB operation, RT-2 host MAC/IP advertisement, RT-5 behavior, ARP/GARP learning scope.

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

This setup represents a Layer 2 EVPN multi-homing attachment where the host is connected to Leaf1 and Leaf2 through an Ethernet Segment named ES-1. In SR Linux EVPN multi-homing, the Ethernet Segment must be associated with the physical or logical attachment interfaces facing the host. This allows the PEs to advertise Ethernet Segment information into EVPN, participate in DF election, and apply the appropriate forwarding behavior for single-active or all-active redundancy. Option D is therefore correct. Option A is not necessarily true because the exhibit indicates an active/standby style attachment, not all-active operation. Option B is also incorrect because ECMP on the remote MAC-VRF is not the mechanism that defines the local ES association or single-active behavior. Option C is wrong in this setup because a host LAG is required for common all-active L2 multi-homing with LACP, but the shown design uses an active/standby-style attachment where the Ethernet Segment is bound to the host-facing ports. The technical anchor is that ES-1 must be associated to the access ports connecting the host into the multi-homed MAC-VRF service. Reference: L2 EVPN multi-homing, Ethernet Segment interface association, DF behavior.

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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.

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