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

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

For Layer 2 data center interconnect using an integrated gateway, VPLS 100 on the Nokia 7750 SR represents the WAN-side Layer 2 VPN service. The VPLS requires an EVI because EVPN uses the EVI to identify the L2 service instance in the control plane. It also requires BGP EVPN signaling with the appropriate route targets so the local and remote service instances can import the correct EVPN routes. Because the service is transported across the WAN, the BGP/EVPN instance must be associated with the MPLS transport tunnels toward the remote gateway, dcgw20. A VXLAN instance with a VNI is not configured in the 7750 SR VPLS 100 for this integrated WAN gateway service. The VXLAN/VNI mapping is used inside the SR Linux data center fabric where MAC-VRF services are transported over VXLAN. On the WAN side, the VPLS service is carried using MPLS/EVPN mechanisms, not a VXLAN VNI configured directly under the VPLS. Reference: integrated gateway DCI, L2 EVPN/VPLS interworking, EVI and route-target 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]:

The exhibit describes a Layer 3 multi-homing scenario where the Ethernet Segment is associated with an IP-VRF and the configuration references an EVI value of 1000. The segment is configured with all-active multi-homing, allowing multiple attached leaf routers to advertise reachability for the same external L3 next-hop or third-party prefix attachment. In this model, the Ethernet Segment represents the shared L3 attachment and is used by EVPN to associate remote prefix reachability with the multi-homed segment. The incorrect statement is that a LAG must be configured on the connected leaf routers and the host. That requirement is specific to many Layer 2 all-active host attachment designs, where the host commonly uses LACP toward multiple leaf routers and the leaf LAG subinterfaces are associated with the Ethernet Segment. In Layer 3 multi-homing, the attached device can be a router or VNF, and the EVPN ES association can be used for L3 prefix reachability without mandating that the host side be configured as a LAG. Reference: L3 EVPN multi-homing, EVI association, all-active Ethernet Segment 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]:

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]:

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]:

When Leaf-1 receives an ARP request from Host-1, it learns the source MAC address in the local MAC table and learns the source IP/MAC binding in the proxy ARP table. For EVPN distribution, the relevant control-plane advertisement is an EVPN route type 2 MAC/IP advertisement containing Host-1's MAC and the actual host IP address, 192.168.100.1. This allows remote PEs to populate their EVPN-derived forwarding and proxy ARP state with the correct endpoint binding. Option A is false because advertising the host MAC with the IP address set to 0.0.0.0 does not represent the learned MAC/IP binding required for proxy ARP synchronization. A MAC-only RT-2 advertisement may exist in EVPN contexts, but the question specifically states that Leaf-1 has learned the MAC/IP binding through ARP and is distributing that information. Therefore, the valid advertisement must include the real host IP address. Remote PEs use the MAC/IP route to learn the endpoint, not an all-zero IP placeholder for this proxy ARP learning event. Reference: EVPN RT-2 MAC/IP advertisement, proxy ARP table population, endpoint synchronization.

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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 an integrated gateway-based DCI design, the same physical or logical router performs both the data center gateway role and the WAN PE role. This is why option D is correct. The device terminates or participates in the data center-side EVPN service and also handles the WAN-side VPN transport, including route translation or re-advertisement where needed. This approach avoids exposing every data center leaf router to the WAN and avoids requiring route reflector reachability between data centers. It also avoids building VXLAN tunnels directly between all leaf routers in separate data centers. Those characteristics belong to gateway-less DCI, where the EVPN overlay stretches more directly across the WAN and the WAN must carry the underlay or overlay reachability required by the data center leaves. Integrated gateway design is more controlled: the gateway is the interworking point, which makes it suitable when the provider or operator wants a strong service boundary and centralized DCI policy enforcement. Reference: integrated gateway-based DCI, single-router gateway/WAN PE function, EVPN/VPN interworking.

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

PE-CE routing is the mechanism used to exchange customer prefix reachability between a provider edge or data center leaf and the attached customer edge router. It can be implemented statically or dynamically. Static routing is operationally simple but does not scale well when many prefixes or frequent changes are involved. BGP is preferred for larger deployments because it supports policy, route filtering, attributes, and automated advertisement of changing reachability. In most EVPN PE-CE designs, eBGP is preferred because it creates a clean routing boundary between the PE and CE, with each device operating in a different autonomous system. Option D is false because the CE does not advertise BGP EVPN route type 5 updates to the PE. The CE advertises ordinary IPv4 or IPv6 unicast prefixes over the PE-CE routing session. The PE then imports those customer prefixes into the IP-VRF and advertises them into the EVPN overlay as route type 5 IP Prefix routes toward other PEs. This distinction matters: EVPN signaling is a PE-to-PE overlay function, not a CE-originated EVPN control-plane role. Reference: PE-CE routing, eBGP, EVPN RT-5 prefix advertisement.

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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]:

An IRB interface provides the logical L3 gateway function between a Layer 2 MAC-VRF and a Layer 3 IP-VRF on the same PE. It allows locally bridged hosts to route into the tenant IP-VRF while preserving EVPN control-plane signaling for MAC/IP reachability. The IRB subinterface must have at least one IP address because it acts as the routed gateway for the subnet, and it may also be configured with ACLs to apply traffic policy at the L3 boundary. Option B is false because it incorrectly generalizes the IRB relationship. In SR Linux EVPN service modeling, an IRB subinterface connects a MAC-VRF to an IP-VRF in a controlled one-to-one service attachment context; the design is not that both IP-VRFs and MAC-VRFs arbitrarily contain multiple IRB interfaces for the same relationship. A MAC-VRF has its IRB gateway association into the IP-VRF, and the IP-VRF may connect to multiple MAC-VRFs through distinct IRB contexts, but the statement as written is not the correct rule for IRB interface behavior. Reference: SR Linux IRB interface operation, MAC-VRF/IP-VRF interconnection, gateway IP and ACL support.

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

For Layer 2 all-active EVPN multi-homing on SR Linux, the Ethernet Segment configuration is the control-plane anchor that binds the redundant access attachment to EVPN. The relevant LAG subinterfaces must be associated with the Ethernet Segment so that the PE can advertise the segment correctly and apply split-horizon and aliasing behavior. The Ethernet Segment must also be administratively enabled; otherwise, the PE will not participate properly in ES discovery and DF procedures. The multi-homing mode must be set to all-active to permit forwarding through multiple attached leaf routers and support host-side LAG operation. The false statement is option B. The Ethernet Segment Identifier has a defined structure, and the blanket statement that the 2nd through 7th octets “must not be all zeros” is not a valid requirement as stated. What matters operationally is that the ESI uniquely identifies the same multi-homed Ethernet Segment across participating PEs and is consistently configured where required. The ESI must be non-zero as a meaningful segment identifier, but the specific octet restriction in the option is not the SR Linux all-active configuration rule. Reference: SR Linux L2 EVPN all-active multi-homing, Ethernet Segment configuration, LAG association.

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