300-420 Exam Dumps - Cisco CCNP Enterprise Questions and Answers

BFD is the correct design feature for detecting a link failure within 200 ms or less without materially increasing OSPF control-plane load. Cisco uses Bidirectional Forwarding Detection as a fast, lightweight failure-detection protocol that can be associated with routing protocols such as OSPF. Instead of relying on aggressive OSPF hello and dead timers, BFD performs rapid forwarding-path checks and notifies OSPF when the path fails. This allows fast convergence while avoiding the additional routing-protocol overhead and instability that can come from very low hello timers. UDLD detects unidirectional Layer 2 fiber failures, but it is not the routing adjacency failure-detection mechanism requested here. Carrier delay can adjust interface state transition timing, but it does not provide a routing-protocol independent liveness session. Fast hellos can reduce detection time, but they increase protocol traffic and can affect overall performance. BFD is therefore the proper design choice for fast and efficient OSPF convergence. Reference topics: BFD, OSPF convergence, fast failure detection, routed campus resiliency, control-plane efficiency.

PortFast is the correct functionality for the Gi1/0/1-10 interfaces when those ports are endpoint-facing access ports. Cisco spanning-tree design uses PortFast to allow edge ports to transition directly to the forwarding state, avoiding the normal listening and learning delay associated with traditional STP convergence. That improves user and endpoint connectivity after link-up events and is especially important for workstations, phones, printers, and access devices that should not participate in the Layer 2 topology. Root guard and BPDU guard are protection features, not the primary convergence optimization requested by the architect. UplinkFast was used in older STP designs to accelerate recovery for access switches with redundant uplinks, but it is not the edge-port functionality for interfaces Gi1/0/1-10. In a modern design, PortFast should be enabled only on true host-facing ports, normally together with BPDU guard to protect against accidental switch attachment. If the exhibit shows these interfaces as end-user access ports, PortFast is the feature that follows the recommendation to optimize STP convergence time. Reference topics: STP PortFast, edge-port convergence, BPDU guard, Layer 2 campus design.

The SD-Access underlay must run a routing protocol to establish IP connectivity between infrastructure devices. Cisco SD-Access uses a routed underlay to provide basic reachability among fabric edge nodes, border nodes, control-plane nodes, and intermediate nodes. Cisco design documentation states that all network elements in the fabric underlay must have IP connectivity through routing. Catalyst Center LAN Automation commonly deploys IS-IS for this purpose, although the underlay can be built manually with another supported routing design. The user endpoints and client subnets are not part of the underlay; they belong to the overlay, where fabric services, segmentation, and policy are applied. CEF should not be disabled, because efficient IP forwarding is necessary for the routed underlay. Two or more switches are not required merely to avoid spanning-tree loops; the SD-Access underlay is normally Layer 3 routed and avoids large Layer 2 loop domains. Reference topics: Cisco SD-Access underlay, routed access, LAN Automation, IS-IS, fabric node reachability.

Traffic shaping is required in the parent policy when hierarchical QoS uses CBWFQ in the child policy for low-bandwidth remote sites. In Cisco hierarchical QoS, the parent policy commonly shapes outbound traffic to the real available rate of the WAN service, especially when the physical interface speed is higher than the provider committed rate. The child policy then applies class-based queuing, such as CBWFQ and LLQ, inside the shaped rate. This structure creates an artificial congestion point on the router so the child queues can schedule packets predictably instead of allowing the provider to drop traffic after it exceeds the service rate. Policing in the child policy would drop excess packets and is not the normal prerequisite for nested CBWFQ. CBWFQ is supported in child policies within hierarchical designs, and parent shaping is the mechanism that makes the hierarchy effective. This is especially important on low-bandwidth WAN links where voice, video, and business-critical applications require deterministic treatment. Reference topics: hierarchical QoS, CBWFQ, parent shaping, child queuing, WAN QoS design.

Dual stack is the migration topology that supports IPv6 while preserving existing IPv4 services during the transition. In a dual-stack design, hosts and network devices run IPv4 and IPv6 in parallel, allowing applications and services to move gradually from IPv4 to IPv6 without forcing an immediate cutover. That matches the customer’s plan: keep the current IPv4 topology and services, introduce IPv6 connectivity, migrate services, and eventually decommission the IPv4 topology. 6VPE is used to carry IPv6 VPN routes across an MPLS IPv4 provider core, which is a service-provider VPN use case rather than a general enterprise migration topology. 6to4 is an automatic tunneling mechanism and is not appropriate as a stable enterprise migration plan. NAT64 enables IPv6-only clients to reach IPv4 resources through translation, but it does not preserve the complete IPv4 topology while services migrate. Cisco migration guidance treats dual stack as the cleanest operational model when infrastructure supports both protocols, because it avoids translation side effects and allows DNS and application behavior to determine which protocol is used.

The branch router should advertise the local LAN with the EIGRP network command and make the LAN-facing interface passive. A passive interface allows the connected network to be included in EIGRP advertisements while suppressing EIGRP hello packets and neighbor formation on that interface. This is exactly what the engineer needs: remote EIGRP neighbors learn the LAN subnet, but unnecessary multicast EIGRP messages are not sent onto the user LAN where no EIGRP neighbors should exist. Replacing EIGRP with a static default route would not meet the requirement to advertise the local LAN through EIGRP. Redistributing connected routes can work, but it is less clean for a simple LAN interface and can introduce external-route behavior or policy complexity. Advertising the subnet as a stub network does not suppress multicast hellos on the LAN interface by itself. Cisco design best practice is to use passive interfaces on LAN-facing interfaces that should be advertised but should not form routing adjacencies. Reference topics: EIGRP passive interface, network statements, branch routing, unnecessary neighbor prevention, multicast control traffic.

Dial-In: collector initiates a session to the device; supports gRPC only. Dial-Out: device initiates a session to the collector; supports TCP, UDP, and gRPC.

Model-driven telemetry can operate in dial-in or dial-out mode, and the distinction is based on which side initiates the session and how the subscription is established. In dial-in telemetry, the collector initiates a session to the network device and dynamically subscribes to the required sensor paths. This is useful when the collector wants direct control over the subscription lifecycle. Cisco telemetry documentation commonly associates dial-in with gRPC-based dynamic subscriptions on supported platforms. In dial-out telemetry, the device initiates the session toward the collector based on a configured subscription. The subscription exists in the device configuration, and the device streams telemetry data to the configured destination without requiring the collector to start the connection. This design is useful when devices are behind NAT, firewalls, or operational models where the network device should push telemetry to a known collector. Therefore, the mapping is: dial-in equals collector-initiated and gRPC-only in this context; dial-out equals device-initiated and supports the listed transport options. This distinction is central to Cisco model-driven telemetry design.

Static routes tied to IP SLA with a floating static backup route provide the cleanest active/standby design for this requirement. The MPLS L3VPN path is the primary connection and should carry traffic while it is available. IP SLA can actively test reachability across the primary path, and object tracking can remove the primary static route if the test fails. The backup IPsec VPN route is configured with a higher administrative distance, so it remains inactive until the primary route is withdrawn. This design is deterministic and prevents traffic from using the backup tunnel during normal operation. Running EIGRP across both paths could allow dynamic path selection, but it would require careful metric manipulation and could still introduce unintended failover behavior. BGP multipath is the opposite of the requirement because it is designed to install multiple paths simultaneously for load sharing. OSPF passive-interface on the backup connection would prevent neighbor formation rather than provide reliable backup routing. For a branch with one primary MPLS path and one backup IPsec path, tracked static routing with IP SLA is the appropriate design.

The correct routing design is OSPF with multiple areas. The company is moving away from RIP because the network has grown and now requires segmentation, summarization, fast convergence, and scalability. Cisco positions OSPF as a link-state IGP suitable for larger enterprise networks, and OSPF areas are the standard mechanism for containing topology information and scaling the link-state database. Area Border Routers can summarize routes between areas, reducing routing table size and limiting the scope of link-state flooding and SPF recalculation. This directly satisfies the requirement to segregate departments while summarizing between segments. EIGRP can converge quickly and summarize, but “stub areas” are not an EIGRP construct; EIGRP uses stub routers. OSPF virtual links are not a primary segmentation design tool; they are used to repair backbone connectivity issues. Modifying EIGRP K values changes metric calculation but does not solve segmentation or summarization. Reference topics: OSPF multi-area design, ABR summarization, SPF scope control, enterprise IGP scalability.

The correct model set is the one that configures the IOS XE interface GigabitEthernet2/1/0 with IPv4 address 10.10.10.10 and prefix length 27 using valid XML according to the selected YANG schema. The directly connected host address 10.10.10.1/27 confirms the subnet relationship; both addresses belong to 10.10.10.0/27, so the interface configuration must use that prefix length rather than a host mask or an unrelated network. YANG-based configuration is strict: the namespace, container hierarchy, interface type, interface name, and address fields must match the device model. If an option places GigabitEthernet under the wrong container, represents the mask incorrectly, or uses a schema from a different model family, the device will reject the payload or configure the wrong object. Option D correctly represents the IOS XE XML structure and the required addressing. In real operations, the engineer should follow this with a get-config readback against the running datastore to prove that the structured configuration committed as intended. Reference topics: IOS XE interface YANG, XML payload structure, NETCONF configuration, IPv4 subnet validation.