Free Cisco 400-007 Practice Exam with Questions & Answers | Set: 9

B (MST — Multiple Spanning Tree): Bundles multiple VLANs into fewer STP instances, minimizing the scope of TCN propagation, which helps reduce MAC table flushing and unicast flooding.

Why other options are incorrect:

A: PVRSTP still processes TCNs per VLAN, increasing flooding.

C: Legacy STP behaves similarly but is not optimized for multiple VLANs.

D: PVSTP+ generates TCNs per VLAN like PVRSTP.

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When data center fabrics are extended across multiple private and public clouds, as in hybrid or multi-cloud designs, enterprises benefit from:

C. Ability to place workloads across clouds: Application and workload mobility is a key outcome of interconnected data center fabrics. It supports disaster recovery, scaling, and cost optimization strategies.

D. Centralized visibility: Modern SDN/cloud-integrated platforms offer centralized control and monitoring across domains, giving IT teams end-to-end insight regardless of workload location.

These principles support the CCDE v3.1 goals for cloud-aligned architecture, which promotes flexibility, operational simplicity, and global-scale services.

Why other options are incorrect:

A: Enhanced security is a benefit but not guaranteed simply by interconnecting clouds; it depends on the actual security controls in place.

B: Cloud deployments may compromise data and network ownership, especially in public models.

E: Cloud mobility is typically bidirectional when fully designed; unidirectional behavior is limiting and not an intended design goal.

Comprehensive and Detailed Explanation:

A: PaaS (Platform as a Service) solutions often introduce strong vendor-specific APIs, services, and tooling, making it difficult to migrate applications later—leading to vendor lock-in.

Other options:

B and C apply more to SaaS and IaaS models.

D: Multi-tenant security concerns are common in all models but not unique or predominant in PaaS.

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C. Fragment data packets: On slow WAN links, large data packets can delay small voice packets (serialization delay). Fragmentation ensures that voice packets are interleaved and not delayed behind large data frames (Link Fragmentation and Interleaving - LFI).

E. Prioritize voice packets: QoS mechanisms (LLQ, priority queuing) ensure that voice traffic is serviced first, reducing jitter and delay.

These are both critical QoS design principles for real-time application performance in constrained branch WAN scenarios, as outlined in CCDE v3.1.

Why other options are incorrect:

A: Increasing bandwidth may help but doesn’t address serialization or prioritization.

B: Memory upgrades do not directly improve voice quality.

D: Fiber upgrades do not address WAN-specific serialization or QoS.

D (Lifecycle model):The lifecycle model aligns directly with traditional project management (such as Waterfall). It follows a sequential, phase-driven process: requirement gathering, design, implementation, testing, and maintenance. Each phase must be completed before moving to the next, with defined milestones and documentation.

Other options explained:

A: "Static model" is not a standard recognized development model.

B: Agile is iterative and adaptive, opposite of traditional models.

C: Evolutionary delivery is more incremental, not fully aligned with traditional models.

A (Change OSPF reference bandwidth): OSPF calculates path cost based on interface bandwidth using a formula where cost = reference bandwidth / interface bandwidth. The default OSPF reference bandwidth is 100 Mbps, which causes all faster links (1 Gbps and above) to appear with the same minimum cost.

Updating the reference bandwidth (e.g., to 10000 or higher) allows OSPF to assign accurate costs to faster links, enabling proper path selection that reflects real link capacities.

Other options explained:

B: Filtering is not the correct method for path optimization.

C: Changing interface bandwidth values is a workaround but not scalable or recommended compared to updating the reference bandwidth globally.

D: Summarization addresses prefix aggregation, not cost calculation.

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B (Communicates desired behavior to controllers):In SDN architecture, the application layer contains business logic and network applications that request services or behaviors from the controller through northbound APIs.

Other options explained:

A: Refers to the controller’s role in collecting network status.

C: Refers to data plane (switches/routers) handling packet forwarding.

D: Misrepresents control plane-controller interaction.

A (DAI - Dynamic ARP Inspection): Prevents ARP spoofing attacks on the data plane.

B (IP Source Guard): Prevents IP address spoofing by verifying IP/MAC bindings against DHCP snooping tables.

Both are directly applied to securing the data plane (traffic forwarding layer).

Why other options are incorrect:

C (BEEP): A transport protocol, not a data plane security feature.

D (CPPr): Protects the control plane, not data plane.

E (MPP): Protects management plane, not data plane.

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B (Confidentiality):Protects data from unauthorized access or disclosure.

E (Integrity):Ensures data remains accurate and unaltered.

F (Availability):Ensures that data and systems are accessible when needed.

Other options explained:

A: Cryptography is a tool used to achieve confidentiality, integrity, or authentication, but it's not part of the CIA triad itself.

C/D: Authorization and identification are security processes, but not part of the core CIA triad.

In DMVPN designs with many spokes, spokes may fail to receive periodic keepalives or routing updates if queues overflow during congestion, causing holding timers to expire and tunnels to flap. Increasing the hold queue size on the tunnel interface of the spoke routers allows them to buffer control plane packets during congestion and avoid premature tunnel teardown.

Why other options are incorrect:

A, C, E: Physical interface queues do not directly affect tunnel protocol timers.

D: QoS may help prioritize control plane traffic but doesn't address queue depth directly, which is the root cause of the issue.

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