Free Cisco 300-640 Practice Exam with Questions & Answers | Set: 2

Cisco Nexus 9000 integration with NVIDIA adaptive-routing capabilities requires the Nexus switch to enable the Spectrum-X hardware profile . Cisco's current NX-OS configuration guide explicitly specifies the global configuration command hardware profile spectrum-x to enable NVIDIA Spectrum-X adaptive routing. When a Nexus switch peers with a supported NVIDIA NIC, this capability allows the NIC to handle packet reordering created by granular techniques such as per-packet Dynamic Load Balancing.

This is particularly important for AI training because large synchronized RDMA flows can create uneven utilization under conventional hash-based ECMP. Cisco explains that per-packet DLB can spray packets over multiple paths and that NVIDIA adaptive routing/direct data placement enables the receiver to correctly handle packets that arrive out of order, improving utilization and collective-operation performance.

Option A is not the documented NX-OS configuration syntax. Option B is not the Cisco-prescribed Nexus integration command. Option D may be relevant to traffic classification in other designs but does not activate Spectrum-X adaptive-routing interoperability.

Therefore, the Cisco-documented configuration is C. This differs from the supplied file's marked answer B.

Study Guide Reference: 3.0 AI Infrastructure Deployment and Data Management — 3.1.d Load distribution.

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Data Center Quantized Congestion Notification, or DCQCN, combines ECN-based end-to-end congestion signaling with Priority Flow Control to maintain efficient and effectively lossless RoCE transport. Cisco states that ECN reacts first , while PFC functions as a safety mechanism if congestion escalates faster than endpoint rate control can respond. With moderate queue buildup, WRED marks ECN-capable packets. If queue utilization continues toward critical levels, PFC pauses the affected priority before packet loss occurs.

The second statement in option C is also correct. When the receiving host receives a RoCEv2 packet carrying the ECN Congestion Experienced marking, the receiving endpoint generates a Congestion Notification Packet, or CNP, toward the transmitting source. The source then reduces its transmission rate according to the congestion-control algorithm.

The network switch performs the ECN marking but does not generate the RoCE CNP on behalf of the receiver. This eliminates options A, B, and D. Options A and D additionally reverse the normal operational sequence by claiming that PFC responds before ECN.

The distinction is important because efficient AI fabrics seek to manage congestion proactively through ECN while reserving PFC for severe congestion and microbursts.

Study Guide Reference: 3.1.a Congestion control mechanisms — PFC and ECN; 3.1.b RoCEv2.

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GPU Utilization and GPU Performance are the two choices that directly measure the behavior of accelerator resources used by AI workloads. GPU utilization indicates how actively the accelerator's computational resources are being consumed. Persistent low utilization can expose CPU, storage, networking, synchronization, or workload-scheduling bottlenecks, while sustained high utilization generally indicates effective use of expensive GPU capacity.

Cisco Intersight is increasingly oriented toward AI-specific infrastructure visibility. Cisco states that Intersight provides actionable metrics for GPU performance , resource-utilization trends, and power efficiency. Its Metrics Explorer and monitoring capabilities provide deep telemetry for infrastructure resources, including AI accelerators.

Explorer and Monitor in options B and C represent interfaces or functional capabilities rather than the performance metrics requested by the question. System CPU Utilization is useful when determining whether a workload is host-CPU constrained, but it does not directly measure GPU performance or GPU utilization.

Accordingly, A and D are the two choices that correspond most directly to the stated objective of measuring GPU performance and utilization.

Study Guide Reference: AI Infrastructure Operations and Troubleshooting — monitoring GPU performance, utilization, resource bottlenecks, and Cisco Intersight telemetry.

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The UCS X210c M8 combined with the UCS X580p PCIe Node satisfies the complete requirement set. The X210c M8 uses Intel Xeon 6 processors, while the X580p provides modular GPU expansion and supports up to four PCIe GPUs. Cisco specifically positions this combination for generative AI, inference, and other GPU-accelerated workloads. Management is policy-driven through Cisco Intersight, providing the required cloud-based operational model.

The X580p also supports NVIDIA H200 NVL GPUs and NVLink Bridge capabilities. This is significant where low-latency communication is required between specific GPU pairs because NVLink provides substantially higher-bandwidth GPU-to-GPU communication than standard PCIe-only communication. Cisco's UCS ordering guidance specifies that H200 NVL supports NVL Bridge configurations with a minimum of two GPUs.

Options C and D are high-density AI systems, but they use AMD EPYC-based architectures rather than satisfying the stated Intel CPU requirement. Option A likewise does not match the specified X-Series composability, cloud-managed GPU resource model, and Intel-based requirement as directly as the X210c M8 configuration.

Study Guide Reference: 2.0 AI Infrastructure Components and Architecture — 2.2 Compute deployment; 2.4 power and efficiency considerations.

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backend network

frontend network

storage network

management network

Large AI environments normally separate traffic into purpose-built fabrics because GPU collective communication, storage I/O, application access, and infrastructure management have fundamentally different performance and availability characteristics. Cisco identifies the backend network as the east-west fabric dedicated to inter-GPU communication. It carries high-bandwidth RoCEv2/RDMA traffic associated with distributed training and must provide exceptionally low latency and lossless behavior.

The frontend network provides north-south connectivity between AI nodes and the wider data center, supporting application access, inference traffic, general data movement, logging, and other in-band services. The storage network connects compute nodes to shared datasets, model checkpoints, and high-performance parallel or distributed storage systems. Cisco AI POD designs may use dedicated storage-leaf connectivity to prevent storage traffic from interfering with backend GPU collective communication. The management network serves out-of-band management interfaces for servers, switches, storage platforms, and other infrastructure components. Cisco AI reference architectures explicitly distinguish backend, frontend/storage, and management connectivity for these purposes.

Maintaining these traffic domains independently improves deterministic performance, fault isolation, congestion control, security, and operational manageability.

Study Guide Reference: AI Infrastructure Components and Architecture — network fabrics, bandwidth, latency, scalability, and AI infrastructure connectivity.

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A rail-optimized topology is specifically engineered for large GPU clusters where collective communication performance and minimum inter-GPU latency are critical. In a rail-optimized design, corresponding GPU/NIC interfaces across compute nodes attach to the same rail switch. This allows communication between GPUs of the same rank to remain on a single leaf or rail switch whenever possible, eliminating unnecessary spine traversal and reducing network hops.

Cisco's AI/ML networking guidance gives a directly applicable design example: a rail-optimized, nonblocking architecture connecting 512 GPUs in 64 nodes, with eight GPUs per node . The design uses eight rail/leaf switches and four spine switches and maintains nonblocking bandwidth while optimizing GPU collective communication. Cisco explicitly states that rail-optimized design is recommended for NVIDIA GPU environments.

A conventional leaf-spine architecture can certainly provide high performance and nonblocking bandwidth, but option C is more specific to the requirement for the lowest possible GPU-to-GPU latency at this scale. Flat Layer 2 does not provide the required scalable fabric architecture, while a traditional three-tier model introduces additional hops and potential oversubscription.

Study Guide Reference: 2.0 AI Infrastructure Components and Architecture — 2.1 Evaluate network deployment based on bandwidth, latency, redundancy, scalability, and security.

RoCEv2 transports the InfiniBand transport protocol over UDP/IP, allowing RDMA traffic to traverse Layer 3 networks. The RDMA transport layer preserves packet-level sequencing, reliability, and ordering semantics that are inappropriate for arbitrary IP fragmentation. Consequently, RoCEv2 traffic is designed to traverse the network without IP fragmentation, making option D the intended technical answer. NVIDIA documentation confirms that RoCEv2 places the InfiniBand transport protocol behind UDP and IP rather than using the native InfiniBand network-layer header.

A consistent end-to-end MTU is therefore essential in GPU fabrics. AI clusters commonly use jumbo frames, and every switch interface, port channel, Layer 3 interface, and server NIC along the path must support the configured packet size. Unexpected fragmentation is incompatible with the deterministic behavior required by high-performance RDMA workloads.

Option A identifies a general IPv4 consequence of setting DF—Path MTU Discovery can use DF—but it is not the fundamental RoCE transport requirement tested here. Option B is incorrect because DF does not classify packets as RDMA. Option C is also incorrect because ECMP path selection is normally determined by packet-header hashing; the DF flag does not force packets onto a single path.

Study Guide Reference: AI Infrastructure Deployment and Data Management — RoCEv2, MTU design, lossless transport, and high-performance Ethernet.

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The thermal events are the strongest diagnostic indicator in the scenario and should direct troubleshooting toward the server's cooling environment before workload-level tuning . Excessive temperature can cause processor or accelerator thermal throttling, which directly produces intermittent performance degradation and latency spikes even when CPU, memory, GPU, and storage utilization otherwise appear normal.

Cisco's C-Series installation requirements emphasize correct airflow and specifically warn that obstructing server ventilation can cause overheating, higher fan speeds, and increased power consumption. Cisco's C885A M8 documentation, representative of modern AI-oriented UCS C-Series platforms, specifies twelve hot-swappable system fans for proper front-to-back cooling.

Therefore, the administrator should first inspect ambient temperature, cold-aisle/hot-aisle conditions, physical airflow, obstructions, and fan health. Any failed fan should be replaced promptly.

Option A is a sensible performance-analysis step when there is no stronger hardware fault indicator, but repeated thermal events make it secondary here. Storage inspection in option B is not supported by the symptoms. Option C focuses on power delivery, yet the event evidence specifically points toward thermal management rather than insufficient PSU capacity.

Troubleshooting should follow the fault evidence, beginning with the lowest-level physical condition that can explain the observed symptoms.

Study Guide Reference: AI Infrastructure Operations and Troubleshooting — UCS health monitoring, environmental faults, thermal conditions, and performance troubleshooting.

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