Cisco 300-640 Exam With Confidence Using Practice Dumps

Extended Power Capacity is specifically designed to increase usable power in a Cisco UCS X-Series chassis while the chassis remains configured in a redundant power mode. Cisco states that enabling Extended Power Capacity permits the chassis to borrow power capacity from the supplies reserved for redundancy, thereby increasing the total power that can be allocated to workloads.

Cisco provides a six-PSU example in Grid redundancy mode. Without Extended Power Capacity, the workload is capped at 8,400 W. Enabling the feature increases the available workload capacity to approximately 9,660 W—an increase of 15 percent—while retaining the configured redundant power mode.

Power capping in option A would restrict consumption rather than make additional power available. Adding more PSUs is impossible when the chassis already contains its supported complement of six supplies. Disabling Extended Power Capacity would reduce rather than increase the available power envelope.

This feature is particularly useful after installing additional accelerator, PCIe, memory, or compute resources that raise chassis power demand. It should nevertheless be applied within the data center's electrical and thermal design limits.

Study Guide Reference: AI Infrastructure Operations and Troubleshooting — UCS X-Series chassis power policy, redundancy, Extended Power Capacity, and capacity management.

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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.

The server contains six 3000-W supplies and must preserve N+2 redundancy . A 4,500-W workload requires two actively supplying PSUs because a single 3000-W supply cannot support the current load. Maintaining N+2 redundancy requires two additional PSUs to remain available beyond those required for the workload. The minimum operational complement is therefore four supplies: two supporting the power demand plus two retained for redundancy.

With six PSUs physically installed, the remaining two PSUs can be placed into standby , making option C correct.

The calculation is:

Required active capacity = ceiling(4500 W ÷ 3000 W) = 2 PSUs

Required redundancy = 2 PSUs

Minimum available PSUs = 2 + 2 = 4

Installed PSUs = 6

Eligible for standby = 6 − 4 = 2 PSUs

Power Save Mode is intended to reduce conversion losses when installed PSU capacity exceeds current demand. Cisco uses the same operating principle in UCS power management: additional supplies that are not needed to satisfy both the requested power budget and configured redundancy can be placed into power-saving operation.

Placing three supplies into standby would leave only three available supplies, violating the N+2 requirement for a workload requiring two PSUs.

Study Guide Reference: AI Infrastructure Operations and Troubleshooting — power efficiency, PSU redundancy, Power Save Mode, and UCS AI server power management.

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