Free Practice Questions for NVIDIA NCP-AIN Exam

To upgrade the MLNX-OS on InfiniBand switches, the recommended procedure is as follows:​

Connect to the switch via SSH: Establish a secure shell connection to the switch using its management IP address.​

Fetch the MLNX-OS software image: Obtain the appropriate MLNX-OS software image from the official source or repository.​

Use the 'install' command to perform the upgrade: Execute the 'install' command on the switch to initiate the upgrade process with the fetched software image.​

This method ensures a smooth and efficient upgrade without the need for physical intervention or service disruption.​

Reference Extracts from NVIDIA Documentation:

"Click on Systems → MLNX-OS Upgrade. Select the desired upgrade method (e.g. 'Install from local file'). Select your image and click 'Install Image'."

The "What Just Happened" (WJH) service on Cumulus switches provides real-time visibility into network problems by monitoring various layers and components, including layer 1, layer 2, layer 3, tunnel, buffer, and Access Control List (ACL) related issues. WJH streams detailed and contextual telemetry data, enabling administrators to diagnose and troubleshoot network problems effectively.​

Reference Extracts from NVIDIA Documentation:

"WJH can monitor layer 1, layer 2, layer 3, tunnel, buffer and ACL related issues."​

"The WJH service enables you to diagnose network problems by looking at dropped packets."​

To identify the activeSubnet Manager (SM)node in an InfiniBand fabric, the correct command sequence is:

sminfo

Displays general information about the active SM in the fabric, including itsLID.

smpquery ND <LID>

Resolves theNode Description (ND)at the given LID, revealing the exact hostname or label of the SM server.

From the InfiniBand Tools Guide:

"The sminfo utility provides the LID of the master SM. Use smpquery ND <LID> to resolve the node name hosting the SM."

This two-step approach is standard for locating and validating the SM identity in fabric diagnostics.

Incorrect Options:

B (Nl)is an invalid query type.

CandDdo not identify SMs.

NetQintegrates multiple telemetry sources, includingWJH,DOCA, and notably,Behavioral Telemetry.

From theNetQ Documentation – Behavioral Telemetry Section:

"Behavioral telemetry in NetQ correlates server and application behavior with network events, offering insights into root cause analysis by detecting anomalies in protocol, path, or performance behavior."

This helps identify patterns like:

Misbehaving applications causing retransmits.

Sudden changes in traffic flows.

Latency spikes correlated with app-level issues.

It complements device-level telemetry by introducingintent-based anomaly detection, crucial for proactive operations.

Incorrect Options:

Flow telemetryandpacket captureoffer raw data but not behavioral insights.

Application telemetryis too vague and is not the term NetQ uses for this feature.

Inmulti-subnet InfiniBand environments, AI training clusters are segmented across network zones (or subnets). Direct GPU-to-GPU communication (especially for collective ops like AllReduce, Broadcast, etc.) requires inter-subnet reachability. NCCL supports this via theInfiniBand Router (IB Router)feature.

From theNCCL User Guide – Environment Variables Section:

"NCCL_IB_USE_IB_ROUTER: Enables NCCL support for IB routers which are used in multi-subnet InfiniBand fabrics. When enabled, NCCL can traverse IB subnets using a properly configured IB router."

This is critical because without IB Router support:

NCCL would be restricted to intra-subnet GPU collectives.

Multi-node training across subnets would fail or fall back to slower TCP fallback mechanisms.

Technical Explanation:

IB Routers usesubnet managers(like OpenSM with routing tables) to bridge communication across different InfiniBand partitions.

NCCL queries the subnet topology, discovers routing paths, and usesRDMA CM(Connection Manager) to establish GPU transport over routers.

This capability is especially important in data center-scale AI clusters spanning multiple racks or zones, connected viaIB routers like Mellanox SB7800 or QM8700 series.

When NCCL_IB_USE_IB_ROUTER=1 is set:

NCCL includes router-aware route resolution in its path selection logic.

Enables efficientzero-copy communicationacross GPUs in different IB domains, maintaining low latency.

Other Options Explained:

A. Lazy connection establishment– controls when peer connections are made but does not enable cross-subnet reach.

B. GPU Direct RDMA– enables intra-node direct memory access, not applicable for routing across subnets.

C. Static plugin linking– affects how NCCL links plugins, not related to IB topology.

Exact Extract Reference:

Source: NVIDIA NCCL User Guide – Environment Variables Section

Extract: "NCCL_IB_USE_IB_ROUTER: Enables NCCL support for IB routers, required for multi-subnet InfiniBand configurations. Ensures proper routing of collectives over fabric-wide topologies."

In the Spectrum-X architecture,BlueField-3 SuperNICsare responsible for executing the congestion control algorithm. They handle millions of congestion control events per second with microsecond reaction latency, applying fine-grained rate decisions to manage data flow effectively. This ensures optimal network performance by preventing congestion and packet loss.​

The SN5600 smart-leaf/spine/super-spine switch offers 64 ports of 800GbE in a dense 2U form factor. The SN5600 offers diverse connectivity in combinations of 1 to 800GbE and boasts an industry-leading total throughput of 51.2Tb/s.​

For optimal performance in multi-node, multi-GPU AI workloads:

NVLinkprovides high-speed, low-latency communication between GPUs within the same node.

InfiniBandoffers efficient, scalable communication between nodes in a data center.Combining these technologies ensures both intra-node and inter-node communication needs are effectively met.​

NVIDIA NetQ is a comprehensive network operations tool designed to provide real-time visibility into the health and performance of NVIDIA networking environments, including Spectrum-X. It offers detailed telemetry and analytics, allowing administrators to monitor adaptive routing behaviors, detect congestion, and analyze traffic patterns. By leveraging NetQ, you can ensure that adaptive routing is functioning as intended and that the network is optimized for AI workloads.​

Reference Extracts from NVIDIA Documentation:

"The NVIDIA NetQ network validation and ASIC monitoring tool set provide visibility into the network health and behavior. The NetQ flow telemetry analysis shows the paths that data flows take as they traverse the network, providing network latency and performance insights."​

"By leveraging telemetry from Spectrum Ethernet switches and BlueField-3 SuperNICs, NVIDIA NetQ can detect network issues proactively and troubleshoot network issues faster for optimal use of network capacity."​