NCP-AIN Sample Questions Answers

Accessing theBlueField DPU Operating System (OS)is possible throughrshim, either over PCIe or USB, and viaSSH through the OOB interfacewhen in DPU mode.

From theNVIDIA BlueField Software Documentation:

"You can access the BlueField OS through the rshim interface. The rshim module enables host-to-DPU communication either via PCIe (default) or USB."

B. rshim over PCIe: Default when BlueField is installed in a host.

D. rshim over USB: Useful for provisioning or systems without PCIe drivers.

Incorrect Options:

A (NIC mode): BlueField acts as a transparent NIC; OS access is not available to the host.

C (Redfish): Redfish is for out-of-band management, not direct OS-level access.

The ibstat command is utilized to display the operational status of InfiniBand Host Channel Adapters (HCAs). It provides detailed information, including the state (e.g., Active, Down), physical state (e.g., LinkUp, Polling), and link layer (e.g., InfiniBand, Ethernet) of each port on the HCA. This information is crucial for diagnosing connectivity issues and ensuring that the InfiniBand interfaces are functioning correctly.​

Reference Extracts from NVIDIA Documentation:

"The ibstat command displays the status of the host channel adapters (HCAs) in your InfiniBand fabric. The status includes the HCAs' state, physical state, and link layer."​

"For proper operation, you are looking for ‘State: Active‘ and ‘Physical State: LinkUp’."​

MLNX-OS, the operating system for NVIDIA's networking devices, defines two primary user account types:adminandmonitor. Theadminaccount has full administrative privileges, allowing for complete configuration and management of the system. Themonitoraccount, on the other hand, is designed for users who need to view system configurations and statuses without making any changes. This separation ensures a clear distinction between users who manage the system and those who monitor its operations.​

Reference Extracts from NVIDIA Documentation:

"There are two user roles or account types: admin and monitor. As 'admin', the user is privileged to run all the available commands. As 'monitor', the user can run commands that show system configuration and status, or set terminal settings."​

MLNX-OS is the network operating system used on NVIDIA’s Mellanox Ethernet switches, including the Spectrum family (e.g., Spectrum-4 switches in the Spectrum-X platform), designed for high-performance Ethernet networking in AI and HPC data centers. MLNX-OS provides a command-line interface (CLI) for configuring and managing switch operations, with user accounts controlling access to various commands and functions. The question asks for the two general user account types in MLNX-OS, which define the primary privilege levels for user access.

According to NVIDIA’s official MLNX-OS documentation, the two general user account types in MLNX-OS are:

monitor: This account type has read-only access, allowing users to view configurations, status, and logs but not modify settings. It is used for monitoring and troubleshooting without risking unintended changes.

admin: This account type has full read-write access, enabling users to view and modify all configurations, execute commands, and manage the switch’s operations. It is intended for administrators with complete control over the system.

These two account types represent the primary privilege levels in MLNX-OS, providing a clear distinction between read-only monitoring and full administrative access.

Exact Extract from NVIDIA Documentation:

“MLNX-OS supports two primary user account types for managing switch operations:

monitor: Users with monitor privileges have read-only access to the system. They can view configuration details, system status, and logs but cannot make changes to the configuration.

admin: Users with admin privileges have full read-write access, allowing them to configure, manage, and troubleshoot all aspects of the switch, including executing privileged commands.These account types ensure secure and controlled access to the switch’s management functions.”—NVIDIA MLNX-OS User Manual

This extract confirms that options B (monitor) and C (admin) are the correct answers. These account types are the standard privilege levels in MLNX-OS, used to manage access for monitoring and administrative tasks on Spectrum switches, including those in Spectrum-X deployments.

NVIDIA's What Just Happened (WJH) is a feature that provides real-time visibility into network problems by analyzing all packets passing through the switch and alerting on performance issues caused by packet drops, congestion, high latency, or misconfigurations.

WJH retains the last packets that were dropped from the switch with complete packet headers and the actual drop reason. This enhances the ability to debug network problems, identify affected flows, and decrease time-to-repair.

The mlxlink tool is used to check and debug link status and issues related to them. The tool can be used on different links and cables (passive, active, transceiver, and backplane). It is intended for advanced users with appropriate technical background.​

FromNVIDIA Performance Tuning Guide (ib_write_bw Tool Usage):

"-S <SL>: Specifies the Service Level (SL) to use for the InfiniBand traffic. SL is used for setting priority and mapping to virtual lanes (VLs) on the IB fabric."

This flag is useful when testing QoS-aware setups or validating SL/VL mappings.

Incorrect Options:

A– No such flag for burst size.

B– -q defines number of QPs.

C– --rate or -R is used for rate-limiting.

The NVIDIA Spectrum-X networking platform is an Ethernet-based solution optimized for AI workloads, combining Spectrum-4 switches, BlueField-3 SuperNICs, and advanced software to deliver high performance and low latency. Gathering telemetry data is critical for optimizing Spectrum-X networks, as it provides visibility into network performance, congestion, and potential issues. The question asks for the tool used to collect telemetry data in a Spectrum-X network.

According to NVIDIA’s official documentation, NVIDIA NetQ is the primary tool for gathering telemetry data in Ethernet-based networks, including those running on Spectrum-X platforms with Cumulus Linux or SONiC. NetQ is a network operations toolset that provides real-time monitoring, telemetry collection, and analytics for network health, enabling administrators to optimize performance, troubleshoot issues, and validate configurations. It collects detailed telemetry data such as link status, packet drops, latency, and congestion metrics, which are essential for Spectrum-X optimization.

Exact Extract from NVIDIA Documentation:

“NVIDIA NetQ is a highly scalable network operations tool that provides telemetry-based monitoring and analytics for Ethernet networks, including NVIDIA Spectrum-X platforms. NetQ collects real-time telemetry data from switches and hosts, offering insights into network performance, congestion, and connectivity. It supports Cumulus Linux and SONiC environments, making it ideal for optimizing Spectrum-X networks by providing visibility into key metrics like latency, throughput, and packet loss.”

—NVIDIA NetQ User Guide

This extract confirms that option C, NetQ, is the correct tool for gathering telemetry data in a Spectrum-X network. NetQ’s integration with Spectrum-X switches and its ability to collect and analyze telemetry data make it the go-to solution for network optimization tasks.

AnInfiniBand (IB) Routerconnects two or moreInfiniBand subnets, making it possible for nodes in different subnets to communicate throughroute-managed communication.

From the officialNVIDIA InfiniBand Routers Documentation:

"An InfiniBand router provides connectivity between two or more InfiniBand subnets, enabling communication between hosts that are not on the same subnet while preserving isolation and scalability."

Ensures fabric scalability by allowing subnet segmentation.

Uses LID routing across subnet managers (SMs).

Essential in large clusters with thousands of nodes.

Incorrect Options:

AandBare incorrect: InfiniBand does not connect directly to Ethernet or SANs without a gateway.

Cis unrelated: NVLink is a GPU interconnect, not tied to InfiniBand routers.

NVIDIA AIR (AI-Ready Infrastructure) is a cloud-based simulation platform designed to model and validate data center network deployments, including Spectrum-X Ethernet networks, using realistic topologies and configurations. When creating a custom topology in NVIDIA AIR, users can define network links between devices (e.g., spine and leaf switches) using a DOT file format, which is based on the Graphviz graph visualization software. The question asks for the correct syntax to define a link between port 1 on a spine switch (spine-01) and port 41 on a leaf switch (gpu-leaf-01) in a NVIDIA AIR simulation.

According to NVIDIA’s official NVIDIA AIR documentation, the DOT file format is used to specify network topologies, including nodes (devices) and links (connections between ports). The syntax for defining a link in a DOT file uses a double dash (--) to indicate a connection between two ports, with each port specified in the format "":"". For Spectrum-X networks, which typically use Cumulus Linux or SONiC on NVIDIA Spectrum switches, ports are commonly labeled as swpX (switch port X) rather than ethX (Ethernet interface), especially for switch-to-switch connections in a leaf-spine topology. The correct syntax for the link between port 1 on spine-01 and port 41 on gpu-leaf-01 is:

"spine-01":"swp01" -- "gpu-leaf-01":"swp41"

This syntax uses swp01 and swp41 to denote switch ports, consistent with Cumulus Linux conventions, and the double dash (--) to indicate the link, as required by the DOT file format.

Exact Extract from NVIDIA Documentation:

“You can create custom topologies in Air using a DOT file, which is the file type used with the open-source graph visualization software, Graphviz. DOT files define nodes, attributes, and connections for generating a topology for a network. The following is an example of a link definition in a DOT file:

"leaf01":"swp31" -- "spine01":"swp1"

This specifies a connection between port swp31 on leaf01 and port swp1 on spine01. Port names typically follow the switch port naming convention (e.g., swpX) for Cumulus Linux-based switches.”

—NVIDIA Air Custom Topology Guide

This extract confirms that option A is the correct answer, as it uses the proper DOT file syntax with swp01 and swp41 for port names and the double dash (--) for the link, aligning with NVIDIA AIR’s topology definition process for Spectrum-X simulations.

Analysis of Other Options:

B. "spine-01":"swp1" to "gpu-leaf-01":"swp41": This option uses the correct port naming convention (swp1 and swp41) but incorrectly uses the word to as the connector instead of the double dash (--). The DOT file format requires -- to define links, making this syntax invalid for NVIDIA AIR.

C. "spine-01":"eth1" to "gpu-leaf-01":"eth41": This option uses ethX port names, which are typically used for host interfaces (e.g., servers) rather than switch ports in Cumulus Linux or SONiC environments. Switch ports in Spectrum-X topologies are labeled swpX. Additionally, the use of to instead of -- is incorrect for DOT file syntax, making this option invalid.

D. "spine-01":"eth1" - "gpu-leaf-01":"eth41": This option uses a single dash (-) instead of the required double dash (--) and incorrectly uses ethX port names instead of swpX. The ethX naming is not standard for switch ports in Spectrum-X, and the single dash is not valid DOT file syntax, making this option incorrect.

Why "spine-01":"swp01" -- "gpu-leaf-01":"swp41" is the Correct Answer:

Option A correctly adheres to the DOT file syntax used in NVIDIA AIR for defining network links:

Node and Port Naming: The nodes spine-01 and gpu-leaf-01 are specified with their respective ports swp01 and swp41, following the swpX convention for switch ports in Cumulus Linux-based Spectrum-X switches.

Link Syntax: The double dash (--) is the standard connector in DOT files to indicate a link between two ports, as required by Graphviz and NVIDIA AIR.

Spectrum-X Context: In a Spectrum-X leaf-spine topology, connections between spine and leaf switches (e.g., Spectrum-4 switches) use switch ports labeled swpX, making swp01 and swp41 appropriate for this simulation.

This syntax ensures that the NVIDIA AIR simulation accurately models the physical connection between spine-01 port 1 and gpu-leaf-01 port 41, enabling validation of the Spectrum-X network topology. The DOT file can be uploaded to NVIDIA AIR to generate the topology, as described in the documentation.

In Cumulus Linux, microbursts are short-lived, high-volume traffic bursts that often go undetected by coarse-grained monitoring like SNMP.

The two tools specifically used for this purpose are:

What Just Happened (WJH)

"WJH provides real-time packet drop visibility and classifies drops by reason (e.g., congestion, ACLs, etc.), enabling microburst detection."

ASIC monitoring at millisecond granularity

"Deep telemetry is enabled via the switch ASIC, which provides sub-second counters that capture microburst patterns otherwise missed by SNMP."

Incorrect Options:

AandCprovide low-frequency sampling, insufficient for microbursts which last milliseconds.

Adaptive Routingin InfiniBand networks dynamically selects the optimal path for data packets based on current network conditions, such as congestion levels and link utilization. This approach ensures that traffic is evenly distributed across the network, preventing bottlenecks and maximizing overall throughput.​

By continuously monitoring the network and adjusting routes in real-time, Adaptive Routing enhances performance and reliability, making it the preferred choice for high-performance computing environments where consistent low latency and high bandwidth are critical.​

NVIDIA BlueField Data Processing Units (DPUs)are integral to securing AI infrastructures, especially in environments requiring stringent data privacy and security measures. BlueField DPUs offload and accelerate critical infrastructure tasks such as encryption, firewall enforcement, and intrusion detection, thereby isolating sensitive data paths from potential threats.​

In the context of AI workloads, BlueField DPUs enable secure and efficient data movement between GPUs and storage systems, ensuring that sensitive information, like financial data, is protected during both training and inference processes. Their integration into NVIDIA's reference architectures provides a hardware root of trust, essential for maintaining data integrity and compliance with security standards.​

The ibnetdiscover utility is used to perform InfiniBand subnet discovery and outputs a human-readable topology file. GUIDs, node types, and port numbers are displayed, as well as port LIDs and node descriptions. All nodes and links are displayed, providing a full topology. This utility can also be used to list the current connected nodes. The output is printed to the standard output unless a topology file is specified.​

InfiniBand is a high-performance, low-latency interconnect technology used in AI and HPC data centers, particularly for east-west traffic between compute nodes in large-scale fabrics. Ensuring seamless data flow requires tools to troubleshoot and monitor the network, including the ability to trace and discover network paths between nodes. The question asks for the specific tool used to trace and discover paths in an InfiniBand fabric, which is a key task in InfiniBand troubleshooting.

According to NVIDIA’s official InfiniBand documentation, the ibnetdiscover tool is designed to discover and map the topology of an InfiniBand fabric, including the paths between nodes. It scans the fabric, queries the subnet manager, and generates a topology map that details the connections between switches, Host Channel Adapters (HCAs), and other devices. This tool is essential for verifying connectivity, identifying routing paths, and troubleshooting issues like misconfigured routes or link failures in large-scale InfiniBand fabrics.

Exact Extract from NVIDIA Documentation:

“The ibnetdiscover tool is used to discover the InfiniBand fabric topology and generate a map of the network. It queries the subnet manager to retrieve information about all nodes, switches, and links in the fabric, providing a detailed view of the paths between nodes. This tool is critical for troubleshooting connectivity issues and ensuring proper routing in InfiniBand networks.”

—NVIDIA InfiniBand Networking Guide

This extract confirms that ibnetdiscover is the correct tool for discovering network paths in an InfiniBand east-west fabric. It provides a comprehensive view of the fabric’s topology, enabling administrators to trace paths between compute nodes and ensure seamless data flow.

Configuring NVUE to ignore certain underlying Linux files allows administrators to manage specific settings manually or through automation tools like Ansible withoutNVUE overwriting these configurations. This approach enables the persistent manipulation of settings using both NVUE and flat-file methods, providing flexibility in network management.

Before upgrading Cumulus Linux, it's essential to back up configuration files to a different server. The /etc directory is the primary location for all configuration data in Cumulus Linux. Specifically, the following files and directories should be backed up:​

/etc/frr/ - Routing application (responsible for BGP and OSPF)

/etc/hostname - Configuration file for the hostname of the switch

/etc/network/ - Network configuration files, most notably /etc/network/interfaces and /etc/network/interfaces.d/

/etc/cumulus/acl - Access control list configurations​

Cumulus Linux is a network operating system used on NVIDIA Spectrum switches, including those in the Spectrum-X platform, to provide a Linux-based environment forEthernet networking in AI and HPC data centers. When upgrading Cumulus Linux to a new version, it’s critical to migrate specific configuration files to preserve network settings and ensure continuity. The question asks for the two configuration file locations that should be migrated from the old installation during an upgrade.

According to NVIDIA’s official Cumulus Linux documentation, the key directories containing configuration files that should be migrated during an upgrade are /etc/cumulus/acl (for access control list configurations) and /etc/network (for network interface configurations). These directories store critical network settings that define the switch’s behavior, such as ACL rules and interface settings, which must be preserved to maintain network functionality after the upgrade.

Exact Extract from NVIDIA Documentation:

“When upgrading Cumulus Linux, you must back up and migrate specific configuration files to ensure continuity of network settings. The following directories should be included in the backup:

/etc/cumulus/acl: Contains access control list (ACL) configuration files that define packet filtering and security policies.

/etc/network: Contains network interface configuration files, such as interfaces and ifupdown2 settings, which define the network interfaces and their properties.Back up these directories before upgrading and restore them after the new version is installed to maintain consistent network behavior.”—NVIDIA Cumulus Linux Upgrade Guide

This extract confirms that options A and B are the correct answers, as /etc/cumulus/acl and /etc/network contain essential configuration files that must be migrated during a Cumulus Linux upgrade. These files ensure that ACL policies and network interface settings are preserved, which are critical for Spectrum-X configurations in AI networking environments.

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'."

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.

The ib_write_bw tool is part of the Perftest package and is specifically designed to measure the bandwidth of RDMA write operations between two InfiniBand endpoints. It provides accurate assessments of RDMA throughput, which is crucial for verifying the performance of InfiniBand networks in high-performance computing and AI training environments.​