NVIDIA Certified Professional: AI Networking Practice Questions: InfiniBand Troubleshooting Domain

Correct Answer: A

Explanation: Checking the subnet manager logs for errors is a crucial first step in diagnosing performance issues in an InfiniBand network. These logs can provide insights into network topology changes, device errors, and other issues. Rebooting devices, upgrading firmware, or replacing cables should be considered only after analyzing the logs.

Correct Answer: A

Explanation: Checking the subnet manager logs is the first step to diagnose issues when new switches are added, as it manages the routing and can reveal configuration or connectivity problems. 'ibping' and 'ibtracert' are useful for specific connectivity checks, and 'ibclearerrors' is not diagnostic.

Correct Answer: A

Explanation: 'ibclearerrors' is the command used to reset the error counters on an InfiniBand port. This can help in troubleshooting by providing a fresh start to monitor for new errors after changes are made. 'ibcheckerrors' and 'ibqueryerrors' are used to check and query errors, respectively, but do not reset counters. 'ibstat' provides port status information.

Correct Answer: B

Explanation: Checking the switch logs for errors is the first step in diagnosing issues after a firmware upgrade. Logs can provide insights into what went wrong. Rebooting or resetting the switch should only be considered after understanding the issue, and topology discovery is more useful for network configuration issues.

Correct Answer: C

Explanation: The correct answer is C. 'ibdiagnet' is a comprehensive diagnostic tool used in InfiniBand networks to identify and troubleshoot physical layer issues. It can detect faulty cables, connectors, and other hardware-related problems by scanning the network fabric and reporting anomalies. 'ibstat' provides status information about InfiniBand devices, 'ibping' checks connectivity between nodes, and 'perfquery' retrieves performance data, but none of these tools is as focused on physical layer diagnostics as 'ibdiagnet'.

Correct Answer: B

Explanation: 'ibnetdiscover' is used to gather detailed topology information of an InfiniBand fabric. It provides a comprehensive view of the fabric, including switches, links, and nodes, which is essential for troubleshooting complex connectivity issues. 'ibtracert' is used to trace the path between two nodes, 'ibping' tests connectivity, and 'ibclearerrors' clears error counters.

Correct Answer: B

Explanation: 'iblinkinfo' provides detailed information about the links in an InfiniBand fabric, including status and speed, which is crucial for diagnosing physical layer issues. 'ibping' checks connectivity, 'ibtracert' traces routes, and 'perfquery' queries performance counters.

Correct Answer: B

Explanation: 'ibdiagnet' is a diagnostic tool that provides a comprehensive report of the InfiniBand network, including error counters and configuration issues, which can help identify the source of packet loss. Rebooting switches or replacing cables should only be done after identifying specific issues. Increasing the MTU size may not address the underlying problem causing packet loss.

Correct Answer: C

Explanation: The 'perfquery' tool is used to query performance counters on InfiniBand devices, which can help identify issues such as high latency by analyzing traffic patterns and bottlenecks. 'ibstat' provides link information, 'ibping' checks connectivity, and 'ibclearerrors' clears error counters.

Correct Answer: A

Explanation: The 'ibping' tool is used to test connectivity and measure packet loss between InfiniBand nodes. It helps identify intermittent connectivity issues by sending packets and measuring the response. 'ibnetdiscover' is used for network topology discovery, 'ibstat' provides status information about InfiniBand devices, and 'ibtracert' traces the path packets take through the InfiniBand fabric.