The ibtracert command is the InfiniBand equivalent of the TCP/IP traceroute utility. It is specifically designed to discover and display the path that packets take from a source port to a destination port within the InfiniBand fabric. By tracing the hops (switches) between the two specified compute nodes, a system administrator can verify the exact route, identify potential bottlenecks, and determine if the path is sub-optimal. This directly addresses the need to ensure the path is optimal and troubleshoot slow transfer rates between two specific endpoints.

B. ibstatus: This command queries the status of the local Host Channel Adapter (HCA) and does not provide any information about paths to other nodes in the fabric.

C. ibping: This tool verifies basic point-to-point connectivity and measures latency, but it does not reveal the network path taken between the two nodes.

D. ibnetdiscover: This command performs a full scan of the fabric to discover and display the entire network topology, which is not specific to a single path between two nodes.

1. NVIDIA Mellanox OFED for Linux User Manual (LTS v5.8-1.1.2.1), Chapter 10: Diagnostic Tools, Section 10.10, "ibtracert". The manual states, "ibtracert uses SMPs to trace the path from a source to a destination... It discovers the path and prints the hops from the source to the destination." This confirms its function for path tracing.

2. Ohio Supercomputer Center (OSC) Documentation, "Verifying InfiniBand Fabric". This university-affiliated supercomputing center guide explains the usage of InfiniBand diagnostic tools. It describes ibtracert as the command to "trace the path from the current node to another node in the fabric," validating its use for the scenario described.

3. Linux man pages (infiniband-diags), ibtracert(8). The official man page describes the utility's purpose: "trace the path from a source GID/LID to a destination GID/LID." This is the primary function required by the administrator in the question.