The ibstat command is the standard utility from the infiniband-diags package designed specifically to query the status of InfiniBand Host Channel Adapters (HCAs). It provides detailed hardware-level information about the adapter and its ports. The output explicitly includes the port State (e.g., Active, Down, Initializing), Physical state (e.g., LinkUp), and the Link layer protocol (e.g., InfiniBand). This makes it the most direct and appropriate tool for verifying the specific low-level interface characteristics mentioned in the question. The -d flag can be used to specify the device, such as mlx50, which is a common identifier for NVIDIA ConnectX adapters.

A. rdma show devices: This command lists RDMA-capable devices recognized by the system but does not provide the detailed, real-time port state or link-layer information that ibstat does.

C. ifconfig ib0: This is a deprecated Linux command that displays Layer 3 (IP) network configuration. It lacks the ability to show InfiniBand-specific Layer 1 and Layer 2 details.

D. ip link show dev ib0: This command shows the network interface's state from the kernel's perspective (e.g., UP/DOWN). It does not report the detailed hardware-level InfiniBand port status, rate, or physical state.

1. NVIDIA MLNXOFED User Manual (Rev 23.10): Section 5.1.1, "ibstat," describes the command's purpose: "The ibstat utility displays basic information obtained from the local Channel Adapter (CA) ports." The sample output clearly shows fields for "State," "Physical state," and "Link layer," confirming its use for this exact task.

2. Linux man pages, ibstat(8): The official manual page for the command states its function is to "query the status of an InfiniBand Host Channel Adapter (HCA)." It details the information provided, including port states.

3. Princeton University Research Computing, "Troubleshooting InfiniBand": In the section "Checking the InfiniBand Link State," the guide instructs users to run ibstat as the primary command to check if the port state is "Active" and the physical state is "LinkUp," demonstrating its standard use in an academic/research environment. (Available via Princeton's PICSciE documentation).