Using mlxlink to Inspect the Status of NVIDIA CX-6 NICs and Optical Modules

Table of Contents

This article provides a practical guide to using the mlxlink command to inspect the link and module status of NVIDIA’s ConnectX-6 (CX-6) network interface card (NIC). The same approach applies to other ConnectX series models. While mlxlink can also configure network parameters, configuration topics are beyond the scope of this article.

We begin by running the following command:

mlxlink -d mlx5_0 -m -c

This retrieves a comprehensive status report of the NIC and its optical module. Below is a breakdown of the output and explanation of each section.

Operational Info
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State                            : Active
Physical state                   : ETH_AN_FSM_ENABLE
Speed                            : 200G
Width                            : 4x
FEC                              : Standard RS-FEC (544,514)
Loopback Mode                    : No Loopback
Auto Negotiation                 : ON

Explanation:

State: Active
The NIC port is active and the link is operational.
Physical state: ETH_AN_FSM_ENABLE
Auto-negotiation at the physical layer is enabled. This status indicates the Physical Media Dependent (PMD) sublayer is in the Auto-Negotiation Finite State Machine mode.
Speed: 200G
Current link speed is 200 Gbps.
Width: 4x
The link consists of 4 channels, each at 50 Gbps, totaling 200 Gbps.
FEC: Standard RS-FEC (544,514)
Forward Error Correction is active, using Reed-Solomon encoding with a (544,514) scheme.
Loopback Mode: No Loopback
Loopback is disabled, meaning the port is communicating with an external device.
Auto Negotiation: ON
Auto-negotiation is enabled, allowing the NIC and its link partner to negotiate optimal speed and FEC settings.

Supported Info
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Enabled Link Speed (Ext.)        : 0x000017f2(200G,100G_2X,100G_4X,50G_1X,50G_2X,40G,25G,10G,1G)
Supported Cable Speed (Ext.)     : 0x000017d0(200G,100G_2X,100G_4X,50G_1X,50G_2X,25G,10G)

Explanation:

Enabled Link Speed (Ext.)
Lists supported line rates, including 200G (4×50G), 100G (2×50G or 4×25G), and down to 1G.
Supported Cable Speed (Ext.)
Shows the optical module’s rated cable speeds, such as 200G, 100G, 50G, and so on.

Troubleshooting Info
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Status Opcode                    : 0
Group  Opcode                    : N/A
Recommendation                   : No issue was observed.

Explanation:

Status Opcode: 0
A value of 0 means no error condition is currently detected.
Recommendation: No issue was observed
Indicates the system considers the link to be healthy.

Physical Counters and BER Info
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Time Since Last Clear [Min]      : 18285.8
Effective Physical Errors        : 0
Effective Physical BER           : 4E-15
Raw Physical BER                 : 1E-10
Raw Physical Errors Per Lane     : 2667124,2619081,190455,106349

Explanation:

Time Since Last Clear [Min]
Shows the duration (in minutes) since counters were last reset.
Effective Physical Errors: 0
Indicates no uncorrected physical layer errors occurred — a good sign of link stability.
Effective Physical BER: 4E-15
Bit Error Rate (BER) after error correction is extremely low, indicating near-ideal performance.
Raw Physical BER: 1E-10
The raw (pre-correction) BER is within acceptable range.
Raw Physical Errors Per Lane
Raw error counts per lane (e.g., over 2.6 million on lane 0), but all were corrected successfully, as reflected by the zero effective errors.

Module Info
#

Identifier                       : QSFP28
Compliance                       : Active Optical Cable with 50GAUI,100GAUI-2 or 200GAUI-4 C2M. Providing a worst BER of 10^(-6) or below
Cable Technology                 : 850 nm VCSEL
Cable Type                       : Active cable(active copper / optics)
OUI                              : Mellanox
Vendor Name                      : Mellanox
Vendor Part Number               : MFS1S00-H010E
Vendor Serial Number             : MT2007FT07419
Rev                              : A7
Attenuation(5g,7g,12g) [dB]      : N/A
FW Version                       : 37.50.322
Wavelength[nm]                   : 850
Transfer Distance [m]            : 10
Digital Diagnostic Monitoring    : Yes
Power Class                      : 5.0 W max
CDR RX                           : ON,ON,ON,ON
CDR TX                           : ON,ON,ON,ON
LOS Alarm                        : N/A
Temperature[C]                   : 62 [-10..80]
Voltage [mV]                     : 3270[3100..3500]
Bias Current[mA]                 : 7.396,7.392,7.4,7.4[5.492..8.5]
Rx Power Current[dBm]            : 0,0,0,0 [-14..6]
Tx Power Current [dBm]           : 0,0,0,0 [-12..6]

Explanation:

Identifier: QSFP28
Indicates the module type — in this case, QSFP28 form factor.
Compliance
The module complies with Active Optical Cable standards supporting 50G/100G/200G via 50GAUI-1, 100GAUI-2, or 200GAUI-4 interfaces.
Cable Technology: 850 nm VCSEL
Uses Vertical-Cavity Surface-Emitting Lasers operating at 850 nm — ideal for short-distance optical connections.
Cable Type: Active cable
Active Optical Cable (AOC) using either optical or copper technologies.
Vendor Info
Manufacturer is Mellanox (now part of NVIDIA), with part number MFS1S00-H010E and firmware revision A7.
Firmware Version: 37.50.322
Indicates the firmware running on the module.
Transfer Distance: 10m
The AOC supports up to 10 meters of reach.
Digital Diagnostic Monitoring: Yes
DDM is supported, allowing real-time monitoring of optical and electrical parameters.
Temperature: 62°C
Module temperature is within safe range (-10°C to 80°C), though close to the upper limit.
Voltage: 3270 mV
Power supply is stable at 3.27V (within the 3.1V–3.5V operating range).
Bias Current
Laser driver currents per channel are within normal operating range (approx. 7.4 mA vs. 5.5–8.5 mA expected).
Rx/Tx Power (dBm)
Receive and transmit optical power levels are currently 0 dBm across all channels, which is within expected operational limits.

Summary
#

The current link is operating normally at a speed of 200 Gbps using a 4×50G configuration. FEC and auto-negotiation are enabled, and no physical errors were observed after correction. The optical module is a 10-meter Mellanox AOC, operating within its specification with healthy diagnostics and no faults reported.