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Switching Mellanox NICs Between IB And Ethernet Modes

Time: 2025-10-13
        Mellanox VPI network cards support dual operating modes: InfiniBand (IB) and Ethernet, which can be switched flexibly based on actual usage requirements.
        This guide takes the Mellanox MCX556A-ECAT network card as an example to illustrate how to check and switch the operating mode of Mellanox NICs. All operations are performed on a CentOS 7.6 system.
        1. Run the command below to start the MST tool:
            mst start
        Then execute the following command to check MST device information:
            mst status
        In this example, the device name of the Mellanox MCX556A-ECAT adapter is mt4119_pciconf0.
        2. Run the query command, and replace <device> with the actual device name obtained above:
            mlxconfig -d /dev/mst/<device> query
        The query result shows that the Mellanox MCX556A-ECAT is a VPI adapter supporting EDR IB and 100GbE Ethernet. Check the LINK_TYPE_P1 and LINK_TYPE_P2 configuration items; both Port 1 and Port 2 work in IB mode by default.
        3. Use the following command to modify the NIC port mode:
            mlxconfig -d /dev/mst/<device> set LINK_TYPE_P1=1 LINK_TYPE_P2=1
        Parameter description:
            • 1 = IB mode
            • 2 = Ethernet mode
        After executing the command, enter y to confirm the modification. Reboot the server to make the new configuration take effect.
        • Set to IB mode:
        • Set to Ethernet mode:
        4. After mode switching, use QSFP28-100G-SR4 optical modules to verify link status, transceiver identification and DOM (Digital Optical Monitoring) information on the Mellanox MCX556A-ECAT NIC.
        Test results verify that both transceiver information and DOM data can be read normally in both modes. The link rate runs at EDR in IB mode and 100GbE in Ethernet mode.
Table 1 Optical Module Test Results in Two Working Modes
Mode
LINK Information
Identification and DOM Information
IB Mode
Ethernet Mode
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