Mellanox 100G module power consumption limitations

The importance of power consumption is known and talked about. When talking about 100G used for up to 100m link (Intermediate Range) connections (EDGE SKU: 100G-QSFP28-100), transceivers can be ordered for both 3.5 W and 2 W or less power consumption.

The importance of selecting the correct power consumption is reiterated in a problem case of the Mellanox SN2100 switch and 100G QSFP28 modules. The Mellanox SN2100 switch will recognize the inserted 100G QSFP28 module with 4.5 W power consumption (Figure 1) and provide module and DDM information.

Figure 1

However, data traffic will not be present, and no packets will be sent or received (Figure 2) when inserted in most of the ports.

Figure 2

The problem has a simple fix that can be found by referring to Mellanox equipment (e.g., SN2000 Series) Product Documentation. Mellanox SN2100 switch documentation has information that ports have power usage restrictions. Ports 1, 2, 15, 16 have a power restriction of ≤4.5 W, and other ports have a power restriction of ≤3.5 W. As ≤4.5 W power consumption is expected for Long Range modules and not IR or SR modules.

Data connection is restored, and the problem is solved by replacing 100G QSFP28 3.5 W transceivers are replaced to 2 W or lower power consumption transceivers.

Mellanox switches are not the only ones to place power restrictions on ports or limit the number of transceivers in a unit (e.g., Aruba 8320 Switch Series limit on 10GBASE-T use at one time), however is a good reminder of the importance of power consumption parameters when selecting modules.