Mellanox 100G module power consumption limitations

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 correct power consumption is reiterated in a problem case of Mellanox SN2100 switch and 100G QSFP28 modules. 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

Problem has 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 has power restriction of ≤4.5 W and other ports has 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 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 restriction on ports or limit the number of transceivers in unit (e.g., Aruba 8320 Switch Series limit on 10GBASE-T use at one time), however is a good reminder for importance of power consumption parameter when selecting modules.