Several ConnectX-3 cards never light up optical transceivers but work with DACs
Mellanox ConnectX-3 MCX314A-BCBT and MCX354A-FCB cards (firmware 2.42.5000, driver 5.50.14740.1) were detected in Windows 11 and Ubuntu 22.10 but no optical transceiver ever emitted light: Cisco QSFP-40G-SR-BD, Cisco SFP-10G-SR and Mellanox MFM1T02A-SR were tried on LC-LC OM3, aross three motherboards, several PCIe slots and both IB and Ethernet port modes, with firmware reflashed. Copper DACs worked normally on the same cards.
- Hardware: Mellanox ConnectX-3 MCX314A-BCBT, Mellanox ConnectX-3 MCX354A-FCB
- Transceivers: Cisco QSFP-40G-SR-BD, Cisco SFP-10G-SR, Mellanox MFM1T02A-SR
- Form factor: QSFP+, SFP+, DAC
Symptoms / messages:
no light from transceiver
no link light
DAC works, optics do not
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Comments 1
Suggestions covered confirming the latest firmware, avoiding Cisco-locked optics in favour of Mellanox or generic ones, verifying Ethernet vs InfiniBand mode and testing DACs; the DAC test confirmed the cards worked, but optics never activated, possibly due to a per-port power limit (about 1.5 W) below what the optics needed.