CSCwo18785: 'ERROR: The transceiver doesn't support this speed' with a third-party 200G DAC on Nexus 9332D-GX2B

Question

The poster, validating their product against Cisco Nexus 9000 switches (a Nexus C9332D-GX2B chassis), is blocked by bug CSCwo18785: configuring 200G on a QSFP-200G DAC fails with 'ERROR: The transceiver doesn't support this speed'. The cable is a Mellanox MCP1650-H002E26 200GbE DAC; connected back-to-back between two NVIDIA ConnectX-7 NICs in an Ubuntu 24.x server, without the Cisco switch, it auto-negotiates to 200 Gbps normally. The poster asked for the current status of the bug, which build contains the fix and when it would be publicly available.

Hardware: Cisco Nexus 9000 C9332D-GX2B, NVIDIA ConnectX-7 NIC (Ubuntu 24.x server)
Transceivers: Mellanox MCP1650-H002E26 200GbE QSFP56 DAC
Form factor: QSFP56, DAC

Symptoms / messages:

ERROR: The transceiver doesn't support this speed
cannot configure 200G on third-party QSFP-200G DAC
CSCwo18785
same DAC negotiates 200G between two ConnectX-7 NICs

portbear20 · Accepted Answer

This is a known bug, tracked as CSCwo18785. A fix is targeted for a release currently in testing - I've seen IOS-XE 17.9.3 cited, with public availability around late Q3 2025, though your platform is a Nexus running NX-OS, so that may not directly apply. I'd open a TAC case to get an interim engineering build or a workaround.

txnode67 · Answer

The bug is listed as Fixed, but its conditions say it's only seen with third-party 200G DAC cables - so Cisco may not prioritize shipping that fix.

wavesmith · Answer

A bug with status Fixed but no Known Fixed Releases means the developers have fixed it, but no customer release contains it yet. TAC can give you an ETA.

txnode67 · Answer

Try 'show interface transceiver support-list', 'show interface capability | include speed' and 'show idprom interface ' to check for speed, connector type, wavelength, FEC and transceiver-type mismatches. Cisco added these commands specifically to make such mismatches visible.

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