Nexus 93180YC-EX detects 25G SFP28 DAC and optics but the link never comes up
The poster, a new owner of a Cisco Nexus 93180YC-EX running NX-OS 7.0(3)I4(7), cannot bring up any 25G link. ipolex SFP28 DAC cables are recognized ('type is SFP-H25GB-CU1M', 'name is OEM', 'part number is SFP-H25G-CU1M', 'nominal bitrate is 25500 MBit/sec', 'DOM is not supported') but the port stays down even after 'service unsupported-transceiver'. Testing optics over a patch cable gave asymmetric results: a 25G SFP in the server and a 10G SFP in the switch links at 10G, but a 10G SFP in the server and a CISCO-FINISAR SFP-25G-SR-S (type SFP-H25GB-SR10M, part AZS85-S28-M1/GR, cisco part number 10-3227-01) in the switch never links, although 'show interface transceiver detail' shows healthy DOM values (Tx 1.19 dBm, Rx 0.56 dBm, Transmit Fault Count = 0). Eth1/30 and Eth1/31 are configured identically.
- Hardware: Cisco Nexus 93180YC-EX
- Transceivers: ipolex 25G SFP28 DAC (reported as SFP-H25GB-CU1M / SFP-H25G-CU1M), SFP-25G-SR-S (CISCO-FINISAR AZS85-S28-M1/GR), unspecified 10G SFP+
- Form factor: SFP28, DAC, SFP+
Symptoms / messages:
link down with 25G SFP28 DAC recognized as SFP-H25GB-CU1M
DOM is not supported
service unsupported-transceiver has no effect
10G SFP+ to SFP-25G-SR-S optical link stays down
link up at 10G only with the 10G module in the switch
Comments 2
A respondent pointed out that in the failing optical test the two ends run at different speeds (a 10G SFP+ on the server against a 25G SFP28 in the switch), which the poster confirmed; the same pair only works when the 10G module sits in the switch port.
Months later another user asked whether a resolution had ever been found; the no-link question for the 25G DAC was never answered in the thread.