During an install today I came across a slight issue with Cisco UCS twinax cables - thought I would share it here with others for future reference;
Basically TG1/TG2 ports on both controllers were failing to come up (red on the Nimble GUI) when we looked on the Nexus we could see they were plugged in but not coming up (leading us to believe it was a physical cable problem). The issue was identified as being the cable type (despite both cables having the same part number SFP-H10GB-CU3M); The cables with 37-0961-01 on the SFP didn't work whereas 37-0961-02 worked just fine (these cables also had orange rubber management pulls as opposed to black)
Below is a photo of both for reference...
SFP-H10GB-CU3M (37-0961-01) - Which did not work....
SFP-H10GB-CU3M (37-0961-02) - Which did work !!
This is the answer my local Cisco Engineer provided:
The first version of passive cables were not MSA compliant.
Starting in v2, all CX1 passive cables are compliant to SFF-8472 v10.4.
So, that all said, make sure to use the cables that are version 2 or greater (37-0961-02)
Sorry for the confusion.