Spirent TestCenter: DX3-400GQ-T2 link does not come up using DAC cable with DUT


Doc ID    KNI15899
Version:    3.0
Status:    Published
Published date:    01/08/2020
Created Date:    01/08/2020
 

Symptoms


DX3-400GQ-T2 cannot link up using QSFP-DD DAC with DUT
 

Environment

 
  • DX3-400GQ-T2
  • Link is not coming up
  • QSFP-DD DAC
  • 2M DAC
  • 3M DAC
  • NRZ /  PAM4 modulation

Explanation/Resolution


Try the following options in order to make the link to comes up:
 
  1. Go to "Advance" tab under that particular port and change "De-emphasis an main tap swing" settings from Auto detect to Manual, and "Cable type and lenght" to 2m copper and hit APPLY, then shut and no shut DUT port.
 
  1. DX3-400GQ-T2 uses PM4 modulation and will NOT work if DUT ports are using NRZ modulation, so it is a requirement the DUT is using PAM4 as well, otherwise, the port will not come up.
    1. There is some certain DUT that may require a special configuration to run PM4 modulation,  check with your hw team in order to check on details about how to do it.
    2. e.g: If you want to run at 100G speed make sure the DUT has enabled 100GBBASE-CR2 - This is 2 lanes of 50G PAM4 per 100G port
 

Root Cause

 
  • Configuration

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