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Spirent TestCentr: STC 5.36 - B2-800 appliance - FCS and FEC errors in b2b mode using Molex DAC in 400G mode

CRC error packets received by STC without any traffic runnings. This has been seen on B2-800 appliance at 400G mode, tried connecting few STC ports back to back with 1M Molex DAC cable and issue remains.


Some other details:
  • Tried with different cables and different DUT, the issue remains the same: 400G Spirent receiving CRC errors, with or without Link training enabled.
  • The same cable, DUT works fine at 800G speed.
  • Latest working version: 5.35/5.34
  • Issue follows the STC port. But sometimes STC port in which CRC error seen in random.
  • Issue happens Immediately. STC back to back setup, STC reports receiving CRC error even when there is no traffic.
  • Changing the Advanced options in the port configuration and issue persists
Spirent TestCenter:
  • STC 5.36
  • Device: B2-800-OSFP-4-T1S
  • DAC cable: Molex 1.0M 30AWG, P/N 2111661010

Bug. Corrected and validated in STC 5.37.

Root Cause


Product : Windows GUI