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Fabric Link shutdown due to Autotuning failure

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TitleFabric Link shutdown due to Autotuning failure
Symptoms
Fabric Link shutdown due to Autotuning failure
Environment
  • MLXE-16-MR2
  • NI 6.0.00d
Cause
Individual fabric links between SFM modules and LP modules can suddenly be brought down by health monitoring and kept down by failing autotuning due to a number of factors. These can include but are not limited to:
  • External electromagnetic interference
  • Cosmic rays
  • Poor seating with no hardware failure
  • Hardware failure of the SFM module
  • Hardware failure of the chassis slot
Resolution
Identifying the cause requires troubleshooting and monitoring. Links between SFM and LP modules have extensive redundancy. If "show sfm-utilization all" shows no SFM module with high utilization, there is no harm in leaving a link permanently down. There is no need for action if a single link link goes down.

The following are optional troubleshooting steps that can be used if a user decides to pursue the issue anyways.

If the link stays up after executing "
power-off snm-link <SNM_#> <FE_#> <LINK_#>" and "power-on snm-link <SNM_#> <FE_#> <LINK_#>", then external electromagnetic or cosmic ray interference is most likely to blame.

If the same link goes down again, then reseating the SFM should be tried next. If the link stays up after reseating the SFM, then poor searting of the SFM was most likely the cause.

If the same link goes down again, then swapping the SFM should be tried next. If the link stays up afterwards, then a hardware issue in the SFM was most likely the cause.

If the same link goes down after swapping the SFM, then the LP module at the other end of the link, the SFM slot in the chassis, the LP seating, and the LP slot in the chassis become suspect. Identifying the cause further requires troubleshooting against each of those possibilities.

Again, links between SFM and LP modules have extensive redundancy. If "
show sfm-utilization all" shows no SFM module with high utilization, there is no harm in leaving a link permanently down. There is no need for action if a single link link goes down.
Additional notes

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