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The user receives the "%SYS-3-FAB_SYNCERR: [chars] detected" error message in Catalyst 6000/6500 series switches running CatOS


Core issue

This message indicates that a fabric channel error has been detected. [chars] is the type of channel error, the first [dec] is the channel number, and the second [dec] is the module number.


The system attempts to recover by re-synchronizing or resetting the module. If the system does not recover the module, replace the module.

The synchronization errors can be caused by a hardware issue or a badly seated card.  Issue the show fabric channel switchmode command to check whether the SYNC status is OK. If it is status is OK you can try re-seating the module with testing set to Complete only for testing. Confirm that the testing is error free and that there are no errors in the log.

Perform these steps:

  1. Issue the set test diaglevel {complete} command.   
  2. Reseat the module.   
  3. Issue the show test command, and check for any errors recorded.   
  4. Issue the show fabric channel counters command for any errors.   
  5. If found are errors, monitor to see if they increment.   
  6. Issue the show log command, and check for errors.   
  7. Issue the set test diaglevel command, and set it back to Minimal.   
  8. Verify that everything is error free.

For further assistance, open a case with Cisco Technical Support.