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Cisco Bug: CSCut07912 - Chassis shut down if one of the two FC does not see either tray

Last Modified

Jul 21, 2018

Products (18)

  • Cisco Carrier Routing System
  • Cisco CRS-1 Line Card Chassis (Dual)
  • Cisco CRS-X 8-Slot Single-Shelf System
  • Cisco CRS-1 16-Slot Line Card Chassis
  • Cisco CRS-X Multishelf System
  • Cisco CRS-3 Multishelf System
  • Cisco CRS-1 Line Card Chassis (Multi)
  • Cisco IOS XR Software
  • Cisco CRS-1 4-Slot Single-Shelf System
  • Cisco CRS-3 16-Slot Single-Shelf System
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Known Affected Releases


Description (partial)

Critical alarm.  Chassis will be shut down in 45 seconds.

Issue observed in a CRS-X running 5.3.1.

The chassis runs with 2 fan controllers (FC) and 2 fan trays.  If one of the FC does not see either one of the trays, it will raise an alarm and will make the remaining tray run at full speed (check with "#admin show environment fan") to avoid damage on the equipment.

There are situations where only one of the FC does not see either one of the trays.  In this case the speed will still be increased.  If the tray that remains recognized fails or it is removed, the following critical alarm will be raise:

RP/0/RP0/CPU0:ROUTER-NAME#RP/0/RP0/CPU0:Jan 21 10:49:27.217 MET: shelfmgrv2[391]: %PLATFORM-SHELFMGRV2-1-ALL_FANTRAYS_REMOVED : Critical Alarm: Alarm generated because all fan trays have been removed from the chassis. If at least one tray is not inserted within 45 seconds, the chassis will be shutdown

To avoid this behaviour DDTS CSCun91139 (Upper fan of rack 0 is running at higher speed) was implemented.  With this fix, both FCs need to raise the alarm for a failing tray before increasing the remaining tray speed.  However, this DDTS only fixes the speed of the fans.  If the trays  but the origin will still be present and the critical alarm will still be raise.

If one FC sees both trays, the above alarm should not be triggered.
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