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Cisco Bug: CSCvi49093 - Reload reason after MTC double-bit ECC error is incorrect

Last Modified

Aug 14, 2018

Products (48)

  • Cisco Nexus 3000 Series Switches
  • Cisco Nexus 3548-X Switch
  • Cisco Nexus 9516 Switch
  • Cisco Nexus 3548 Switch
  • Cisco Nexus 31108TC-V Switch
  • Cisco Nexus 92304QC Switch
  • Cisco Nexus 9396TX Switch
  • Cisco Nexus 9396PX Switch
  • Cisco Nexus 3064 Switch
  • Cisco Nexus 3132Q-V Switch
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Known Affected Releases

6.0(2)A8(7) 6.0(2)A8(8) 7.0(3)I7(2)

Description (partial)

On the Nexus 3500, CSCuq98645 introduced a mechanism to detect and correct parity errors on the Monticello forwarding ASIC. This functionality exists in 6.0(2)A8(7), 7.0(3)I7(2) and later.

In the event of multiple double-bit ECC errors - which are not correctable - the only recovery method is to reload the switch. When this occurs, a message similar to the following will be printed to the syslogs:

<pre>2018 Jan 01 00:00:00.000 EDT: %USER-3-SYSTEM_MSG: MEMORY::DQ: Double ECC Error #23 detected on DQ BLOCK - Interrupt 2636(MTC_DQ_MBL_BV13_DERR_INTR_2), Front port 2, Total D-ECC in DQ block
 10, Total D-ECC Errors 23  - mtc_usd
2018 Jan 01 00:00:00.000 EDT: %USER-3-SYSTEM_MSG: MEMORY::DQ: Repeated Double ECC Errors were detected on DQ BLOCK. Total Double ECC errors in DQ BLOCK 10, Total memory Errors in DQ BLOCK 
25  - mtc_usd
2018 Jan 01 00:00:00.000 EDT: %USER-2-SYSTEM_MSG: Multiple memory errors detected - Reloading the box, check the onboard mtc_usd logs for details - mtc_usd</pre>

However, the last reload reason will be recorded as "Reset requested by CLI command reload":

<pre>`show system reset-reason`
----- reset reason for Supervisor-module 1 (from Supervisor in slot 1) ---
1) At 852428 usecs after Mon Jan 01 00:00:00 2018
    Reason: Reset Requested by CLI command reload    <--------------- !!
    Version: 6.0(2)A8(7)</pre>

This reload reason is confusing and causes needless concern, as a user seeing this would likely be inclined to look for evidence of a user typing the reload command.

This is seen on the Nexus 3500, on releases after the fix for CSCuq98645, when the system reloads due to an uncorrectable double-bit ECC error.
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