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A Cisco Catalyst 4500 switch with SUP IV running Cisco IOS System Software resets unexpectedly due to multibit ECC errors


Core issue

This issue is due to Cisco bug ID CSCed25996.

The Cisco Catalyst 4500 Supervisor WS-X4515 (SUP IV) sometimes resets unexpectedly. This problem is exhibited when one of the options of the CPU Memory Controller is enabled. A change in the ROMMON is required in order to resolve this reset problem. The ROMMON is the first application that boots up in a system reset and initializes the CPU.

These ROMMON versions exhibit the failure mode:

  • 12.1(11r)EW
  • 12.1(12r)EW
  • 12.1(19r)EW


This problem is resolved with the latest ROMMON version for the Cisco Catalyst 4500 platform. Though the resets are seen with Cisco IOS  Software, the resolution is in the ROMMON. The fix is integrated in ROMMON version 12.1(20r)EW1 and later. Though not mandatory, Cisco recommends that the ROMMON be upgraded to the latest release available on CCO Downloads.

The issue can also be resolved if the CPU Memory Controller option is disabled.