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The "TLB (Store) Exception" error message appears in Catalyst 6500 Series Switches that run CatOS system software


Core issue

The error message can look similar to this:

TLB (Store) Exception ***
Access address = 0x10000403 PC = 0x8000fd60, Cause = 0xc, Status Reg = 0x30419003
monitor: command "boot" aborted due to exception

This error message can be observed during a CatOS to Cisco IOS  conversion. In Switch Processor (SP) ROM Monitor (ROMMON), when you try to boot from disk0 or slot0, this can result in a

boot loop or the router gets stuck in ROMMON mode.

This issue can be caused by a software image with a bad checksum or when the Flash card is not formatted.

In another scenario, a Catalyst 6500 switch that runs CatOS 7.x and 8.4 can unexpectedly reload due to a TLB Exception or memory corruption. Then, you receive the "Exception hdlr:Unaligned Addr" error message.

AdEL is an Address Error exception (load or instruction fetch), which is caused by misaligned memory access, for example, the address of the called function called that does not fall on a 32-bits boundary. The error is usually corrected by software. This issue is documented in Cisco bug ID CSCsb91548.


In order to resolve this issue, complete these steps:

  1. Erase or format the Flash card. Refer to the article How to format or erase files from Flash and NVRAM permanently for more information on how to format or erase files from Flash permanently.
  2. Re-download the Cisco IOS Software image or boot from another software image.

Refer to the article How to convert from hybrid mode to integrated Cisco IOS Software on a Catalyst 6000 series switch for information on CatOS to Cisco IOS conversion on a Catalyst 6000 Series Switch.

If the symptoms matches the bug, then the bug fix is provided in CatOS release 8.5(5.11) and later, which can be downloaded from the LAN Switching Software page.

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