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A Catalyst 6500 Switch that runs CatOS crashes due to a "TLB (Load/Fetch) Exception" while the set vlan command is used


Core issue

A TLB (Load/Fetch) exception occurs when the CPU tries to access an invalid virtual address and appears similar to this sample:

*** TLB (Load/Fetch) Exception ***
Access address = 0x1478
PC = 0x1478, Cause = 0x8008, Status Reg = 0x30410002

This error typically repeats indefinitely until interrupted by a user-issued break sequence or by power-cycling the router (after which the error may resume).

This problem is identified in Cisco bug ID CSCef49268.

The trigger for this crash is related to the set vlan configuration command and port assignment.

This protocol timer crash is independent of the platform and is seen for all Supervisor 1, Supervisor 2, Supervisor 720 and Supervisor 32 modules.

The problem is seen with binary as well as text-config mode but is reproducible in the text-config mode.

The cause of the problem is due to a function that is called when a frame size changes on the switch and when the Virtual Local Area Network (VLAN) is set for a port.


The resolution to this issue is to upgrade the Catalyst OS (CatOS) on the switch to version 8.5(0.161) and later, which can be downloaded from the Catalyst 6500/6000 CatOS System Software Download page.

If any further issues occur, open a case with Cisco Technical Support.