When the error handler of the Layer 2 forwarding table Error-Correcting Code (ECC) does not work properly, Cisco Catalyst 6500 switches crash with Traceback errors. This problem occurs in Cisco IOS Software Release 12.2SX. Cisco bug ID CSCef35707 identifies this problem.
This is the sequence of steps to the problem:
A forwarding Application Specific Integrated Circuit (ASIC) at Layer 2 maintains the Layer 2 MAC table. When this forwarding ASIC detects ECC errors, the software acts upon it to correct the error. Several entries with ECC errors cause the system to run in a crippled condition.
This system condition affects the Distributed Forwarding Card (DFC) module on 67xx cards. If another forwarding ASIC reports a forwarding table ECC error, the software incorrectly assumes that the error belongs to the first forwarding ASIC. This way, continuous errors are reported and finally the board crashes.
In some scenarios, the crash is observed in the line card WS-X6704-10GE installed Sup720 based system.
Try this for the workaround:
Issue the clear mac-address-table dynamic command in order to clear the dynamic address entries from the Layer 2 MAC address table.
This problem is fixed in Cisco IOS Software Releases 12.2(18)SXD3, Cisco IOS Software Releases 12.2(17d)SXB6, and Cisco IOS Software Releases 12.2(18)SXE, which are available at Cisco Downloads.