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Router reloads due to a bus error

Core Issue

The system encounters a bus error when the processor tries to access a memory location that either does not exist (a software error) or does not respond properly (a hardware problem). A bus error can be identified by looking at the output of the show version command. This is provided by the router, if not power cycled or manually reloaded.


To find out whether you have a Cisco IOS  Software problem or a router hardware problem, you need to determine the memory location that the router tried to access when the bus error occurred. 

You can find the memory location by looking at the address in the output of the show version command, as shown in this example:


Router#show version
Router uptime is 2 days, 21 hours, 30 minutes
System restarted by bus error at PC 0x30EE546, address 0xBB4C4
System image file is "flash:igs-j-l.111-24.bin", booted through Flash


With the address accessed by the router when the bus error occurred, determine the memory location that the address corresponds to by issuing the show region command. 

If the address reported by the bus error does not fall within the ranges displayed in the output of the show region command, the router was trying to access an address that is not valid. This indicates that it is a Cisco IOS Software problem. 

To identify the Cisco IOS Software bug that is causing the bus error, refer to  the Output Interpreter Tool. This decodes the output of the show stacks command.   

If the address falls within one of the ranges in the show region command output, it means that the router was accessing a valid memory address, but the hardware corresponding to that address is not responding properly.

This is the sample output:

Router#show region
Region Manager: 
     Start         End     Size(b)  Class  Media  Name
0x00000000  0x007FFFFF     8388608  Local  R/W    main 

0x00001000  0x0001922F       98864  IData  R/W    main:data 

0x00019230  0x000666B3      316548  IBss   R/W    main:bss 

0x000666B4  0x007FEFFF     7965004  Local  R/W    main:heap 

0x007FF000  0x007FFFFF        4096  Local  R/W    main:flhlog 

0x00800000  0x009FFFFF     2097152  Iomem  R/W    iomem 

0x03000000  0x037FFFFF     8388608  Flash  R/O    flash 

0x0304033C  0x037A7D3F     7764484  IText  R/O    flash:text

This output indicates a hardware problem. The main corresponds to main memory or DRAM. The iomem corresponds to I/O memory, which means different parts for different platforms (such as DRAM for the Cisco 2500 series router and Shared RAM (SRAM) for the Cisco 4000 series router).

For additional instructions on interpreting the show region command, refer to the Troubleshooting Bus Error Crashes section of Troubleshooting Bus Error Crashes.   

When hardware replacement is indicated, choose from one of these options:


  • If you have a hardware support contract directly with Cisco for this part, use the Service Order Submit Tool to request a replacement part directly.
  • For warranty service, contact the Cisco Technical Assistance Center  (TAC) directly at 1-800-553-2447, or online using the TAC Service Request Tool.
  • If your product is not covered by contract or warranty, contact your Cisco partner or reseller to request a replacement part for the hardware component that is causing the issue.