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Router reboot unexpectedly

Level 1
Level 1

Dear Expert,

Hope all is well.

One of cisco route 2921 reboot it unexpectedly and upon checking, we find out below result:

cisco router reload reason bus error at PC 0xB0D0B0D, address 0x0.

the firmware version: c2900-universalk9-mz.SPA.157-3.M8.bin


8 Replies 8


Hello @UsmanAkram1525 ,

can you provide the output of the following commands in order to try to investigate the reason of the crash:

  • show context
  • show region
  • show stacks
  • show tech

Please attach the outputs as files. Some of them are quite lengthy.

Regards, LG
*** Please Rate All Helpful Responses ***


the log is fairly generic. Here is a breakdown of what could be going on. If you are lucky, it is just a glitch, and it does not happen again. If it does happen again, it could be a software or a hardware issue. The 2921 is end of support, so the latest IOS you can download is the 15.7.3M8 release, which you are already running. Unfortunately, bus errors also can be hardware-related, in that case, your router is broken. How old is the router ?

The log message you provided indicates that the Cisco router experienced a bus error, leading to a system reload. Here is a breakdown of the components of the log message:

cisco router reload reason: This part of the message indicates that the router is reloading (restarting) due to a specific reason.

bus error: A bus error occurs when the router's central processing unit (CPU) encounters an invalid memory access on the system bus. This could be caused by a hardware or software issue.

at PC 0xB0D0B0D: The program counter (PC) is a register that holds the memory address of the instruction being executed. In this case, the PC value at the time of the bus error is 0xB0D0B0D.

address 0x0: The memory address 0x0 (zero) indicates that the error occurred at address zero, which is typically a null or uninitialized pointer.

The most common causes of bus errors include:

Hardware Issues: Faulty hardware components, such as RAM or other memory-related components, can cause bus errors.

Software Bugs: Bugs or software defects in the router's operating system (IOS) or running applications may lead to memory access violations.

Configuration Issues: Improper configuration settings may cause the router to access memory inappropriately.

To troubleshoot and resolve the issue, consider the following steps:

Upgrade the router's IOS to the latest stable release.
Check for any hardware issues, such as faulty RAM or other components.
Review the router's configuration for any misconfigurations.
Analyze crash dump information, if available, to identify the cause more precisely.
If you have access to Cisco support resources, consider reaching out to Cisco TAC (Technical Assistance Center) for further assistance in diagnosing and resolving the bus error issue.

Leo Laohoo
Hall of Fame
Hall of Fame

Post the complete output to the command "dir".

Level 1
Level 1

yes we did some config changes and after that we start facing this issue, we reverted back and will update here soon


we added the RAM module 2GB but error still remain but now we are moving to hardware upgrade to check

i need one suggestion which is creating the confusion. As per attached snapshot, kindly confirm is it available or use memory because due to multiple suggestion we get different answers so. please share your reviews on it. 





the memory seems to be available to the system, so it appears compatible. How old is the router ?

Dear @Georg Pauwen , 

I have to check for how old is this. but as i know in my presence it's more than a 2 years. 


Hello UsmanAkram1525,

In addition to our memeber suggestions...Please check the following link...and see helpfull or not....

Best regards
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