System information

Book Title
The write core Command
A-500
A Core Dump Creation Example
The following example configures a router to use FTP to dump a core file to the FTP server at
172.17.92.2 when it crashes:
ip ftp username red
ip ftp password blue
exception protocol ftp
exception dump 172.17.92.2
Creating an Exception Memory Core Dump
During the debugging process, you can cause the router to create a core dump and reboot when
certain memory size parameters are violated. The exception memory commands define a minimum
contiguous block of memory in the free pool and a minimum size for the free memory pool. The
following is the syntax for the exception memory fragment and exception memory minimum
commands:
[no] exception memory fragment size
[no] exception memory minimum size
The value of size is in bytes and is checked every 60 seconds. If you enter a size that is greater than
the free memory and the exception dump command has been configured, a core dump and router
reload is generated after 60 seconds. If the exception dump command is not configured, the router
reloads without generating a core dump.
The following example configures the router to monitor the free memory. If it falls below
250000 bytes, it dumps the core and reloads:
exception dump 131.108.92.2
exception core-file memory.overrun
exception memory minimum 250000
The write core Command
You can test core dumps by using the write core privileged exec command. This command causes
the router to generate a core dump without reloading and is useful if the router is malfunctioning but
has not crashed.
Depending on your TFTP server, you might need to create an empty target file to which the router
can write the core.
show Commands
When a router fails with an unexpected reload and you report the problem to a technical support
representative, always include a copy of the output from the show stacks and show version exec
commands. Output from these commands provides the support representative with important
information about the state of your router when it failed.
The show stacks Command
The show stacks command displays data saved by the ROM monitor, which includes a failure type,
an operand address, and a failure program counter. This data is overwritten when the system is
reloaded, so check your configuration register settings and decide how you want to recover from
system crashes.