Creating Core Dumps - Internetworking Troubleshooting - page 799

Advanced Setup
The configuration commands in this section may be used in addition to those described in the “Basic
Setup” section.
Exception Memory
During the debugging process, you can cause the router to create a core dump and reboot when certain
memory size parameters are violated. The following exception memory commands are used to trigger
a core dump:
exception memory minimum size
The previous code is used to define the minimum free memory pool size.
exception memory fragment size
The previous code is used to define the minimum size of contiguous block of memory in the free pool.
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 if 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.
Debug Sanity
In some cases, the technical support representative will request that debug sanity be enabled when
setting up the core dump. This is a hidden command in most IOS releases, but it sometimes is necessary
to debug memory corruption. With debug sanity , every buffer that is used in the system is
sanity-checked when it is allocated and when it is freed.
The debug sanity command must be issued in privileged exec mode (enable mode) and involves some
CPU utilization. However, it will not significantly affect the router's functionality.
Not all types of crash require debug sanity to be enabled. Use this command only when your technical
support representative requires it.
To disable debug sanity , use the privileged exec command undebug sanity .
Testing the Core Dump Setup
When the router is configured for core dump, it may be useful to test whether the setup works.
The IOS provides a special command to test or trigger a core dump:
write core
Use this command in privileged exec mode (enable mode). This command will cause a crash, and the
content of the memory will be dumped accordingly. If it no core dump is generated, the whole setup and
config must be reviewed.