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If the ATM switch fails, it is sometimes useful to obtain a full copy of the memory image, called a core dump, to identify the cause. Core dumps are generally only useful to your technical support representative.
 | Caution Use the commands discussed in this appendix only under the direction of a technical support representative. Creating a core dump while the switch is functioning in a network can disrupt network operation. The resulting binary file, which is very large, must be transferred to a Trivial File Transfer Protocol (TFTP), File Transfer Protocol (FTP), or remote copy (rcp) server and subsequently interpreted by technical personnel who have access to source code and detailed memory maps. |
Use the exception class of configuration commands only after consulting with a technical support representative. These commands are useful for debugging purposes, but they can result in unexpected behavior.
To obtain a core dump when a switch fails, use the exception dump ip-address switch configuration command (where ip-address is the address of your TFTP server).
If you include this command in your configuration, the switch attempts a core dump when it crashes. The core dump is written to a file named hostname-core on your server, where hostname is the name of the switch. You can change the name of the core file by configuring the exception core-file filename command.
The default protocol used for transferring the core dump is TFTP. However, TFTP transfers only 16 MB of the core dump file. If the switch memory is over 16 MB, only the first 16 MB will be transferred. In order to transfer the whole core dump, configure the switch to use rcp or FTP for core dumps with the exception protocol command.
The following example configures a switch to use rcp to dump the core file when it crashes:
ip rcmd remote-username red exception protocol rcp exception dump 172.17.92.2
The following example configures a switch to use FTP to dump the core file when it crashes:
ip ftp username red ip ftp password blue exception protocol ftp exception dump 172.17.92.2
This procedure can fail for certain types of system crashes. However, if successful, the core dump file will be the size of the memory available on the processor.
During the debugging process, you can cause the switch 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.
[no] exception memory fragment sizeThe 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, the switch creates a core dump and reloads the Cisco IOS software after 60 seconds. If the exception dump command is not configured, the switch reloads without generating a core dump.
The following example configures the switch to monitor the free memory. If the free memory falls below 250,000 bytes, the switch will dump the core and reload.
exception dump 131.108.92.2 exception core-file memory.overrun exception memory minimum 250000
You can create test core dumps by using the write core privileged EXEC command. If you use this command, the switch generates a core dump without reloading, which is useful if the switch is malfunctioning but has not crashed.
| Caution Use the write core command only under the direction of a technical support representative. Creating a core dump while the switch is functioning in a network can disrupt network operation. The resulting binary file, which is very large, must be transferred to a TFTP, FTP, or rcp server and subsequently interpreted by technical personnel who have access to source code and detailed memory maps. |
Depending on your TFTP server, you might need to create an empty target file to which the switch can write the core.
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