Core Dumps

When contacting CCO, one of the troubleshooting methods they may ask you to perform is a core dump. If a router crashes, it may be useful to obtain a copy of the memory to see whether it indicates a cause for the crash. A core dump contains a picture of the information that is currently in the system memory. If your system memory (RAM) is very large, the core dump file also will be very large.

Using core dump commands most likely will disrupt a production network while they are being performed. Use caution when using the commands. You should make sure that a slow down of the routers processing power will not effect the network's users.

You use the exception command to create a core dump. This command is used only after the router has crashed. Using the exception command enables you to configure a router to execute a core dump if a router has crashed. Before you use the exception command, you must know the IP address of a server, such as a TFTP, FTP, or RCP server. The following is an example of configuring an exception command to a TFTP server:

 Support# Support#  config t  Enter configuration commands, one per line. End with    CNTL/Z. Support(config)#  exception dump 207.212.78.110  Support(config)#  ^C  Support#

A TFTP server doesn't require any additional commands, whereas sending a core dump to an FTP or an RCP server requires a few additional commands to allow the transfer. The following is an example of configuring a core dump to an FTP server:

 Support# Support#  config t  Enter configuration commands, one per line. End with    CNTL/Z. Support(config)#  exception protocol ftp  Support(config)#  ip ftp username support  Support(config)#  ip ftp password ccnp  Support(config)#  ip ftp source-interface serial 1  Support(config)#  exception dump 207.212.78.110  Support(config)#  exit  Support#

When a router is still on a network, you may also create a core dump from the command line. The following is an example of configuring a write core command:

 Support# Support#  write core  Remote host?  207.212.78.110  Name of core file to wite [Router_A-core]? Write file Router_A-core on host 207.212.78.110? [confirm] Writing Router_A-core !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! [OK] Support#

After you execute this command, the Cisco TAC personnel will be able to look at the dump and try to determine the problem the router is having. The core dump file will not be useful without the Cisco TAC personnel to interpret the source code.

When you retrieve a core dump from your router, the core dump will be in the form of a binary file. The binary file length will depend on the size of the memory in your router. After you retrieve the core dump, you must transfer the binary file to a server such as Trivial File Transfer Protocol (TFTP), File Transfer Protocol (FTP), or Remote Copy Protocol (RCP) server. At this point, you can send the file to Cisco personnel where it is then interpreted. Technical support representatives have access to the source code and memory maps to help identify the problem of the router before it crashed.

Cisco has a new Web site at http://c2.cisco.com. This Web site allows the Cisco technical support person helping you to use a chat feature or telnet from your local PC in to the router or switch you are working on. This feature allows you to view in real time or save a log of what the support representative does to help you.

After creating a core dump file, you may also want to include a few other files for the Cisco TAC. In the Privilege Exec Mode, the show stacks command will display data saved by the ROM monitor, which includes a failure type, an operand address, and a failure counter. Another good command is the show version command. This command shows the IOS version number, which enables the Cisco TAC personnel to make a more informed decision about how to handle the problem, since some versions of the IOS have various bugs that may contribute to the problem you are experiencing. If you're troubleshooting Ethernet, you should also include the show interfaces command as well.

By collecting all this information and forwarding this to the Cisco TAC, you can help in resolving your technical support issue quickly.