Troubleshooting guide
A-1
ATM and Layer 3 Switch Router Troubleshooting Guide
OL-1969-01
APPENDIX
A
Debugging a Switch Router
This appendix provides an overview of the debug commands that might be helpful when troubleshooting
your switch router.
This appendix consists of the following sections:
• Using the Debug Interface, page A-2
• Enabling Message Logging, page A-6
Use debug commands to isolate problems, not to monitor normal network operation. Because the high
overhead of debug commands can disrupt switch router operation, use debug commands only when you
are looking for specific types of traffic or problems and have narrowed your problems to a likely subset
of causes.
Output formats vary with each debug command. Some generate a single line of output per packet, and
others generate multiple lines of output per packet. Some generate large amounts of output, and others
generate only occasional output. Some generate lines of text, and others generate information in field
format.
Follow these steps to minimize the negative impact of using debug commands:
Step 1 Use the no logging console global configuration command on your switch router. This command
disables all logging to the console terminal.
Step 2 Use Telnet to connect to a switch router port, and enter the enable EXEC command.
Step 3 Use the terminal monitor command to copy debug command output and system error messages to your
current terminal display.
As a result, you can view debug command output remotely, without being connected through the console
port.
Because the console port no longer has to generate character-by-character processor interrupts,
following this procedure minimizes the load created by using debug commands.
If you intend to keep the output of the debug command, spool the output to a file. The procedure for
setting up such a debug output file is described in the Cisco IOS Debug Command Reference publication.
This publication provides complete details regarding the function and output of debug commands, and
includes specific debug commands that are useful when troubleshooting specific problems.