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Catalyst 3750-X and 3560-X Switch Software Configuration Guide
OL-25303-03
Chapter 1 Troubleshooting
Using Debug Commands
Note For complete syntax and usage information for specific debug commands, see the command reference
for this release.
Enabling Debugging on a Specific Feature
In a Catalyst 3750-X switch stack, when you enable debugging, it is enabled only on the stack master.
To enable debugging on a stack member, you must start a session from the stack master by using the
session switch-number privileged EXEC command. Then, enter the debug command at the
command-line prompt of the stack member.
All debug commands are entered in privileged EXEC mode, and most debug commands take no
arguments. For example, beginning in privileged EXEC mode, enter this command to enable the
debugging for Switched Port Analyzer (SPAN):
Switch# debug span-session
The switch continues to generate output until you enter the no form of the command.
If you enable a debug command and no output appears, consider these possibilities:
• The switch might not be properly configured to generate the type of traffic you want to monitor. Use
the show running-config command to check its configuration.
• Even if the switch is properly configured, it might not generate the type of traffic you want to
monitor during the particular period that debugging is enabled. Depending on the feature you are
debugging, you can use commands such as the TCP/IP ping command to generate network traffic.
To disable debugging of SPAN, enter this command in privileged EXEC mode:
Switch# no debug span-session
Alternately, in privileged EXEC mode, you can enter the undebug form of the command:
Switch# undebug span-session
To display the state of each debugging option, enter this command in privileged EXEC mode:
Switch# show debugging
Enabling All-System Diagnostics
Beginning in privileged EXEC mode, enter this command to enable all-system diagnostics:
Switch# debug all
Caution Because debugging output takes priority over other network traffic, and because the debug all privileged
EXEC command generates more output than any other debug command, it can severely diminish switch
performance or even render it unusable. In virtually all cases, it is best to use more specific debug
commands.
The no debug all privileged EXEC command disables all diagnostic output. Using the no debug all
command is a convenient way to ensure that you have not accidentally left any debug commands
enabled.
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