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Catalyst 2928 Switch Software Configuration Guide
OL-23389-01
Chapter 33 Troubleshooting
Using Debug Commands
Caution
Because debugging output is assigned high priority in the CPU process, it can render the system
unusable. For this reason, use
debug
commands only to troubleshoot specific problems or during
troubleshooting sessions with Cisco technical support staff. It is best to use
debug
commands during
periods of lower network traffic and fewer users. Debugging during these periods decreases the
likelihood that increased
debug
command processing overhead will affect system use.
Note
For complete syntax and usage information for specific
debug
commands, see the command reference
for this release.
Enabling Debugging on a Specific Feature
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.
