Enabling Debugging On A Specific Feature; Enabling All-System Diagnostics - Cisco Catalyst 2950 Software Configuration Manual

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.

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 EtherChannel:
Switch# debug etherchannel
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:
•
•
To disable debugging of EtherChannel, enter this command in privileged EXEC mode:
Switch# no debug etherchannel
Alternately, in privileged EXEC mode, you can enter the undebug form of the command:
Switch# undebug etherchannel
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
Because debugging output takes priority over other network traffic, and because the debug all command
Caution
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 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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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 when 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.
Chapter 26 Troubleshooting
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