Cisco WS-C2960-24TC-S Software Guide - Page 637
Enabling All-System Diagnostics, Redirecting Debug and Error Message Output
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Chapter 32 Troubleshooting Using Debug Commands 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. Redirecting Debug and Error Message Output By default, the network server sends the output from debug commands and system error messages to the console. If you use this default, you can use a virtual terminal connection to monitor debug output instead of connecting to the console port. Possible destinations include the console, virtual terminals, internal buffer, and UNIX hosts running a syslog server. The syslog format is compatible with 4.3 Berkeley Standard Distribution (BSD) UNIX and its derivatives. Note Be aware that the debugging destination you use affects system overhead. Logging messages to the console produces very high overhead, whereas logging messages to a virtual terminal produces less overhead. Logging messages to a syslog server produces even less, and logging to an internal buffer produces the least overhead of any method. For more information about system message logging, see Chapter 25, "Configuring System Message Logging." OL-8603-04 Catalyst 2960 Switch Software Configuration Guide 32-19
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