Log messages cannot be seen while consoled into a switch due to logging configuration settings

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Wed, 07/22/2009 - 19:37
Jun 18th, 2009
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Core issue

If log messages are not seen during a console session, it could be due to console logging being disabled or the logging level being set too low to display certain log messages.


Resolution

To resolve this issue, perform these steps:


  1. To check logging settings on a Cisco IOS  Software based device, issue the show log command.

    This is sample output from this command:

    Switch#show log
    Syslog logging: enabled (0 messages dropped, 0 flushes, 0 overruns)
        Console logging: level debugging, 22 messages logged
        Monitor logging: level debugging, 0 messages logged
        Buffer logging: level debugging, 22 messages logged
        File logging: disabled
        Trap logging: level informational, 26 message lines logged

    Log Buffer (4096 bytes):

    In this example, the console logging is set to the highest level (debugging), so all log messages should show up in a console session.

       
  2. To change the logging level on a Cisco IOS Software based device, issue the logging console global configuration command.

    For example, to set the console logging level to informational, issue the logging console informational command.

    After this command is issued, only informational level messages show up on the console.


  3. To disable console logging completely, issue the no logging console global configuration command.  


  4. To check logging settings on a Catalyst OS (CatOS) switch, issue the show logging command.

    Issuing the show logging command on a CatOS switch will not give any information about logging levels, but rather a log history.

    This example output is from the show logging command from a CatOS switch:

    Console> (enable) show logging

    Logging buffer size:          500
            timestamp option:     enabled
    Logging history size:         1
    Logging console:              enabled
    Logging telnet:               disabled
    Logging server:               disabled
            server facility:      LOCAL7
            server severity:      warnings(4)


    Facility            Default Severity         Current Session Severity
    -------------       -----------------------  ------------------------
    cdp                 4                        4
    cops                2                        2
    dtp                 5                        5
    earl                2                        2
    filesys             2                        2
    gvrp                2                        2
    ip                  2                        2
    kernel              2                        2
    mcast               2                        2
    mgmt                5                        5
    mls                 5                        5
    pagp                5                        5
    protfilt            2                        2
    pruning             2                        2
    qos                 3                        3
    radius              2                        2
    security            2                        2
    snmp                2                        2
    spantree            2                        2
    sys                 5                        5
    tac                 2                        2
    tcp                 2                        2
    telnet              2                        2
    tftp                2                        2
    udld                4                        4
    vtp                 2                        2


    0(emergencies)        1(alerts)             2(critical)
    3(errors)             4(warnings)           5(notifications)
    6(information)        7(debugging)


       
  5. In this example, console logging is enabled and all logging severities are set to their default levels.

    To disable console logging, issue the set logging console command.


       
  6. To change the level of logging for a particular facility, issue the set logging level facility severity [default] command.

    For example, to set the logging level for spanning-tree to debugging, issue the set logging level spantree 7 command.

    This sets the level to debugging only for the current session. If the optional default is added to the command, the level remains at debugging in subsequent sessions.


For more information on the configuration of logging, refer to these documents:

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