Consolidated Platform Configuration Guide, Cisco IOS XE 3.3SE (Catalyst 3850 Switches)
Configuring System Message Logs
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Configuring System Message Logs

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release.

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Information About Configuring System Message Logs

System Messsage Logging

By default, a switch sends the output from system messages and debug privileged EXEC commands to a logging process. Stack members can trigger system messages. A stack member that generates a system message appends its hostname in the form of hostname-n, where n is a switch range from 1 to 4, and redirects the output to the logging process on the active switch. Though the active switch is a stack member, it does not append its hostname to system messages. The logging process controls the distribution of logging messages to various destinations, such as the logging buffer, terminal lines, or a UNIX syslog server, depending on your configuration. The process also sends messages to the console.

When the logging process is disabled, messages are sent only to the console. The messages are sent as they are generated, so message and debug output are interspersed with prompts or output from other commands. Messages appear on the active consoles after the process that generated them has finished.

You can set the severity level of the messages to control the type of messages displayed on the consoles and each of the destinations. You can time-stamp log messages or set the syslog source address to enhance real-time debugging and management. For information on possible messages, see the system message guide for this release.

You can access logged system messages by using the switch command-line interface (CLI) or by saving them to a properly configured syslog server. The switch software saves syslog messages in an internal buffer on a standalone switch, and in the case of a switch stack, on the active switch. If a standalone switch or the stack master fails, the log is lost unless you had saved it to flash memory.

You can remotely monitor system messages by viewing the logs on a syslog server or by accessing the switch through Telnet, through the console port, or through the Ethernet management port. In a switch stack, all stack member consoles provide the same console output.


Note


The syslog format is compatible with 4.3 BSD UNIX.


System Log Message Format

System log messages can contain up to 80 characters and a percent sign (%), which follows the optional sequence number or time-stamp information, if configured. Depending on the switch, messages appear in one of these formats:

  • seq no:timestamp: %facility-severity-MNEMONIC:description (hostname-n)
  • seq no:timestamp: %facility-severity-MNEMONIC:description
The part of the message preceding the percent sign depends on the setting of these global configuration commands:
  • service sequence-numbers
  • service timestamps log datetime
  • service timestamps log datetime [localtime] [msec] [show-timezone]
  • service timestamps log uptime
Table 1 System Log Message Elements

Element

Description

seq no:

Stamps log messages with a sequence number only if the service sequence-numbers global configuration command is configured.

timestamp formats:

mm/dd h h:mm:ss

or

hh:mm:ss (short uptime)

or

d h (long uptime)

Date and time of the message or event. This information appears only if the service timestamps log [datetime | log] global configuration command is configured.

facility

The facility to which the message refers (for example, SNMP, SYS, and so forth).

severity

Single-digit code from 0 to 7 that is the severity of the message.

MNEMONIC

Text string that uniquely describes the message.

description

Text string containing detailed information about the event being reported.

hostname-n

Hostname of a stack member and its switch number in the stack. Though the active switch is a stack member, it does not append its hostname to system messages.

Default System Message Logging Settings

Table 2 Default System Message Logging Settings

Feature

Default Setting

System message logging to the console

Enabled.

Console severity

Debugging.

Logging file configuration

No filename specified.

Logging buffer size

4096 bytes.

Logging history size

1 message.

Time stamps

Disabled.

Synchronous logging

Disabled.

Logging server

Disabled.

Syslog server IP address

None configured.

Server facility

Local7

Server severity

Informational.

Syslog Message Limits

If you enabled syslog message traps to be sent to an SNMP network management station by using the snmp-server enable trap global configuration command, you can change the level of messages sent and stored in the switch history table. You also can change the number of messages that are stored in the history table.

Messages are stored in the history table because SNMP traps are not guaranteed to reach their destination. By default, one message of the level warning and numerically lower levels are stored in the history table even if syslog traps are not enabled.

When the history table is full (it contains the maximum number of message entries specified with the logging history size global configuration command), the oldest message entry is deleted from the table to allow the new message entry to be stored.

The history table lists the level keywords and severity level. For SNMP usage, the severity level values increase by 1. For example, emergencies equal 1, not 0, and critical equals 3, not 2.

How to Configure System Message Logs

Setting the Message Display Destination Device

If message logging is enabled, you can send messages to specific locations in addition to the console.

This task is optional.

SUMMARY STEPS

    1.    configure terminal

    2.    logging buffered [size]

    3.    logging host

    4.    logging file flash: filename [max-file-size [min-file-size]] [severity-level-number | type]

    5.    end

    6.    terminal monitor


DETAILED STEPS
      Command or Action Purpose
    Step 1 configure terminal


    Example:
    Switch# configure terminal
    
    
     

    Enters global configuration mode.

     
    Step 2 logging buffered [size]


    Example:
    Switch(config)# logging buffered 8192
    
    
     

    Logs messages to an internal buffer on the switch or on a standalone switch or, in the case of a switch stack, on the active switch. The range is 4096 to 2147483647 bytes. The default buffer size is 4096 bytes.

    If a standalone switch or the active switch fails, the log file is lost unless you previously saved it to flash memory. See Step 4.

    Note   

    Do not make the buffer size too large because the switch could run out of memory for other tasks. Use the show memory privileged EXEC command to view the free processor memory on the switch. However, this value is the maximum available, and the buffer size should not be set to this amount.

     
    Step 3 logging host


    Example:
    Switch(config)# logging 125.1.1.100
    
    
     

    Logs messages to a UNIX syslog server host.

    host specifies the name or IP address of the host to be used as the syslog server.

    To build a list of syslog servers that receive logging messages, enter this command more than once.

     
    Step 4 logging file flash: filename [max-file-size [min-file-size]] [severity-level-number | type]


    Example:
    Switch(config)# logging file flash:log_msg.txt 40960 4096 3
    
    
     

    Stores log messages in a file in flash memory on a standalone switch or, in the case of a switch stack, on the active switch.

    • filenameEnters the log message filename.
    • (Optional) max-file-size Specifies the maximum logging file size. The range is 4096 to 2147483647. The default is 4096 bytes.
    • (Optional) min-file-sizeSpecifies the minimum logging file size. The range is 1024 to 2147483647. The default is 2048 bytes.
    • (Optional) severity-level-number | typeSpecifies either the logging severity level or the logging type. The severity range is 0 to 7.
     
    Step 5 end


    Example:
    Switch(config)# end
    
    
     

    Returns to privileged EXEC mode.

     
    Step 6 terminal monitor


    Example:
    Switch# terminal monitor
    
    
     

    Logs messages to a nonconsole terminal during the current session.

    Terminal parameter-setting commands are set locally and do not remain in effect after the session has ended. You must perform this step for each session to see the debugging messages.

     

    Synchronizing Log Messages

    You can synchronize unsolicited messages and debug privileged EXEC command output with solicited device output and prompts for a specific console port line or virtual terminal line. You can identify the types of messages to be output asynchronously based on the level of severity. You can also configure the maximum number of buffers for storing asynchronous messages for the terminal after which messages are dropped.

    When synchronous logging of unsolicited messages and debug command output is enabled, unsolicited device output appears on the console or printed after solicited device output appears or is printed. Unsolicited messages and debug command output appears on the console after the prompt for user input is returned. Therefore, unsolicited messages and debug command output are not interspersed with solicited device output and prompts. After the unsolicited messages appear, the console again displays the user prompt.

    This task is optional.

    SUMMARY STEPS

      1.    configure terminal

      2.    line [console | vty] line-number [ending-line-number]

      3.    logging synchronous [level [severity-level | all] | limit number-of-buffers]

      4.    end


    DETAILED STEPS
        Command or Action Purpose
      Step 1 configure terminal


      Example:
      Switch# configure terminal
      
      
       

      Enters global configuration mode.

       
      Step 2 line [console | vty] line-number [ending-line-number]


      Example:
      Switch(config)# line console
      
      
       

      Specifies the line to be configured for synchronous logging of messages.

      • console Specifies configurations that occur through the switch console port or the Ethernet management port.
      • line vty line-numberSpecifies which vty lines are to have synchronous logging enabled. You use a vty connection for configurations that occur through a Telnet session. The range of line numbers is from 0 to 15.

      You can change the setting of all 16 vty lines at once by entering:

      line vty 0 15

      You can also change the setting of the single vty line being used for your current connection. For example, to change the setting for vty line 2, enter:

      line vty 2

      When you enter this command, the mode changes to line configuration.

       
      Step 3 logging synchronous [level [severity-level | all] | limit number-of-buffers]


      Example:
      Switch(config)# logging synchronous level 3 limit 1000
      
      
       

      Enables synchronous logging of messages.

      • (Optional) level severity-levelSpecifies the message severity level. Messages with a severity level equal to or higher than this value are printed asynchronously. Low numbers mean greater severity and high numbers mean lesser severity. The default is 2.
      • (Optional) level allSpecifies that all messages are printed asynchronously regardless of the severity level.
      • (Optional) limit number-of-buffersSpecifies the number of buffers to be queued for the terminal after which new messages are dropped. The range is 0 to 2147483647. The default is 20.
       
      Step 4 end


      Example:
      Switch(config)# end
      
      
       

      Returns to privileged EXEC mode.

       

      Disabling Message Logging

      Message logging is enabled by default. It must be enabled to send messages to any destination other than the console. When enabled, log messages are sent to a logging process, which logs messages to designated locations asynchronously to the processes that generated the messages.

      Disabling the logging process can slow down the switch because a process must wait until the messages are written to the console before continuing. When the logging process is disabled, messages appear on the console as soon as they are produced, often appearing in the middle of command output.

      The logging synchronous global configuration command also affects the display of messages to the console. When this command is enabled, messages appear only after you press Return.

      To reenable message logging after it has been disabled, use the logging on global configuration command.

      This task is optional.

      SUMMARY STEPS

        1.    configure terminal

        2.    no logging console

        3.    end


      DETAILED STEPS
          Command or Action Purpose
        Step 1 configure terminal


        Example:
        Switch# configure terminal
        
        
         

        Enters global configuration mode.

         
        Step 2 no logging console


        Example:
        Switch(config)# no logging console
        
        
         

        Disables message logging.

         
        Step 3 end


        Example:
        Switch(config)# end
        
        
         

        Returns to privileged EXEC mode.

         

        Enabling and Disabling Time Stamps on Log Messages

        By default, log messages are not time-stamped.

        This task is optional.

        SUMMARY STEPS

          1.    configure terminal

          2.    Use one of these commands:

          • service timestamps log uptime
          • service timestamps log datetime[msec | localtime | show-timezone]

          3.    end


        DETAILED STEPS
            Command or Action Purpose
          Step 1 configure terminal


          Example:
          Switch# configure terminal
          
          
           

          Enters global configuration mode.

           
          Step 2 Use one of these commands:
          • service timestamps log uptime
          • service timestamps log datetime[msec | localtime | show-timezone]


          Example:
          Switch(config)# service timestamps log uptime
          
          

          or

          Switch(config)# service timestamps log datetime
          
          
           

          Enables log time stamps.

          • log uptimeEnables time stamps on log messages, showing the time since the system was rebooted.
          • log datetimeEnables time stamps on log messages. Depending on the options selected, the time stamp can include the date, time in milliseconds relative to the local time zone, and the time zone name.
           
          Step 3 end


          Example:
          Switch(config)# end
          
          
           

          Returns to privileged EXEC mode.

           

          Enabling and Disabling Sequence Numbers in Log Messages

          If there is more than one log message with the same time stamp, you can display messages with sequence numbers to view these messages. By default, sequence numbers in log messages are not displayed.

          This task is optional.

          SUMMARY STEPS

            1.    configure terminal

            2.    service sequence-numbers

            3.    end


          DETAILED STEPS
              Command or Action Purpose
            Step 1 configure terminal


            Example:
            Switch# configure terminal
            
            
             

            Enters global configuration mode.

             
            Step 2 service sequence-numbers


            Example:
            Switch(config)# service sequence-numbers
            
            
             

            Enables sequence numbers.

             
            Step 3 end


            Example:
            Switch(config)# end
            
            
             

            Returns to privileged EXEC mode.

             

            Defining the Message Severity Level

            Limit messages displayed to the selected device by specifying the severity level of the message.

            This task is optional.

            SUMMARY STEPS

              1.    configure terminal

              2.    logging console level

              3.    logging monitor level

              4.    logging trap level

              5.    end


            DETAILED STEPS
                Command or Action Purpose
              Step 1 configure terminal


              Example:
              Switch# configure terminal
              
              
               

              Enters global configuration mode.

               
              Step 2 logging console level


              Example:
              Switch(config)# logging console 3
              
              
               

              Limits messages logged to the console.

              By default, the console receives debugging messages and numerically lower levels.

               
              Step 3 logging monitor level


              Example:
              Switch(config)# logging monitor 3
              
              
               

              Limits messages logged to the terminal lines.

              By default, the terminal receives debugging messages and numerically lower levels.

               
              Step 4 logging trap level


              Example:
              Switch(config)# logging trap 3
              
              
               

              Limits messages logged to the syslog servers.

              By default, syslog servers receive informational messages and numerically lower levels.

               
              Step 5 end


              Example:
              Switch(config)# end
              
              
               

              Returns to privileged EXEC mode.

               

              Limiting Syslog Messages Sent to the History Table and to SNMP

              This task explains how to limit syslog messages that are sent to the history table and to SNMP.

              This task is optional.

              SUMMARY STEPS

                1.    configure terminal

                2.    logging history level

                3.    logging history size number

                4.    end


              DETAILED STEPS
                  Command or Action Purpose
                Step 1 configure terminal


                Example:
                Switch# configure terminal
                
                
                 

                Enters global configuration mode.

                 
                Step 2 logging history level


                Example:
                Switch(config)# logging history 3
                
                
                 

                Changes the default level of syslog messages stored in the history file and sent to the SNMP server.

                By default, warnings, errors, critical, alerts, and emergencies messages are sent.

                 
                Step 3 logging history size number


                Example:
                Switch(config)# logging history size 200
                
                
                 

                Specifies the number of syslog messages that can be stored in the history table.

                The default is to store one message. The range is 0 to 500 messages.

                 
                Step 4 end


                Example:
                Switch(config)# end
                
                
                 

                Returns to privileged EXEC mode.

                 

                Logging Messages to a UNIX Syslog Daemon

                This task is optional.


                Note


                Some recent versions of UNIX syslog daemons no longer accept by default syslog packets from the network. If this is the case with your system, use the UNIX man syslogd command to decide what options must be added to or removed from the syslog command line to enable logging of remote syslog messages.


                Before You Begin
                • Log in as root.
                • Before you can send system log messages to a UNIX syslog server, you must configure the syslog daemon on a UNIX server.
                SUMMARY STEPS

                  1.    Add a line to the file /etc/syslog.conf.

                  2.    Enter these commands at the UNIX shell prompt.

                  3.    Make sure the syslog daemon reads the new changes.


                DETAILED STEPS
                    Command or Action Purpose
                  Step 1 Add a line to the file /etc/syslog.conf.

                  Example:
                  local7.debug /usr/adm/logs/cisco.log
                  
                  
                   
                  • local7Specifies the logging facility.
                  • debugSpecifies the syslog level. The file must already exist, and the syslog daemon must have permission to write to it.
                   
                  Step 2 Enter these commands at the UNIX shell prompt.

                  Example:
                  $ touch /var/log/cisco.log
                  $ chmod 666 /var/log/cisco.log
                  
                  
                   

                  Creates the log file. The syslog daemon sends messages at this level or at a more severe level to this file.

                   
                  Step 3 Make sure the syslog daemon reads the new changes.

                  Example:
                  $ kill -HUP `cat /etc/syslog.pid`
                  
                  
                   

                  For more information, see the man syslog.conf and man syslogd commands on your UNIX system.

                   

                  Monitoring and Maintaining System Message Logs

                  Monitoring Configuration Archive Logs

                  Command

                  Purpose

                  show archive log config {all | number [end-number] | user username [session number] number [end-number] | statistics} [provisioning]

                  Displays the entire configuration log or the log for specified parameters.

                  Configuration Examples for System Message Logs

                  Example: Stacking System Message

                  This example shows a partial switch system message for active switch and a stack member (hostname Switch-2):

                  00:00:46: %LINK-3-UPDOWN: Interface Port-channel1, changed state to up
                  00:00:47: %LINK-3-UPDOWN: Interface GigabitEthernet1/0/1, changed state to up
                  00:00:47: %LINK-3-UPDOWN: Interface GigabitEthernet1/0/2, changed state to up
                  00:00:48: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan1, changed state to down 
                  00:00:48: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet1/0/1, changed state to down 2 
                  *Mar  1 18:46:11: %SYS-5-CONFIG_I: Configured from console by vty2 (10.34.195.36)
                  18:47:02: %SYS-5-CONFIG_I: Configured from console by vty2 (10.34.195.36)
                  *Mar  1 18:48:50.483 UTC: %SYS-5-CONFIG_I: Configured from console by vty2 (10.34.195.36) 
                  
                  00:00:46: %LINK-3-UPDOWN: Interface Port-channel1, changed state to up (Switch-2)
                  00:00:47: %LINK-3-UPDOWN: Interface GigabitEthernet2/0/1, changed state to up (Switch-2)
                  00:00:47: %LINK-3-UPDOWN: Interface GigabitEthernet2/0/2, changed state to up (Switch-2)
                  00:00:48: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan1, changed state to down (Switch-2)
                  00:00:48: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet2/0/1, changed state to down 2 (Switch-2)
                  
                  

                  Example: Switch System Message

                  This example shows a partial switch system message on a switch:

                  00:00:46: %LINK-3-UPDOWN: Interface Port-channel1, changed state to up
                  00:00:47: %LINK-3-UPDOWN: Interface GigabitEthernet0/1, changed state to up
                  00:00:47: %LINK-3-UPDOWN: Interface GigabitEthernet0/2, changed state to up
                  00:00:48: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan1, changed state to down
                  00:00:48: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/1, changed state to down 2
                  *Mar  1 18:46:11: %SYS-5-CONFIG_I: Configured from console by vty2 (10.34.195.36)
                  18:47:02: %SYS-5-CONFIG_I: Configured from console by vty2 (10.34.195.36)
                  *Mar  1 18:48:50.483 UTC: %SYS-5-CONFIG_I: Configured from console by vty2 (10.34.195.36) 
                  
                  

                  Additional References for System Message Logs

                  Related Documents

                  Related Topic Document Title

                  System management commands

                  System Management Command Reference (Catalyst 3850 Switches)

                  Platform-independent command references

                  Configuration Fundamentals Command Reference, Cisco IOS XE Release 3S (Catalyst 3850 Switches)

                  Platform-independent configuration information

                  Configuration Fundamentals Configuration Guide, Cisco IOS XE Release 3S (Catalyst 3850 Switches)

                  IP Addressing Configuration Guide Library, Cisco IOS XE Release 3S (Catalyst 3850 Switches)

                  Standards and RFCs

                  Standard/RFC Title
                  None

                  MIBs

                  MIB MIBs Link

                  All supported MIBs for this release.

                  To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

                  http:/​/​www.cisco.com/​go/​mibs

                  Technical Assistance

                  Description Link

                  The Cisco Support website provides extensive online resources, including documentation and tools for troubleshooting and resolving technical issues with Cisco products and technologies.

                  To receive security and technical information about your products, you can subscribe to various services, such as the Product Alert Tool (accessed from Field Notices), the Cisco Technical Services Newsletter, and Really Simple Syndication (RSS) Feeds.

                  Access to most tools on the Cisco Support website requires a Cisco.com user ID and password.

                  http:/​/​www.cisco.com/​support

                  Feature History and Information For System Message Logs

                  Release

                  Modification

                  Cisco IOS XE 3.2SE

                  This feature was introduced.