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CCNA 7.3.d: Logging

Overview:

Logging is essential to gaining visibility into your network

 

Study Notes:

  • By default, system logging  is enabled to the console at the debugging level
  • Log messages are displayed in this format
Seq_no:timestamp: %facility-severity-MNEMONIC:description
  • For example:
000052: Jan 20 08:50:18: %SYS-5-CONFIG_I: Configured from console by vty2 (172.16.0.25)
  • Five types of logging
    • Console logging - logs are visible to users who are consoled in
    • Terminal logging - logs are visible to users who are connected via VTY lines
    • Buffered logging - logs are written to the buffer whose size is configurable
    • Syslog logging - logs are forwarded to an external syslog server
    • SNMP logging - logs are forwarded to an external SNMP server via traps
  • Eight levels of logging
    • 0 - Emergencies
    • 1 - Alerts
    • 2 - Critical
    • 3 - Errors
    • 4 - Warnings
    • 5 - Notifications
    • 6 - Information
    • 7 - Debugging
Level Keyword Level Description Syslog Definition
emergencies 0 System unstable LOG_EMERG
alerts 1 Immediate action needed LOG_ALERT
critical 2 Critical conditions LOG_CRIT
errors 3 Error conditions LOG_ERR
warnings 4 Warning conditions LOG_WARNING
notifications 5 Normal but significant condition LOG_NOTICE
informational 6 Informational messages only LOG_INFO
debugging 7 Debugging messages LOG_DEBUG

 

  • Logging rate limits can be set so as not to overwhelm the processor of the router with log messages

Sample logging configuration:

Router#config t
Router(config)#logging on
Router(config)#service timestamps log datetime [msec] [localtime] [show-timezone]
Router(config)#service sequence-numbers
Router(config)#logging buffered 16483
Router(config)#logging <ip.of.syslog.server>
Router(config)#logging console <level>
Router(config)#logging monitor <level>
Router(config)#logging trap <level>
Router(config)#logging history <level>
Router(config)#logging history size <1 to 500>
Router(config)#logging rate-limit <seconds> all except <level>
Router(config)#end
Router#terminal monitor
Router#show running-config
Router#show logging
Router#show logging history

 

PacketTracer Lab: CCNA-7.3.d-Logging.pkt

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