Monitoring Troubleshooting an OSPF Network

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To limit messages logged to the console based on severity, use the logging console global configuration command. The no form of this command disables logging to the console terminal.

    logging console level    no logging console 

Specifying a level causes messages at that level and numerically lower levels to be displayed at the console terminal. Table 8-16 shows these priority levels.

Table 8-16 Logging message priorities
Level Name Level Level Description SYSLOG Definition

emergencies 0 System unusable 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


TIPS:  
The effect of the log keyword with the ip access-list (extended) command depends on the setting of the logging console command. The log keyword takes effect only if the logging console level is set to 6 or 7. If you change the default to a level lower than 6 and specify the log keyword with the ip access-list (extended) command, no information is logged or displayed. Although you cannot specify your level numerically in the router, it must be done textually:
    OSPF_Core(config)#logging console ?      alerts         Immediate action needed      critical       Critical conditions      debugging      Debugging messages      emergencies    System is unusable      errors         Error conditions      informational  Informational messages      notifications  Normal but significant conditions      warnings       Warning conditions 

The EXEC command show logging displays the addresses and levels associated with the current logging setup, as well as any other logging statistics. The following example shows a wide variety of events that can be reflected within the router’s log file.

    OSPF_Router# show logging    Syslog logging: enabled (0 messages dropped, 0 flushes, 0 overruns)        Console logging: level debugging, 66 messages logged        Monitor logging: level debugging, 0 messages logged        Trap logging: level informational, 70 message lines logged    %QUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier. Transceiver problem?    %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0, changed state    to down    %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state    to down    %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1, changed state    to down    *Mar 1 00:00:08 UTC: %LINK-3-UPDOWN: Interface Ethernet0, changed state    to up    *Mar 1 00:00:08 GMT: %LINK-3-UPDOWN: Interface Serial0, changed state    to down    *Mar 1 00:00:08 GMT: %LINK-3-UPDOWN: Interface Serial1, changed state    to down    *Mar 1 00:00:09 GMT: %LINEPROTO-5-UPDOWN: Line protocol on Interface    Loopback0, changed state to up    *Mar 1 00:00:10 GMT: %LINEPROTO-5-UPDOWN: Line protocol on Interface    Serial0.1, changed state to down    *Mar 1 00:00:12 GMT: %LINK-5-CHANGED: Interface Serial1, changed state    to administratively down    *Mar 1 00:00:12 GMT: %SYS-5-CONFIG_I: Configured from memory by console    *Mar 1 00:00:12 GMT: %SYS-5-RESTART: System restarted —    Cisco Internetwork Operating System Software    IOS (tm) 1600 Software (C1600-Y-L), Version 11.1(7)AA, EARLY DEPLOYMENT    RELEASE SOFTWARE (fc2)    Copyright (c) 1986-1996 by cisco Systems, Inc.    Compiled Thu 24-Oct-96 02:26 by kuong    *Mar 1 00:01:08 GMT: %QUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier.    Transceiver problem?    *Mar 1 00:02:07 GMT: %QUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier.    Transceiver problem?    *Mar 1 00:03:07 GMT: %QUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier.    Transceiver problem?    *Mar 1 00:04:06 GMT: %QUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier.    Transceiver problem?    *Mar 1 00:05:06 GMT: %QUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier.    Transceiver problem?    *Mar 1 00:06:06 GMT: %QUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier.    Transceiver problem?    *Mar 1 00:07:05 GMT: %QUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier.    Transceiver problem?    *Mar 1 00:49:50 GMT: %QUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier.    Transceiver problem?    *Mar 1 00:50:21 GMT: %SYS-5-CONFIG_I: Configured from console by    console    *Mar 1 00:50:49 GMT: %QUICC_ETHER-1-LOSTCARR: Unit 0, lost carrier.    Transceiver problem?    *Mar 1 00:51:43 GMT: %SYS-5-CONFIG_I: Configured from console by    console    *Mar 1 00:51:43 GMT: %LINK-5-CHANGED: Interface Ethernet0, changed state    to administratively down 

Notice the first four lines after the header start with % followed by system error information, then a brief English statement of the event being logged. Within the system error information is a number with hyphens of either side of it. This number corresponds to the levels as shown in Table 8-16.

Date and Time Stamping

In the preceding example, the first four lines are not date and time stamped. When did those events occur? Did they happen recently? Are they related to problems that are now occurring within the network? Unless you were closely monitoring events in the SYSLOG, it is unlikely that you would be able to answer these questions. The remaining SYSLOG entries are stamped with the month, date, hour, minute, second, and timezone (programmed into the router) of when the event occurred.

As is readily apparent throughout the remainder of the example, having this information before each entry would be of great benefit when using the SYSLOG entries to assist you in troubleshooting. For instance, in the preceding example, consider that shortly after midnight this router went down for no apparent reason and severe network impact resulted. One of the first questions you will need to answer is why did this happen? This answer is readily found in the router’s SYSLOG as shown in the following example.

    *Mar 1 00:00:12 GMT: %SYS-5-RESTART: System restarted —    Cisco Internetwork Operating System Software    IOS (tm) 1600 Software (C1600-Y-L), Version 11.1(7)AA, EARLY            DEPLOYMENT RELEASE SOFTWARE (fc2)    Copyright (c) 1986-1996 by cisco Systems, Inc.    Compiled Thu 24-Oct-96 02:26 by kuong 


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OSPF Network Design Solutions
OSPF Network Design Solutions
ISBN: 1578700469
EAN: 2147483647
Year: 1998
Pages: 200
Authors: Tom Thomas

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