Monitoring Troubleshooting an OSPF Network | OSPF Network Design Solutions

Table of Contents

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

Table of Contents