On high-end Cisco router troubleshooting skills – routers, skills, troubleshooting – Communications Industry
1, fault behavior and treatment Units Cisco7513 Router As a wide area network backbone routers, using the standard configuration, IOS version 11.1. 2M day found that the router is down main export line protocol status, so that network disruption associated with using "showrunning-config" command check all operating parameters and found no error; also used "showinterfacesserial" command checks the serial port, found that certain port status up, and the line protocol is down, and this occurs both in the same serial port serial board (A board), the other modules working correctly. The investigation also normal for all the physical lines, thus excluding the possibility of a line fault. However, in general, the same below-board serial port of a serial line fault occurs at the same time the possibility is not great. Thus the initial identification of possible A board can be a problem. When to enter global configuration mode, think of into the A-board serial port configuration mode to find the impossible, every type "interfaceserial serial number", always error, but the same order they can enter the other serial port configuration mode. At this time, preliminary judgments can arise in certain IOS software failure, restart the router with the reload command after the system into ROMmonitor mode, prompt for the "rommon>", type the command "boot" to activate the router, but the fault persists, and all A board serial port configuration statement that all error.
Then router and then power off when power is observed: the exchange of the router (or DC) OKLED light green, indicating that the system's power supply subsystem is working properly, the fan rotation normal and the output error LED lights are not bright, indicating that cooling subsystem is working properly, Route Switch Processor (RSP) of the LED light is green, which means that the system is working properly. The interface EnableLED light is green, the RSP has completed the initialization of the interface processor. A panel of LED lights, but all flashed on the off, implementation of the "reset" command then "boot" after the boot system configuration for all serial port A board statement all disappeared. A board
further examination found his model for the VIP2, the two sub-modules on which only the installation of a four-port sub-module, so A board only four strings (expandable to 8), three serial have been used, an idle. Normal use of the serial port of the three LED lights should be bright, without using the serial port of the LED light should be yellow, but there are four serial port LED is off. The system boots, use the command "showversion" can be found A board system has been found and identified the board's model VIP2, but no details. To further reduce the fault, will swap slot A board installed, the fault persists; the A board installed in another trouble-free machine, then everything is normal.
The above steps, will be compressed to a fault on the router configuration parameters. Then "showversion" command, the last line in the display information and found the router configuration register value is 0x0, be amended to 0x2102 after the reboot the router, the backup configuration from tftpserver copyed running-config, the router back to normal work , thus excluding the damage looks like real hardware interface for the software fault parameter is set wrong.
II, Failure Analysis 72,75 series high-end routers register value of 16 hexadecimal numbers by four, of which 4 will decide on a low-start method:
When a minimum four to 0-0-0-0, the router does not load the system image, but into the monitor state (ROMmonitormode) or maintenance of state (Maintenancemode), need for manual guidance.
When a minimum four to 0-0-0-1, the router load ROMs found from the system image.
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