Troubleshooting of Cisco high-End Routers

I. fault phenomena and handling

The organization uses the Cisco7513 router as the WAN backbone router and adopts the standard configuration. The IOS version is 11.1. The 2 m main egress line protocol of the vro is found to be down on a single day, resulting in network interruptions associated with the vro. Run the "show running-config" command to check all running parameters. No error is found; run the "show interfaces serial" command to check the serial port and find that some ports are in the up status while the line protocol is down. In this case, the serial ports are on the same serial port Board (a board, other modules work normally. After checking that all physical lines are normal, the possibility of line faults is ruled out. However, in general, it is not likely that the serial port on the same serial port board experiences line faults at the same time. At this point, we can preliminarily determine that a board may be faulty. When you enter the global configuration mode and try to enter the port configuration mode of the serial port on the board, you will find that this cannot be achieved. Every time you type "interface serial port number", an error will always be reported, however, the same command can enter the port configuration mode of other serial ports. At this time, we can preliminarily determine that there is a software fault in IOS itself. After restarting the router with the reload command, the system enters the ROMmonitor mode and the prompt is "rommon> ", enter the command "boot" to start the vro, but the fault still exists, and all the configuration statements on the-board serial port are reported as errors.

When the router is powered off and powered on, it is observed that the AC (or DC) OK LED lights of the router are green, which indicates that the power supply subsystem of the system works normally, the fan rotates properly and the output of the wrong LED light is not on. This indicates that the cooling sub-system works normally, and the LED light of the route switching processor (RSP) is green, which also indicates that the system works properly. The Enable LED lights of each interface are green, indicating that the RSP has completed the initialization of the interface processor. However, the LED lights on board a are all flushed and destroyed. After the "reset" command is executed and the system is guided by "boot", all the configuration statements on the serial port on board a disappear.

When we further examined board a, we found that its model was VIP2, and only one four serial ports sub-module was installed on the two sub-modules. Therefore, there were only four serial ports on board a (which can be expanded to eight ), three serial ports are in use and one is idle. Normally, the LED lights of the three serial ports should be on, but the LED lights of the unused serial ports should be yellow, but the LEDs of the Four serial ports are not on at present. After the system starts, run the "show version" command to find that the system has found the board and identified the model of the Board as VIP2, but there is no details. To further compress the fault, switch the board to the slot for installation, and the fault still exists. When the Board is installed on another machine without failure, everything works normally.

The preceding steps compress the fault to the router configuration parameters. Run the "show version" command again. In the last line of the display information, the value of the router configuration register is 0x0. Change it to 0x2102 and then reboot the router, after the backup configuration is renewed from the tftpserver into running-config, the router works back to normal. So far, this failure that seems to be damaged by the hardware interface and is caused by incorrect software parameter settings is ruled out.

Ii. Fault Cause Analysis

The register values of series of high-end vrouters such as 72 and 75 are composed of four hexadecimal numbers. The low four digits determine the system startup mode:

When the minimum 4 bits is 0-0-0-0, the vro does not load the system image, but enters the monitoring status (ROM monitor mode) or Maintenance status (Maintenance mode). Manual guidance is required.

When the minimum four digits are 0-0-0-1, the router loads the system image found from ROMs.

When the minimum 4 bits are between 0-0-1-0 and 1-1-1-1, the router loads the operating SYSTEM image according to the boot system command settings in the startup configuration, if this command is not set, the operating system image is loaded from the system image on a default network server.

When the 6th-bit value is 1, the configurations in NVRAM are ignored when the vro starts. For example:

0x0: the operating system image is not automatically loaded, but enters the ROM monitor mode and waits for the user to enter the command (for example, if the command fails in the preceding example, the system can only boot the system and cannot load the interface module IOS); 0xf: load the operating system image (Cisco 72 Series, Cisco75 series, etc., not from ROM) from a system image on a default network server by running commands in the startup configuration ). 0x101: Disable break Jian and direct the boot from ROM. 0x2102: Usually the reference value. 0x2142: Ignore startup-config at startup. Here is an example of automatic boot from flash memory: Router # configure terminalRouter (config) # boot system flash gsnew-imageRouter (config) # config-register 0x010f ^ Router # copy running-config startup-config [OK] Router # reload [confirm]

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