Use cisco rommon to maintain a router

For many beginners, using cisco rommon to maintain a vro, the ROM Monitor of a cisco router is often unfamiliar or even daunting. The reason is simple. First, we do not often use this mode, I am not familiar with the related operations. Second, Operation errors in ROM Monitor mode often cause fatal damage to the vro (such as destroying the IOS file in flash, leading to system crash .), As a result, many people are reluctant to stick to it. In fact, ROM Monitor is not complex. It is only a low-level operating system of the cisco router, which is usually used for testing and troubleshooting. It can be done easily with little time. Next, I will take the two most common cases of using ROM Monitor in my actual work as an example. I hope to introduce myself to readers! Www.2cto.com scenario 1: The vro password is restored to prevent others from knowing the vro password (especially the privileged password) and threaten the security of the local network. Therefore, many administrators have complicated the password. However, after configuring the vro, we seldom operate on the vro. After a while, when we need to configure the vro, the password may be lost. At this time, we only need a PC (OS is windows series), a console cable and the corresponding interface converter, and we are next to the router. Then follow the steps below to make it easy. 1. Set the Super Terminal of the PC so that we can use the console port of the router to directly operate the router. Note: because the process is very simple, I will omit it to save space. 2. Start the vro and press the break or ctrl + break Key in the first 60 seconds to enter the ROM Monitor mode of the vro. Www.2cto.com 3. Next we will give a brief description of the cisco 2600 series routers most commonly used by beginners. System Bootstrap, Version 11.3 (2) XA4, release software (fc1) Copyright (c) 1999 by cisco Systems, Inc. TAC: Home: SW: IOS: Specials for infoC2600 platform with 32768 Kbytes of main memory (this vro is a 2600 series vro) (press ctrl + break to enter the ROM Monitor mode) rommon 1>? Note: can we use? Or help command to view the commands that can be used in this mode. Alias set and display aliases commandboot boot up an external processbreak set/show/clear the breakpointconfreg configuration register utilitycont continue executing a downloaded image ...... (Multiple rows are omitted) reset system resetset display the monitor variablesstack produce a stack tracesync write monitor environment to NVRAMsysret print out info from last system reset tftp image reset unset an aliasunset unset a monitor variablexmodem x/ymodem image download rommon 2> confreg 0x2142 note: use this command to modify the value of the configuration register of the vro so that the vro does not load the startup configuration during the next restart. This skips the authentication of the user password and the privileged password and enters the privileged mode. You must reset or power cycle for new config to take advantage of trommon 3> reset Note: Use this command to restart the vro System Bootstrap, Version 11.3 (2) XA4, release software (fc1) copyright (c) 1999 by cisco Systems, Inc. TAC: Home: SW: IOS: Specials for infoC2600 platform with 32768 Kbytes of main memoryprogram load complete, entry point: 0x80008000, size: 0x487758Self decompressing the image: ##################################### ######################################## ######################################## ########### (The following startup process is omitted) --- System Configuration Dialog --- wocould you like to enter the initial configuration dialog? [Yes/no]: n Note: Select no to directly enter the CLI mode Press RETURN to get started! (Press ENTER) Router> enRouter # Note: run the show version command to check that the value of the configuration register is 0x2142. router # copy star run Note: Use this command to load the startup configuration and set a new password. If this step is not performed, the new password fails to be set after the next restart. Www.2cto.com Router # conf tRouter (config) # config-register 0x2102 note: the startup configuration will be loaded when the Router restarts next time. You need to use a new password to verify the Router (config) # endRouter # copy run star Note: Save the running configuration to start configuring Destination filename [startup-config]? Building configuration... [OK] prompt: The password recovery of cisco2500, 2000, 3000, 4000, and 7000 Series routers is basically the same as the above operations, the main difference is that the command for modifying the configuration register is "o/r 0x2142" and the restart command is "I". The routers of other series are basically the same as those of the 2600 series.