What is Confreg in a Cisco router?

What is Confreg in a Cisco router?

Configuration Register is a special 16 bits value that can be configured in Cisco routers. It is mainly used in three cases; To determine how the router boots. To determine boot options.

What is Confreg 0x2102?

The factory-default setting for the configuration register is 0x2102. This indicates that the router should attempt to load a Cisco IOS software image from Flash memory and load the startup configuration.

How do I get into Cisco ROMmon mode?

Press break on the terminal keyboard within 1 minute of power up in order to the router into ROMmon. Enter in confreg 0x2142 at the rommon 1> prompot in order to boot the from Flash.

How do I get my router out of ROMmon mode?

If your router gets stuck in ROMmon mode during the boot process, examine the value of the configuration register by entering the confreg command. Change the value of the configuration register as shown below to stop the router to go into the ROMmon mode after reloading.

What is config register 0xf?

Config-Register is basically a hexadecimal or decimal value that represents. the 16-bit configuration register value that will be used the next time the switch is. restarted. The value range is from 0x0 to 0xFFFF (0 to 65535 in decimal).

What does the command Confreg 0x2142 provide?

Explanation: The default configuration setting is 0x2102, which tells the router to load the IOS from flash and the configuration from NVRAM. 0x2142 tells the router to bypass the configuration in NVRAM so that you can perform password recovery.

What is configuration register is 0x102?

The most common configuration register settings are 0x102 and 0x2102. When the configuration register is set to 0x0102, it has the Break key disabled when the router is operating, and it looks into the configuration to determine the boot sequence.

What is Rommon mode in Cisco router?

The ROM Monitor (ROMMON) is a bootstrap program that initializes the hardware and boots the Cisco IOS XE software when you power on or reload a router. If your router does not find a valid system image to load when it is booting, the system enters the ROMMON mode.

How do I restore my Cisco 1841 router from Rommon mode?

Password Recovery for Cisco Router 1841

1. If you can access the router use the show version command.
2. Cycle power to the router and within 60 seconds enter the break sequence to enter ROMMON.
3. Enter confreg 0x2142 at the rommon 1> prompt to boot from flash.
4. Enter reset at the rommon 2> prompt to reboot the router.

Which command will show you the IOS version running on your router?

The best answer is show version, which shows you the IOS file running currently on your router. The show flash command shows you the contents of flash memory, not which file is running.

What is boot system command?

The boot system command allows you to specify not only which IOS images to boot from, but also the order to try them in if it has trouble booting. In the example, this router will try a succession of three different IOS images. If they all fail, it will resort to using its boot ROM image.

How to change configuration register in ROMMON mode?

This can be done both in Rommon mode and in configuration mode. In Rommon mode, it can be change with “ confreg ” command. Below, we are changing Configuration Register as 0x2142.

Why does my Cisco router keep booting up in ROMMON?

It goes back to ROMmon because the router’s Cisco IOS software image and bootflash image are both corrupt. Since you have already determined that the cause of the router booting up in ROMmon is not due to the configuration register value, the only option available for recovery is to re-install or upgrade the Cisco IOS software.

How do I use the ROM monitor on my Cisco router?

If there is no Cisco IOS software image loaded on the router, the ROM monitor runs the router. To use the ROM monitor, you must be using a terminal or PC that is connected to the router over the console port. Perform these steps to configure the router to boot up in ROM monitor mode the next time it is rebooted.

What happens when a Cisco router exit global configuration mode?

Exits global configuration mode. Reboots the router with the new configuration register value. The router remains in ROM monitor and does not boot the Cisco IOS software. As long as the configuration value is 0x0, you must manually boot the operating system from the console.