The Confreg Cisco command

The ‘confreg’ command in Cisco networks is a powerful tool used for configuring various settings related to the network’s hardware, operating system, and routing protocols. Here’s a detailed explanation:

Purpose:

The primary purpose of the ‘confreg’ command is to make changes to the device’s configuration register. The configuration register is a special area in the device’s memory that stores important settings and parameters that control the device’s behavior. By modifying these settings, you can influence the device’s functionality and performance.

Usage:

The basic syntax of the ‘confreg’ command is as follows:

confreg [ register-name ] [ value ] [ confirm ]

Parameters:

1. register-name: This parameter specifies the name of the configuration register that you want to modify. Cisco devices have various configuration registers, each with a specific purpose. Some common register names include:
   • ‘config-register’: Used to configure general system parameters.
   • ‘interface-config-register’: Used to configure interface-specific settings.
   • ‘routing-config-register’: Used to configure routing protocols and parameters.
2. value: This parameter specifies the new value that you want to assign to the configuration register. The value can be a binary number, a hexadecimal number, or a keyword that corresponds to a specific setting.
3. confirm: This optional parameter is used to confirm the changes before they are applied to the device. When you include the ‘confirm’ keyword, the device will prompt you to confirm the changes before making them permanent.

Example:

To configure the configuration register on a Cisco router to disable the console password recovery feature, you would use the following command:

confreg config-register 0x2102 confirm

In this example, the ‘config-register’ register is being modified, and the ‘0x2102’ value disables the console password recovery feature.

Equipment Compatibility:

The ‘confreg’ command is supported on a wide range of Cisco networking equipment, including routers, switches, and firewalls. However, the specific configuration registers available and the supported values may vary depending on the device model and IOS version. It is essential to refer to the device’s documentation or use the ‘show confreg’ command to determine the available configuration registers and their supported values.

Benefits of Using ‘confreg’:

1. Fine-Grained Control: The ‘confreg’ command allows you to make precise changes to the device’s configuration register, enabling you to customize the device’s behavior and optimize its performance.
2. Advanced Configuration: The ‘confreg’ command provides access to advanced configuration options that are not available through the standard configuration commands. These options can be useful for troubleshooting, performance tuning, and implementing specific features.
3. Device Recovery: In some cases, the ‘confreg’ command can be used to recover a device from a boot failure or a corrupted configuration. By modifying the configuration register, you can direct the device to load a specific configuration file or enter a recovery mode.

Caution:

The ‘confreg’ command is a powerful tool, and using it incorrectly can lead to device malfunctions or security vulnerabilities. It is essential to have a thorough understanding of the configuration register and its impact on the device’s behavior before using the ‘confreg’ command. Always refer to the device’s documentation and use the ‘show confreg’ command to verify the current configuration before making changes.

confreg Usage Examples

The confreg command in Cisco is used to configure default values for registers on network modules and interface processors. It allows you to specify the default values for various register settings, which can be applied to all instances of a particular module or interface processor.

The syntax for the ‘confreg’ command is as follows:

confreg [module] [reg_type] [reg_num] [value]

Here are some examples of how the ‘confreg’ command can be used:

1. Set the default value of register 10 on all WIC-1T modules to 0x1234:

confreg WIC-1T register 10 0x1234

1. Set the default value of register 20 on the first instance of the NM-16ESW module to 0x5678:

confreg NM-16ESW 1 register 20 0x5678

1. Set the default value of register 30 on all GE-45032 interface processors to 0x9ABC:

confreg GE-45032 register 30 0x9ABC

1. Clear the default value of register 40 on all WIC-2T modules:

confreg WIC-2T register 40 default

1. Display the current default values for all registers on the first instance of the NM-16ESW module:

confreg NM-16ESW 1 register show

1. Display the current default value for register 50 on all GE-XFP interface processors:

confreg GE-XFP register 50 show

1. Restore the default values for all registers on all modules and interface processors to their factory default settings:

confreg factory-default

Note: The ‘confreg’ command is a privileged EXEC command and requires appropriate authorization to use. Additionally, the availability of this command and the specific registers that can be configured may vary depending on the Cisco device model and IOS version.