Cisco Updated 100-490 Exam Questions and Answers by brian

The configuration register on Cisco routers and switches controls specific bootup behaviors. Here's how to modify it:

1. In ROMmon Mode:

rommon>confreg 0x2102 : This command is used when the device is in ROMmon mode (a basic operating system loaded when the full Cisco IOS cannot be found). ROMmon offers limited functionality and is often used for troubleshooting or password recovery.

2. In Global Configuration Mode:

router(config)#config-register 0x2102 : This command is used from within the Cisco IOS itself when you have normal access to the router. You would enter privileged EXEC mode and then global configuration mode to use it.

Importance of Configuration Register Settings:

The most common reasons to modify the configuration register are:

Password Recovery: Setting the configuration register to 0x2142 tells the router to ignore the startup configuration (stored in NVRAM), allowing you to bypass password protection.

Changing Boot Behavior: Settings can control the boot sequence, such as specifying where the Cisco IOS image should be loaded from.

References:

Cisco Configuration Register: https://www.cisco.com/c/en/us/support/docs/routers/10000-series-routers/50421-config-register-use.html

Understanding the Configuration Register (Cisco): https://networklessons.com/cisco/ccna-routing-switching-icnd1-100-105/configuration-register-cisco-ios

When deploying Cisco Catalyst 3850 Series switches, there are two modes of operation to choose from: Install mode and Bundle mode. Install mode is the default mode for the switch and uses a package-provisioning file named packages.conf to boot the switch. It allows for a more complete set of features and requires fewer resources upon boot1. Bundle mode, on the other hand, is similar to using traditional monolithic Cisco IOS images to boot the switch. It consumes more memory than Install mode because the packages are extracted from the bundle and copied to the RAM2. Cisco recommends using Install mode for operation due to its efficiency and feature set2.

The show version command on Cisco devices provides a variety of system information, including:

Cisco IOS version: The version of the Cisco IOS software running on the device.

Boot image: The location of the IOS image used during startup.

Hardware information: Model, processor type, memory details.

Interfaces: A list of the device's interfaces.

Configuration register: The current value of the configuration register, typically displayed near the end of the output.

Why other options are incorrect:

show flash: Displays the contents of flash memory, but not the configuration register.

show running-config: Displays the currently active configuration, but the configuration register setting is not directly part of the running configuration.

show config-register: This is not a standard Cisco IOS command.

The show cdp neighbor command on Cisco devices displays various pieces of information about directly connected neighboring devices that support Cisco Discovery Protocol (CDP). Two key pieces of information displayed by this command are the platform of the neighboring device, which indicates the hardware type, and the device ID, which is typically the hostname of the device1. The command does not display the uptime or the Cisco IOS Software version; these details can be seen with the show cdp neighbor detail command. The IP address is also part of the detailed information and not displayed in the standard show cdp neighbor output1.