Rom Monitor Overview And Basic Procedures; Rom Monitor Overview - Cisco 900 Series Hardware Installation Manual

ROM Monitor Overview and Basic Procedures

The ROM Monitor (ROMMON) is a bootstrap program that initializes the hardware and boots the Cisco 900
ISR 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. ROMMON mode can also be accessed by interrupting the boot sequence during startup.
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ROM Monitor Overview

The ROM Monitor software is also known as ROMMON, boot software, boot image, or boot helper. Although
it is distributed with routers that use the Cisco IOS software, the ROMMON is a separate program from the
Cisco IOS software. During normal startup, ROMMON initializes the router, and then, the control passes to
the Cisco IOS software.
When you connect a terminal to the router that is in ROMMON mode, the ROMMON command-line interface
(CLI) prompt is displayed.
Access the ROMMON mode to perform these tasks:
• Specify config-register value to use for the next boot up
• Boot a valid IOS image
• Bypass NVRAM settings and config-register value for password recovery
Note
After the Cisco IOS software boots up, ROMMON is no longer in use.
Environmental Variables and the Configuration Register
Two primary connections exist between ROMMON and the Cisco IOS software: the ROMMON environment
variables and the configuration register.
The ROMMON environment variables define the location of the Cisco IOS software and describe how to
load it. After ROMMON has initialized the router, it uses the environment variables to locate and load the
Cisco IOS software.
ROM Monitor Overview, on page 33
Hardware Installation Guide for the Cisco 900 Series Integrated Services Router
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