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This chapter provides an overview of ROM Monitor concepts and operations.
The ROM Monitor is a bootstrap program that initializes the hardware and boots the Cisco IOS XE software when you power on or reload a router. When you connect a terminal to the router that is in ROM Monitor mode, the ROM Monitor command-line interface (CLI) prompt is displayed.
During normal operation, users do not use ROM Monitor mode. ROM Monitor mode is used only in special circumstances, such as reinstalling the entire software set, resetting the router password, or specifying a configuration file to use at startup.
The ROM Monitor software is known by many names. It is sometimes called ROMMON because of the CLI prompt in ROM Monitor mode. The ROM Monitor software is also called the boot software , boot image , or boot helper . Although it is distributed with routers that use the Cisco IOS XE software, ROM Monitor is a separate program from the Cisco IOS XE software. During normal startup, the ROM Monitor initializes the router, and then control passes to the Cisco IOS XE software. After the Cisco IOS XE software takes over, the ROM Monitor is no longer in use.
Environmental Variables and the Configuration Register
Two primary connections exist between ROM Monitor and the Cisco IOS XE software: the ROM Monitor environment variables and the configuration register.
The ROM Monitor environment variables define the location of the Cisco IOS XE software and describe how to load it. After the ROM Monitor has initialized the router, it uses the environment variables to locate and load the Cisco IOS XE software.
The configuration register is a software setting that controls how a card starts up. One of the primary uses of the configuration register is to control whether the router starts in ROM Monitor mode or Administration EXEC mode. The configuration register is set in either ROM Monitor mode or Administration EXEC mode as needed. Typically, you set the configuration register using the Cisco IOS XE software prompt when you need to use ROM Monitor mode. When the maintenance in ROM Monitor mode is complete, you change the configuration register so the router reboots with the Cisco IOS XE software.
Accessing ROM Monitor Mode with a Terminal Connection
When the router is in ROM Monitor mode, you can access the ROM Monitor software only from a terminal connected directly to the console port of the card. Because the Cisco IOS XE software (EXEC mode) is not operating, nonmanagement interfaces are not accessible. Basically, all Cisco IOS XE software resources are unavailable. The hardware is available, but no configuration exists to make use of the hardware.
Network Management Access and ROM Monitor Mode
It is important to remember that ROM Monitor mode is a router mode, not a mode within the Cisco IOS XE software. It is best to remember that ROM Monitor software and the Cisco IOS XE software are two separate programs that run on the same router. At any given time, the router runs only one of these programs, .
One area that can be confusing when using ROM Monitor and the Cisco IOS XE software is the area that defines the IP configuration for the Management Ethernet interface. Most users are comfortable with configuring the Management Ethernet interface in the Cisco IOS XE software. When the router is in ROM Monitor mode, however, the router does not run the Cisco IOS XE software, so that Management Ethernet interface configuration is not available.
When you want to access other devices, such as a TFTP server, while in ROM Monitor mode on the router, you must configure the ROM Monitor variables with IP access information.
The following sections describe how to enter the ROMMON mode, and contains the following sections:
To display the version of ROMmon running on a router, use the show rom-monitor command or the show platform command.
Table 5-1 summarizes the commands commonly used in ROM Monitor. For specific instructions on using these commands, refer to the relevant procedure in this document.
Table 5-2 describes the available help commands for ROM Monitor mode.
Note Commands are case-sensitive. You can halt any command by pressing Ctrl-C.
You can change the prompt in ROM Monitor mode by using the PS1= command as shown in the following example:
Changing the prompt is useful if you are working with multiple routers in ROM Monitor at the same time. This example specifies that the prompt should be “ISR4400 rommon ”, followed by the line number, and then followed by “ > “ by the line number.
To display the current configuration register setting, enter the confreg command without parameters as follows:
The configuration register setting is labeled Virtual Configuration Register . Enter the no command to avoid changing the configuration register setting.
The ROM Monitor environment variables define the attributes of the ROM Monitor. Environmental variables are entered like commands and are always followed by the equal sign (=). Environment variable settings are entered in capital letters, followed by a definition. For example:
Under normal operating conditions, you do not need to modify these variables. They are cleared or set only when you need to make changes to the way ROM Monitor operates.
This section includes the following topics:
Table 5-3 shows the main ROM Monitor environmental variables. For instructions on how to use these variables, see the relevant instructions in this document.
To display the current environment variable settings, enter the set command :
To exit ROM Monitor mode, you must change the configuration register and reset the router.
Use this procedure to upgrade the ROMmon on a router:
Step 1 (Optional) Run the show platform command or the show rom-monitor slot command on the router to see the current release numbers of ROMmon on the hardware. See the “Checking the Current ROMmon Version” section for information about interpreting the output of the command that you run.
Step 2 If the ROMmon image has not been copied onto the router, copy the PKG file that is made available as part of this ROMmon release onto the bootflash: or usb[0-1]: file system using the copy source-location destination-location command. For example, if you are upgrading to Release 15.2(1r)S, copy the isr4400-rommon-154-3r.S.pkg file.
Step 3 Run the dir file-system command to verify that the ROMmon file is copied into the specified directory.
Step 4 Run the upgrade rom-monitor filename location all command to begin the ROMmon image upgrade, where location is the path to the ROMmon file.
Step 5 Messages pertaining to the upgrade are displayed on the console. After the display of these messages stops and the router prompt is available, run the reload command to reload the router.
Step 6 If autoboot has not been enabled by using the config-register 0x2102 command, run the boot filesystem:/file-location command at the ROMmon prompt to boot the Cisco IOS XE image, where filesystem:/file-location is the path to the consolidated package file. The ROMmon upgrade is not permanent for any piece of hardware until the Cisco IOS XE image is booted.
Step 7 Run the enable command at the user prompt to enter the privileged EXEC mode after the boot is complete.
Step 8 Run the show platform command or the show rom-monitor slot command to verify whether the ROMmon has been upgraded.