ROM Monitor Command Conventions

Following are ROM monitor command conventions:

Aliasing ROM Monitoring Commands

The ROM monitor supports command aliasing modeled on the aliasing function built into the Korn shell. The alias command is used to set and view aliased names. This allows the user to alias command names to a letter or word. Aliasing is often used to shorten command names or automatically invoke command options.

Aliases are stored in NVRAM and remain intact across periods of no power. These are some of the set aliases.

ROM Monitor Commands

Enter ? or help at the rommon 12 > prompt to display a list of available commands and options, as follows:

The commands are listed and described in alphabetical order. Note that the ROM monitor commands are case-sensitive.

For example:

boot [-xv] [devid] [imagename]

b—Boots the default system software from ROM.

b filename [host]—Boots using a network TFTP server. When a host is specified, either by name or IP address, the boot command will boot from that source.

b flash:—Boots the first file in Flash memory.

b device:—Boots the first file found in the Flash memory device. The Flash memory device specified can be either flash:, to boot the Cisco IOS software, or bootflash:, to boot the boot image in Flash memory.

b device:name—An extension of the above command, allows you to specify a particular filename in the Flash memory bank.

The configuration register resides in NVRAM. The configuration register is identical in operation to other Cisco access servers. Enter confreg for the menu-driven system, or enter the new value of the register in hexadecimal.

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Virtual Configuration Register

This section describes the Cisco AS5200 series virtual configuration register, the factory default settings, and the procedures for changing those settings.

The Cisco AS5200 series has a 16-bit virtual register, which is written into the nonvolatile random access memory (NVRAM). Use the processor configuration register information contained in this section to do the following:

Table A-1 lists the meaning of each of the virtual configuration memory bits.

Table A-1   Virtual Configuration Bit Meanings

Changing Configuration Register Settings

Some common reasons to modify the value of the virtual configuration register follow:

To change the configuration register while running the IOS software, follow these steps:

Step 2   At the privileged-level system prompt (router #), enter the command configure terminal. You will be prompted as shown in the following example:

Step 3   To set the contents of the configuration register, enter the config-register value configuration command where value is a hexadecimal number preceded by 0x (see Table A-3), as in the following:

(The virtual configuration register is stored in nonvolatile memory.)

Step 4   Exit the configuration mode by entering Ctrl-Z. The new value settings will be saved to memory; however, the new settings do not take effect until the system software is reloaded by rebooting the router.

Step 5   To display the configuration register value currently in effect and the value that will be used at the next reload, enter the show version EXEC command, and the value will be displayed on the last line of the screen display as in the following example:

Step 6   Reboot the router. The new value takes effect. Configuration register changes take effect only when the server restarts, for example, when you switch the power off and on or when you issue a reload command from the console.

Configuring the Boot Field

The lowest four bits of the processor configuration register (bits 3, 2, 1, and 0) form the boot field. (See Table A-2.)

Table A-2   Explanation of Boot Field (Configuration Register Bits 00-03)

The boot field specifies a number in binary. If you set the boot field value to 0, you must have console port access to boot the operating system manually. Boot the operating system by entering the b command at the bootstrap prompt as follows:

Definitions of the various command options follow:

For more information about the b [tftp] flash filename command, see the appropriate software

publications. If you set the boot field value to a value of 2 through F, and there is a valid system boot command stored in the configuration file, the router boots the system software as directed by that value. (See Table A-3.) If you set the boot field to any other bit pattern, the router uses the resulting number to form a default boot filename for netbooting.

If there are no boot commands in the configuration file, the router attempts to boot the first file in system Flash memory. If no file is found in system Flash memory, the router attempts to netboot a default file whose name is derived from the value of the boot field (for example: cisco2-4500). If the netboot attempt fails, the boot helper image in boot Flash will boot up.

If boot commands are in the configuration file, the router software processes each boot command in sequence until the process is successful or the end of the list is reached. If the end of the list is reached without a file being successfully booted, the router will retry the netboot commands up to six times unless the boot default ROM software if netboot fails bit (bit 13 of the virtual configuration register) is set. If bit 13 is set, the system boots the boot helper image found in boot Flash memory without any retries.

In the following example, the virtual configuration register is set to boot the router automatically from Flash memory and to ignore Break at the next reboot of the router:

The server creates a default boot filename as part of the automatic configuration processes. To form the boot filename, the server starts with cisco and links the octal equivalent of the boot field number, a dash, and the processor-type name. Table A-3 lists the default boot filenames or actions for the processor.

Table A-3   Default Boot Filenames

Bit 8 controls the console Break key. Setting bit 8 (the factory default) causes the processor to ignore the console Break key. Clearing bit 8 causes the processor to interpret Break as a command to force the system into the bootstrap monitor, halting normal operation. A Break can be sent in the first 60 seconds while the system reboots, regardless of the configuration settings.

Bit 10 controls the host portion of the Internet broadcast address. Setting bit 10 causes the processor to use all zeros; clearing bit 10 (the factory default) causes the processor to use all ones. Bit 10 interacts with bit 14, which controls the network and subnet portions of the broadcast address.

Table A-4 shows the combined effect of bits 10 and 14.

Table A-4   Configuration Register Settings for Broadcast Address Destination

Bit 13 determines the server response to a bootload failure. Setting bit 13 causes the server to load operating software from ROM after five unsuccessful attempts to load a boot file from the network. Clearing bit 13 causes the server to continue indefinitely to attempt loading a boot file from the network. By factory default, bit 13 is cleared to 0.

Bits 11 and 12 in the configuration register determine the baud rate of the console terminal. Table A-5 shows the bit settings for the four available baud rates. (The factory-set default baud rate is 9600.)

Table A-5   System Console Terminal Baud Rate Settings

Enabling Booting from Flash Memory

To enable booting from Flash memory, set bits 3, 2, 1, and 0 to a value between 2 through 15. To specify a filename to boot, enter the system software configuration command boot system flash filename in the configuration file.

To enter the configuration mode while in the system software image, enter the configure command at the enable prompt as in the example following:

To disable break and enable the boot system flash command, enter the config-register command with a value as follows:

If you set the configuration register value to 0x102, as in the example, it is not necessary to enter the boot system flash command unless there is more than one image in Flash.

Posted: Sun Jan 19 07:25:24 PST 2003
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