Which Configuration Register Ignores Nvram?
Tabular array Of Contents
Modifying the Switch Boot Configuration
Understanding How the Switch Kicking Configuration Works
Understanding the Boot Process
Understanding the ROM Monitor
Understanding the Configuration Register
Understanding the Kick Environment Variable
Understanding the CONFIG_FILE Surroundings Variable
Default Switch Boot Configuration
Setting the Configuration Register
Setting the Kick Field in the Configuration Register
Setting CONFIG_FILE Recurrence
Setting the Switch to Ignore the NVRAM Configuration
Setting the BOOT Surround Variable
Setting the Kicking Environment Variable
Clearing the Boot Environment Variable Settings
Setting and Immigration the CONFIG_FILE Environment Variable
Setting the Variable
Immigration the Variable Settings
Displaying the Switch Boot Configuration
Modifying the Switch Kicking Configuration
This affiliate describes how to alter the switch boot configuration, including the Kick environment variable and the configuration register on the Goad enterprise LAN switches.
Note 
For consummate syntax and usage information for the commands used in this chapter, refer to the Command Reference—Goad 4000 Family, Catalyst 2948G, and Goad 2980G Switches.
This chapter consists of these major sections:
•Understanding How the Switch Kicking Configuration Works
•Default Switch Boot Configuration
•Setting the Configuration Annals
•Setting the BOOT Environment Variable
•Setting and Immigration the CONFIG_FILE Surroundings Variable
•Displaying the Switch Boot Configuration
Understanding How the Switch Kicking Configuration Works
These sections describe how the boot configuration works on the Catalyst 4000 family, 2948G, and 2980G switches:
•Understanding the Kicking Process
•Understanding the ROM Monitor
•Agreement the Configuration Register
•Understanding the BOOT Surroundings Variable
•Understanding the CONFIG_FILE Environment Variable
Understanding the Boot Process
The boot process involves two software images: ROM monitor and supervisor engine system code. When the switch is powered up or reset, the ROM-monitor code is executed. Depending on the nonvolatile RAM (NVRAM) configuration, the switch either stays in ROM-monitor mode or loads the supervisor engine system code.
Two user-configurable parameters determine how the switch boots: the configuration register and the Boot environment variable. The configuration register is described in the "Agreement the Configuration Register" section. The Kick environment variable is described in the "Understanding the BOOT Environment Variable" section.
Agreement the ROM Monitor
The ROM monitor code executes upon switch power-upwardly, reset, or when a fatal exception occurs. The organization enters ROM-monitor mode if the switch does non discover a valid organization epitome, if the NVRAM configuration is corrupted, or if the configuration register is set to enter ROM-monitor mode. From ROM-monitor manner, you lot can manually load a system image from Flash retention, from a network server file, or from bootflash.
Note For complete syntax and usage information for the ROM monitor commands, refer to the Command Reference—Goad 4000 Family, Catalyst 2948G, and Catalyst 2980G Switches.
You lot can enter ROM-monitor mode by restarting the switch and then pressing Ctrl-C during the starting time 5 seconds of startup.
The following functionality is congenital into the ROM monitor:
•Power-on confidence exam
•Hardware initialization
•Boot adequacy (allows manual boot and autoboot)
•Debug utility and crash analysis
•File system (the ROM monitor knows the simple file organization and supports the newly developed file arrangement through the dynamic linked file organisation library [MONLIB])
•Exception handling
Understanding the Configuration Register
The configuration register determines whether the switch loads an operating organisation image and where the organisation image is stored. The configuration register boot field determines if and how the ROM monitor loads a supervisor engine organisation image at startup. You can modify the kick field to force the switch to kick a particular system epitome at startup instead of using the default system image.
The lowest four bits (bits iii, 2, 1, and 0) of the 16-fleck configuration register form the boot field. The default kick field value is 0x10F. The possible configuration register boot field settings are as follows:
•When the boot field equals 0000, the switch does not load a system epitome. The switch enters ROM-monitor mode from which you can enter ROM-monitor commands to manually load a organisation image.
•When the boot field equals 0001, the switch loads the first valid organisation image institute in onboard Wink retentivity.
•When the boot field equals a value between 0010 and 1111, the switch loads the system prototype specified past boot organization commands in the NVRAM configuration. Information technology attempts to kicking the image in the lodge in which you entered the boot system commands. If information technology cannot kicking any epitome in the BOOT surround variable listing, the switch remains in ROM-monitor style. The exact booting sequence is defined by the ROM monitor.
The other bits in the configuration register function every bit follows when fix:
•Fleck five (0x0020): Enables CONFIG_FILE recurrence.
•Bit six (0x0040): Causes system software to clear NVRAM contents.
•Bit 7 (0x0080): Enables OEM bit (not used).
•Bit 8 (0x0100): Disables suspension.
•Scrap ix (0x0200): Uses secondary bootstrap (not used by the ROM monitor).
•Bit 10 (0x0400): Provides IP broadcast with all zeros (non used).
•$.25 11/12 (0x0800/0x1000): These bits are always set to 0/0 (9600 baud).
•Bit 13 (0x2000): Boots default Flash software if network kick fails (non used).
•Chip fourteen (0x4000): IP broadcasts practise not have network numbers (non used).
•Bit 15 (0x8000): Enables diagnostic letters and ignores NVRAM contents (non used).
Understanding the Kick Environment Variable
The BOOT environment variable specifies a list of image files on various devices from which the switch can boot at startup.
You can add several images to the Boot environment variable to provide a fail-condom kick configuration. If the kickoff file fails to boot the switch, subsequent images specified in the BOOT variable are tried until the switch boots or there are no additional images to endeavour to boot. If there is no valid image to kick, the organization enters ROM-monitor mode where you tin manually specify an image to boot.
The system stores and executes images in the club in which you added them to the Boot variable. If you want to alter the club in which images are tried at startup, you tin can either prepend and articulate images from the BOOT variable to attain the desired guild or you lot can clear the entire Boot surround variable then redefine the list in the desired order.
Understanding the CONFIG_FILE Environment Variable
In software release 5.2 and subsequently releases, you can use the CONFIG_FILE environs variable to specify a list of configuration files on various devices to use to configure the switch at startup. You can specify ane of the post-obit functions:
•Nonrecurring—When you add a listing of configuration files to the CONFIG_FILE environment variable, the side by side fourth dimension the switch is restarted, the system erases the configuration in NVRAM and uses the specified files to configure the switch. The CONFIG_FILE variable is cleared before the switch is configured. Nonrecurring is the default setting.
•Recurring—When you add together a listing of configuration files to the CONFIG_FILE surroundings variable, the list is stored indefinitely in NVRAM. Each time the switch is restarted, the organization erases the configuration in NVRAM and configures the switch using the configuration files specified. The CONFIG_FILE variable is not cleared.
Note Remember that the CONFIG_FILE variable tin be altered or its recurrence properties inverse by commands in the configuration files used to configure the switch at startup.
For information on specifying recurrence or nonrecurrence, see the "Setting CONFIG_FILE Recurrence" section.
When the switch boots upwardly, if any of the files specified in the CONFIG_FILE environment variable are valid configuration files, the configuration in NVRAM is erased and the system uses the specified configuration file to configure the switch. If multiple valid configuration files are specified, each configuration file is executed in the order in which information technology appears in the CONFIG_FILE environment variable.
If any specified file is not a valid configuration file, the entry is skipped and subsequent files are tried until in that location are no additional images specified. If no valid configuration file is specified, the organisation retains the concluding configuration stored in NVRAM.
Note For more than data well-nigh using configuration files, encounter "Working with Configuration Files."
Default Switch Kick Configuration
Table 29-one shows the default switch boot configuration.
| Feature | Default Configuration |
|---|---|
| Configuration register value | 0x10f |
| Kicking method | System boots from the paradigm specified in the BOOT environment variable |
| ROM monitor console port baud charge per unit | 9600 baudone |
| ignore-config parameter | Disabled |
| Kick environment variable | Empty |
| CONFIG_FILE environment variable | bootflash:switch.cfg |
| CONFIG_FILE recurrence configuration register parameter | Nonrecurring |
1 The ROM monitor console port baud charge per unit is always 9600 baud.
Setting the Configuration Annals
These sections draw how to modify the configuration register:
•Setting the Boot Field in the Configuration Annals
•Setting CONFIG_FILE Recurrence
•Setting the Switch to Ignore the NVRAM Configuration
Setting the Boot Field in the Configuration Register
Yous can determine the kicking method the switch volition use at the side by side startup past setting the boot field in the configuration annals. This command affects just the configuration register $.25 that control the kicking field and leaves the remaining bits unaltered.
The following boot methods are supported:
•ROM monitor—Use the rommon keyword to keep the switch in ROM-monitor mode at startup.
•Bootflash—Apply the bootflash keyword to cause the switch to boot from the start epitome stored in the onboard Flash.
•Arrangement—Use the organization keyword to boot from the image specified in the Kicking environment variable (the default).
Annotation Nosotros recommend that y'all utilize only the rommon and system options to the fix boot config-register kick control.
To ready the configuration register kicking field, perform this task in privileged mode:
| Task | Command |
|---|---|
| Specify the boot field in the configuration annals. | prepare kicking config-annals boot {rommon | bootflash | arrangement} [mod_num] |
This example shows how to force the switch to enter ROM-monitor mode at the next startup:
Panel> (enable) set boot config-register kicking rommon
Configuration register is 0x0
auto-config: not-recurring
Setting CONFIG_FILE Recurrence
By default, when you set the CONFIG_FILE surround variable, the listing of configuration files to employ at startup is retained just until the adjacent time the switch is restarted.
You can cause the organization software to retain the CONFIG_FILE environment variable settings indefinitely so that each time the switch is restarted, the specified configuration files are used to configure the switch.
This control affects but the configuration annals fleck that controls whether the CONFIG_FILE surround variable settings are recurring or nonrecurring. The remaining configuration register bits are unaltered.
Caution With the CONFIG_FILE environs variable set to recurring, the current configuration in NVRAM is erased each time the switch is restarted and the switch is configured using the specified configuration files. With the CONFIG_FILE environment variable fix to non-recurring, the current configuration in NVRAM is erased at the next restart and the switch is configured using the specified configuration files. The NVRAM configuration is retained after subsequent restarts (unless you once more fix the CONFIG_FILE variable).
To set the switch to retain the current CONFIG_FILE surroundings variable indefinitely, perform this task in privileged mode:
| Chore | Command |
|---|---|
| Ready the switch to retain the electric current CONFIG_FILE surround variable indefinitely. | set boot config-register auto-config {recurring | not-recurring} |
This example shows how to ready the switch to retain the current CONFIG_FILE variable indefinitely:
Console> (enable) fix boot config-register auto-config recurring
Configuration annals is 0x1820
Setting the Switch to Ignore the NVRAM Configuration
You can cause the system software to ignore the configuration information stored in NVRAM the next time the switch is restarted. This command affects only the configuration register bits that control whether the switch ignores the NVRAM configuration and leaves the remaining bits unaltered. This command only affects the next system restart.
Caution Enabling the ignore-config parameter is the same every bit entering the clear config all command; that is, it clears the entire configuration stored in NVRAM the side by side time the switch is restarted.
To set the switch to ignore the NVRAM configuration at the next startup, perform this task in privileged style:
| Chore | Command |
|---|---|
| Set the switch to ignore the contents of NVRAM at startup. | set boot config-register ignore-config enable |
This example shows how to set up the switch to ignore the NVRAM configuration at the next startup:
Console> (enable) ready boot config-annals ignore-config enable
Configuration register is 0x1860
Setting the BOOT Surround Variable
The next ii sections describe how to modify the Kick environment variable.
Setting the Boot Environment Variable
To ready the BOOT environment variable, perform this job in privileged mode:
| Task | Command |
|---|---|
| Specify a system prototype to add to the Boot environment variable. | set up boot arrangement flash device:[filename] [prepend] [mod_num] |
This case shows how to add organization images to the Boot environment variable:
Console> (enable) set boot system flash bootflash:cat4000.5-1-1.bin
BOOT variable = bootflash:cat4000.5-ane-i.bin,one;
Console> (enable) set kick organization wink bootflash:cat4000.iv-5-2.bin
Kick variable = bootflash:cat4000.5-one-1.bin,i;bootflash:cat4000.4-5-2.bin,1;
Console> (enable) set kick system wink bootflash:cat4000.6-one-ane.bin prepend
Kicking variable = bootflash:cat4000.6-1-1.bin,ane;bootflash:cat4000.5-i-1.bin,1;
bootflash:cat4000.four-5-2.bin,1;
Clearing the BOOT Environment Variable Settings
To clear entries from the BOOT environment variable, perform one of these tasks in privileged style:
| Task | Command |
|---|---|
| Clear a specific image from the BOOT environment variable. | clear boot system flash device:[filename] [mod_num] |
| Clear the entire Kick surround variable. | clear boot system all [mod_num] |
This instance shows how to articulate a specific entry from the Kick environment variable:
Console> (enable) clear boot system flash bootflash:cat4000.5-1-i.bin
Kick variable = bootflash:cat4000.5-ii-1.bin,1;bootflash:cat4000.four-5-2.bin,ane;
This instance shows how to clear the unabridged BOOT environment variable:
Panel> (enable) articulate kicking organization all
Setting and Clearing the CONFIG_FILE Surroundings Variable
The adjacent ii sections depict how to set and clear the CONFIG_FILE environment variable.
Note For more data about using configuration files, run into "Working with Configuration Files."
Setting the Variable
You lot tin can specify multiple configuration files with the set up boot motorcar-config command by separating them with a semicolon (;). Y'all must specify both the device name and the filename for each configuration file.
Note You cannot prepend or append configuration files to the CONFIG_FILE environment variable. Entering the set boot auto-config control erases any list of configuration files previously specified using the set up boot auto-config command.
To ready the CONFIG_FILE environment variable, perform this task in privileged mode (depending on your supervisor engine and switch type):
| Job | Command |
|---|---|
| Specify the list of configuration files to add together to the CONFIG_FILE environment variable. | set boot auto-config device:filename[; device:filename...] |
This case shows how to add a list of configuration files to the CONFIG_FILE surround variable:
Console> (enable) prepare boot auto-config bootflash:generic.cfg;bootflash:4003_1_noc.cfg
CONFIG_FILE variable = bootflash:generic.cfg;bootflash:4003_1_noc.cfg
WARNING: nvram configuration may be lost during next bootup,
and re-configured using the file(south) specified.
Clearing the Variable Settings
To clear the entries from the CONFIG_FILE environment variable, perform this task in privileged mode:
| Task | Command |
|---|---|
| Articulate the entries in the CONFIG_FILE environment variable. | clear kick auto-config |
This case shows how to clear the entries in the CONFIG_FILE environment variable:
Console> (enable) clear kick auto-config
Displaying the Switch Boot Configuration
To display the current configuration register, BOOT environment variable, and CONFIG_FILE environment variable settings, perform this job in privileged mode:
| Task | Command |
|---|---|
| Brandish the current configuration register, Kick environment variable, and CONFIG_FILE environment variable settings. | show boot [mod_num] |
This example shows how to display the current configuration register, Boot surroundings variable, and CONFIG_FILE environment variable settings:
Console> (enable) prove kicking
BOOT variable = bootflash:cat4000.5-ii-1.bin,1;
CONFIG_FILE variable = bootflash:generic.cfg;bootflash:4003_1_noc.cfg
Configuration register is 0x12f
boot: image specified by the boot system commands
Source: https://www.cisco.com/en/US/docs/switches/lan/catalyst4000/7.5/configuration/guide/boot_support_TSD_Island_of_Content_Chapter.html
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