Configuring The Software Configuration Register - Cisco 4500M Software Manual

Chapter 3 Configuring the Switch for the First Time
Understanding the ROM Monitor
The ROM monitor (ROMMON) is invoked at switch bootup, reset, or when a fatal exception occurs. The
switch enters ROMMON mode if the switch does not find a valid software image, if the NVRAM
configuration is corrupted, or if the configuration register is set to enter ROMMON mode. From
ROMMON mode, you can manually load a software image from bootflash or a Flash disk, or you can
boot up from the management interface. ROMMON mode loads a primary image from which you can
configure a secondary image to boot up from a specified source either locally or through the network
using the BOOTLDR environment variable. This variable is described in the
page
You can also enter ROMMON mode by restarting the switch and then pressing Ctrl-C during the first
five seconds of startup. If you are connected through a terminal server, you can escape to the Telnet
prompt and enter the send break command to enter ROMMON mode.
Ctrl-C is always enabled for five seconds after you reboot the switch, regardless of whether the
Note
configuration-register setting has Ctrl-C disabled.
The ROM monitor has these features:
•
•
•
•

Configuring the Software Configuration Register

The switch uses a 16-bit software configuration register, which allows you to set specific system
parameters. Settings for the software configuration register are preconfigured in NVRAM.
Here are some reasons why you might want to change the software configuration register settings:
•
•
•
•
•
•
•
To avoid possibly halting the Catalyst 4500 series switch switch, remember that valid configuration
Caution
register settings might be combinations of settings and not just the individual settings listed in
For example, the factory default value of 0x2101 is a combination of settings.
Table 3-3
field.
OL-6696-01
3-24.
Power-on confidence test
Hardware initialization
Boot capability (manual bootup and autoboot)
File system (read-only while in ROMMON)
To select a boot source and default boot filename
To control broadcast addresses
To set the console terminal baud rate
To load operating software from Flash memory
To recover a lost password
To manually boot the system using the boot command at the bootstrap program prompt
To force an automatic bootup from the system bootstrap software (boot image) or from a default
system image in onboard Flash memory, and read any boot system commands that are stored in the
configuration file in NVRAM
lists the meaning of each of the software configuration memory bits.
Modifying the Supervisor Engine Startup Configuration
Software Configuration Guide—Release 12.2(25)EW
"Switch#" section on
Table 3-3.
Table 3-4 defines the boot
3-19