Modifying The Boot Field And Using The Boot Command - Cisco Catalyst 4500 series Administration Manual

Chapter 3 Configuring the Switch for the First Time
Table 3-3
Bit Number
00 to 03
04
05
06
07
08
09
10
11 to 12
13
14
1. The factory default value for the configuration register is 0x2101. This value is a combination of the following: binary bit 13,
2. OEM = original equipment manufacturer.
Table 3-4
Boot Field Meaning
00
01
02 to 0F

Modifying the Boot Field and Using the boot Command

The configuration register boot field determines whether the switch loads an operating system image
and, if so, where it obtains this system image. The following sections describe how to use and set the
configuration register boot field and the procedures you must perform to modify the configuration
register boot field. In ROMMON, to modify the configuration register and change boot settings, use the
the confreg command.
Bits 0 through 3 of the software configuration register contain the boot field.
The factory default configuration register setting for systems and spares is 0x2101. However, the
Note
recommended value is 0x0102.
OL-30933-01
Software Configuration Register Bits
1
Hexadecimal
0x0000 to 0x000F Boot field (see
0x0010
0x0020
0x0040
0x0080
0x0100
0x0200
0x0400
0x0800 to 0x1000 Bits one and zero of Console line speed (default is 9600 baud)
0x2000
0x4000
bit 8 = 0x0100 and binary bits 00 through 03 = 0x0001. See
Explanation of Boot Field (Configuration Register Bits 00 to 03)
Stays at the system bootstrap prompt (does not autoboot).
Boots the first file in onboard flash memory.
Autoboots using image(s) specified by the BOOT environment variable. If more than one
image is specified, the switch attempts to boot the first image specified in the BOOT
variable. As long as the switch can successfully boot from this image, the same image is
used on a reboot. If the switch fails to boot from the image specified in the BOOT variable,
the switch tries to boot from the next image listed in the BOOT variable. If the end of the
BOOT variable is reached without the switch booting successfully, the switch attempts the
boot from the beginning of the BOOT variable. The autoboot continues until the switch
successfully boots from one of the images specified in the BOOT variable.
Modifying the Supervisor Engine Startup Configuration
Meaning
Table 3-4)
Unused
Bit two of console line speed
Causes system software to ignore NVRAM contents
2
OEM bit enabled
Unused
Unused
IP broadcast with all zeros
Loads ROM monitor after netboot fails
IP broadcasts do not have network numbers
Table 3-4.
Software Configuration Guide—Release IOS XE 3.6.0E and IOS 15.2(2)E
3-27