Table 31: Configuration Register Bit Descriptions
Meaning
Hexadecimal
BitNumber
Boot field. The boot field setting
determines whether the router loads
an operating system and where it
obtains the system image.
See the table "Boot Field
Configuration Register Bit
Descriptions" for details.
0x0000
–
0x000F
00
–
03
Causes the system software to
ignore the contents of NVRAM.
This can be used for password
recovery.
0x0040
06
The next table describes the boot field, which is the lowest four bits of the configuration register (bits 3, 2, 1,
and 0). The boot field setting determines whether the router loads an operating system.
Table 32: Boot Field Configuration Register Bit Descriptions
Meaning
Boot Field(Bits 3, 2, 1, and 0)
At the next power cycle or reload, the router boots to
the GRUB (bootstrap program).
In GRUB mode, you must manually boot the system
image or any other image by using the
boot
command.
0000
(0x0)
At the next power cycle or reload, the router
sequentially processes each
boot system
command
in global configuration mode that is stored in the
configuration file until the system boots successfully.
If no
boot system
commands are stored in the
configuration file, or if executing those commands is
unsuccessful, then the router attempts to boot the first
image file in flash memory.
0001 - 1111
(0x01 - 0x0F)
Use the 0x000 setting to configure the Cisco CSR 1000v to automatically enter GRUB mode when the
router boots.
Note
Cisco CSR 1000v Series Cloud Services Router Software Configuration Guide
222
Accessing and Using GRUB Mode
About GRUB Mode and the Configuration Register
