Cisco 2800 Series Manual page 192

About the Configuration Register
Table 1
Table 1
Bit
Number
00–03
06
07
08
09
10
05, 11,
12
13
Changing the Configuration Register Settings
2
describes the configuration register bits.
Configuration Register Bit Descriptions
Hexadecimal Meaning
0x0000–0x000F Boot field. The boot field setting determines whether the router loads an
operating system and where it obtains the system image.
See Table 2
0x0040 Causes the system software to ignore the contents of NVRAM.
0x0080 Original Equipment Manufacturer (OEM) bit enabled.
0x0100 Controls the console Break key:
•
•
Break can always be sent in the first 60 seconds while the router is
rebooting, regardless of the configuration register settings.
0x0200 This bit controls the system boot:
•
•
This bit is typically not modified.
0x0400 Controls the host portion of the IP broadcast address:
•
•
Bit 10 interacts with bit 14, which controls the network and subnet
portions of the IP broadcast address. See
of bits 10 and 14.
0x0020, Controls the console line speed. See
0x0800, 0x1000 combinations and console line speeds.
Factory default is 9600 baud, where bits 5, 11, and 12 are all zero (clear).
Note
0x2000 Determines how the router responds to a network boot failure:
•
•
for details.
(Factory default) Setting bit 8 causes the processor to ignore the
console Break key.
Clearing bit 8 causes the processor to interpret Break as a command
to force the router into the ROM monitor mode, halting normal
operation.
Setting bit 9 causes the system to use the secondary bootstrap.
(Factory default) Clearing bit 9 causes the system to boot from flash
memory.
Setting bit 10 causes the processer to use all zeros.
(Factory default) Clearing bit 10 causes the processor to use all ones.
You cannot change the console line speed configuration register
bits from the Cisco IOS command-line interface (CLI). You can,
however, change these bits from the ROM monitor (see
the ROM Monitor"). Or, instead of changing the configuration
register settings, you can set the console line speed through other
Cisco IOS commands..
Setting bit 13 causes the router to boot the default ROM software
after 6 unsuccessful network boot attempts.
(Factory default) Clearing bit 13 causes the router to indefinitely
continue network boot attempts.
Table 3 for the combined effects
Table 4 for the eight available bit
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