Cisco 3725 Hardware Installation Guide - Page 103

Configuration Register

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Configuration Register C A P P E N D I X This appendix describes the factory default settings of the configuration register, and procedures for changing those settings. This appendix includes the following sections: • Configuration Register Settings, page C-1 • Changing Configuration Register Settings, page C-2 • Configuring the Boot Field, page C-3 • Enabling Booting from CompactFlash Memory, page C-5 Configuration Register Settings The router has a 16-bit configuration register in NVRAM. You can use the configuration register to perform the following tasks: • Set and display the configuration register value. • Force the router into the ROM monitor (bootstrap program). • Select a boot source and default boot filename. • Enable or disable the Break function. • Control broadcast addresses. • Load operating software from ROM. Table C-1 describes each of the configuration register bits. Table C-1 Configuration Bit Meanings Bit Number 00-03 06 07 08 09 Hexadecimal Meaning 0x0000-0x000F Boot field. (See Table C-2.) 0x0040 Causes the system software to ignore the contents of NVRAM. 0x0080 OEM bit enabled. 0x0100 Break disabled. 0x0200 Causes the system to use the secondary bootstrap. This bit is typically not used (set to 0). OL-2180-08 Cisco 3700 Series Routers Hardware Installation Guide C-1

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C-1
Cisco 3700 Series Routers Hardware Installation Guide
OL-2180-08
APPENDIX
C
Configuration Register
This appendix describes the factory default settings of the configuration register, and procedures for
changing those settings.
This appendix includes the following sections:
•
Configuration Register Settings, page C-1
•
Changing Configuration Register Settings, page C-2
•
Configuring the Boot Field, page C-3
•
Enabling Booting from CompactFlash Memory, page C-5
Configuration Register Settings
The router has a 16-bit configuration register in NVRAM. You can use the configuration register to
perform the following tasks:
•
Set and display the configuration register value.
•
Force the router into the ROM monitor (bootstrap program).
•
Select a boot source and default boot filename.
•
Enable or disable the Break function.
•
Control broadcast addresses.
•
Load operating software from ROM.
Table C-1
describes each of the configuration register bits.
Table C-1
Configuration Bit Meanings
Bit
Number
Hexadecimal
Meaning
00–03
0x0000–0x000F
Boot field. (See
Table C-2
.)
06
0x0040
Causes the system software to ignore the contents of NVRAM.
07
0x0080
OEM bit enabled.
08
0x0100
Break disabled.
09
0x0200
Causes the system to use the secondary bootstrap. This bit is typically not
used (set to 0).