APPENDIX
Cisco 4000 Series Virtual Configuration Register B-1
Cisco 4000 Series Virtual
Configuration Register
B
This appendix describes the Cisco 4000 series virtual configuration register, the factory default
settings, and the procedures for changing those settings.
Virtual Configuration Register Settings
The Cisco 4000 series has a 16-bit virtual register, which is written into the nonvolatile random
access memory (NVRAM). Use the processor configuration register information contained in this
appendix to do the following:
• Set and display the configuration register value.
• Force the system into the bootstrap program.
• Select a boot source and default boot filename.
• Enable or disable the Break function.
• Control broadcast addresses.
• Set the console terminal baud rate.
• Load operating software from ROM.
• Enable booting from a Trivial File Transfer Protocol (TFTP) server.
Table B-1 lists the meaning of each of the virtual configuration memory bits.
Table B-1 Virtual Configuration Bit Meanings
Bit No. Hex Meaning
00–03 0x0000–0x000F Boot field (see Table B-2)
06 0x0040 Causes system software to ignore nonvolatile memory contents
07 0x0080 OEM bit enabled
08 0x0100 Break disabled
10 0x0400 IP broadcast with all zeros
11–12 0x0800–0x1000 Console line speed
13 0x2000 Boots default ROM software if network boot fails
14 0x4000 IP broadcasts do not have net numbers
15 0x8000 Enables diagnostic messages and ignores NVRAM contents
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