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Appendix C Configuration Register
Changing Configuration Register Settings
Table
Bit |
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Number | Hexadecimal | Meaning |
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Boot field. (See Table | ||
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06 | 0x0040 | Causes the system software to ignore the contents of |
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| NVRAM. |
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07 | 0x0080 | OEM bit enabled. |
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08 | 0x0100 | Break disabled. |
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09 | 0x0200 | Causes the system to use the secondary bootstrap. |
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| This is typically not used (set to 0). |
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10 | 0x0400 | IP broadcast with all zeros. |
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5, 11, 12 | 0x0020, | Console line speed. |
| 0x0800, 0x1000 |
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13 | 0x2000 | Boots default ROM software if the network boot fails. |
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14 | 0x4000 | IP broadcasts do not have net numbers. |
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15 | 0x8000 | Enables diagnostic messages and ignores the contents |
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| of NVRAM. |
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Changing Configuration Register Settings
You might want to modify the value in the configuration register to perform the following tasks:
•Recover a lost password
•Change the console data rate
•Enable or disable the Break function
•Manually boot the operating system using the b command at the ROM monitor prompt
•Force the router to automatically boot its system image in Flash memory, or boot in accordance with any boot system commands stored in the router’s configuration file in NVRAM
You can change the configuration register from either the ROM monitor or the operating system software. To change the configuration register from the ROM monitor, see the “Configuration Register Commands” section on page
Step 1 Connect a console terminal to the console port of the router as described in the “Connecting to the
Console Port” section on page
Note If you have a terminal with a
For information about cable pinouts, refer to the online document Cisco Modular Access Router Cable Specifications. This document is available online and on the Cisco Documentation
Cisco 3600 Series Routers Hardware Installation Guide
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