
Chapter 3 Initial Configuration
About the Software Configuration Register
•Enable booting from a TFTP server
•Recover a lost password
•Boot the system manually using the boot command at the bootstrap program prompt.
•Force the system to boot automatically from the system bootstrap software (boot image) or from its default system image in onboard Flash memory, using any boot system commands stored in the startup configuration file in NVRAM
Software Configuration Register Settings
Table 3-4 describes each of the software configuration register bits.
Caution To avoid confusion and possibly halting the system, remember that valid configuration register settings might be combinations of settings and not just the individual settings listed in Table
Table
Bit Number | Hexadecimal | Description |
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00 to 03 | 0x0000 to 0x000F | Controls the system boot behavior (also known as the boot field) |
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06 | 0x0040 | Causes system software to ignore NVRAM contents |
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07 | 0x0080 | Enables the OEM bit |
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08 | 0x0100 | Disables the break function |
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09 | 0x0200 | Uses secondary bootstrap during system boot |
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10 | 0x0400 | Uses an IP broadcast with all zeros |
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11 to 12 | 0x0800 to 0x1000 | Sets the console line speed (default is 9600 baud) |
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13 | 0x2000 | Boots the default Flash software if network boot fails |
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14 | 0x4000 | Uses IP broadcasts without network numbers |
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15 | 0x8000 | Enables diagnostic messages and ignores the NVRAM contents |
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Bit 8 controls the console break function. Setting bit 8 (the factory default) causes the system to ignore the console break key. Clearing bit 8 causes the system to use the break key or break signal as a command to force the system into the bootstrap monitor (ROMMON), thereby halting normal operation.
Regardless of the setting of the break enable bit, a break causes a return to the ROMMON during the first few seconds (approximately five seconds) of booting.
Bit 9 controls the secondary bootstrap program function. Setting bit 9 causes the system to use the secondary bootstrap. Clearing bit 9 (the factory default) causes the system to ignore the secondary bootstrap. The secondary bootstrap program is used for system debugging and diagnostics.
Bit 10 controls the host portion of the IP broadcast address. Setting bit 10 causes the system to use all zeros. Clearing bit 10 (the factory default) causes the system to use all ones. Bit 10 interacts with bit 14, which controls the network and subnet portions of the IP broadcast address.
Table
| Cisco ONS 15530 Configuration Guide and Command Reference |