C-2
Cisco 3700 Series Routers Hardware Installation Guide
OL-2180-08
Appendix C Configuration Register
Changing Configuration Register Settings
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 CompactFlash 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 either from the ROM monitor or from the operating system
software. To change the configuration register from the ROM monitor, see the
“Configuration Register”
section on page B-6
. To change the configuration register from the system software, perform the
following steps:
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 3-22
, using the blue RJ-45 to DB-9 console adapter cable.
Note
If you have a terminal with a DB-25 port, use an RJ-45 rollover cable and DB-25 adapter. The
RJ-45-to-DB-25 adapter (Cisco part number 29-0810-01) can be purchased from Cisco.
For information about cable pinouts, see the publication
Cisco Modular Access Router Cable
Specifications
on Cisco.com.
Step 2
Configure your terminal or terminal emulation software for 9600 bps (default), 8 data bits, no parity, and
2 stop bits.
Step 3
Power up the router.
Step 4
When asked if you would like to enter the initial dialog, answer
no
:
Would you like to enter the initial dialog? [yes]:
no
Your router is now in the normal operating mode.
10
0x0400
IP broadcast with all zeros.
5, 11, 12
0x0020,
0x0800, 0x1000
Console line speed.
13
0x2000
Boots default ROM software if the network boot fails.
14
0x4000
IP broadcasts do not have net numbers.
15
0x8000
Enables diagnostic messages and ignores the contents of NVRAM.
Table C-1
Configuration Bit Meanings (continued)
Bit
Number
Hexadecimal
Meaning
