My notes about Configuration Register on Cisco Routers

This page on Cisco.com defines all details about "Configuration Register" on Cisco routers.
http://www.cisco.com/c/en/us/support/docs/routers/10000-series-routers/50421-config-register-use.html

The Purpose of the Configuration Register
The configuration register can be used to change router behavior in several ways, such as:

• how the router boots (into ROMmon, NetBoot)
• options while booting (ignore configuration, disable boot messages)
• console speed (baud rate for a terminal emulation session)

Configuration registers are indeed DIP switches on most of PC motherboard.

DIP-Switch as part of a PCB from 1976, by Rainglasz.
Captured on Wikipedia.

So the following table captured on above post should be renamed to "Position of DIP switch". The positions are numbered from 0 to 15. Totally there are 16 DIP switches.

Position of DIP switch Bit Number	Hex	Meaning
00-03	0x0000-0x000F	Boots Field Parameters: 0x0000 - Stays at the system bootstrap prompt. 0x0001 - Boots the first system image in onboard Flash memory (EPROM). 0x0002-0x000F- Specifies a default netboot filename. Enables boot system commands that override the default netboot filename.
06	0x0040	Ignore NVRAM contents
07	0x0080	Disable boot messages
08	0x0100	Break disabled
10	0x0400	IP broadcast with all zeros
5,11,12	0x0020, 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 Ignores NVRAM contents

Two most frequently used combinations are:

• All routers' factory default: "0x2102"
• Ignores NVRAM, or when we forget password to login and we want to do a password reset: "0x2142".

Configuration Register Setting	Router Behavior
0x102	Ignores break 9600 console baud
0x1202	1200 baud rate
0x2101	Boots into bootstrap Ignores break Boots into ROM if initial boot fails 9600 console baud rate
0x2102 (Factory Defauly)	Ignores break Boots into ROM if initial boot fails 9600 console baud rate default value for most platforms
0x2120	Boots into ROMmon 19200 console speed
0x2122	Ignores break Boots into ROM if initial boot fails 19200 console baud rate
0x2124	NetBoot Ignores break Boots into ROM if initial boot fails 19200 console speed
0x2142 (Ignores NVRAM, also for password reset)	Ignores break Boots into ROM if initial boot fails 9600 console baud rate Ignores the contents of Non-Volatile RAM (NVRAM) (ignores configuration)
0x2902	Ignores break Boots into ROM if initial boot fails 4800 console baud rate
0x2922	Ignores break Boots into ROM if initial boot fails 38400 console baud rate
0x3122	Ignores break Boots into ROM if initial boot fails 57600 console baud rate
0x3902	Ignores break Boots into ROM if initial boot fails 2400 console baud rate
0x3922	Ignores break Boots into ROM if initial boot fails 115200 console baud rate

Cheers!