confreg parameters

[bninnemann]

I referenced my confreg examples from

http://www.cisco.com/en/US/products/hw/routers/ps133/products_tech_note09186a008022493f.shtml

My question is, why is 0x2102 the default if you can easily use 0x3922 instead?

The benefit being that your console serial speed is 12 times faster.

Is there more to the confreg values than is written in the guide?

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	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 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

If the value you have for the configuration register is not in  the table, then determine which bits are set in order to compute the  value:

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

[darren.g · Accepted solution]

Benjamin Ninnemann wrote:
I referenced my confreg examples from
http://www.cisco.com/en/US/products/hw/routers/ps133/products_tech_note09186a008022493f.shtml
My question is, why is 0x2102 the default if you can easily use 0x3922 instead?
The benefit being that your console serial speed is 12 times faster.

Basically, it's backward compatible from the days when 9600 baud was about all you could push through a serial port for console access.

Yes, you *can* set it higher - but 9600 is a known default, and the first thing any experienced engineer will try if they need console access because they know it's likely to be right in 99.99% of cases.

As for the rest - well, Cisco may have some hidden stuff they don't want us outsiders to know - but who is to tell?

Cheers.