Config reg values

liven

Ok I know about

0x2102 and 0x2142


But i don't understand all the other values. What i mean is I don't see how they break down in hex...

Can someone explain this for me so I can start practicing it?

networker050184

Check this out http://www.cisco.com/en/US/products/hw/routers/ps133/products_tech_note09186a008022493f.shtml which is on my favorites. It explains it all pretty well. Hope it helps.

liven

networker050184 wrote:

Check this out http://www.cisco.com/en/US/products/hw/routers/ps133/products_tech_note09186a008022493f.shtml which is on my favorites. It explains it all pretty well. Hope it helps.

ya that is definately good.


I was just hoping for a method to try to remember all the different values...

I really only use the 2 most common ones. Never needed any of the rest....

dtlokee

You should know the different boot field values (the last number) ie:

0x2100 will boot to rommon
0x2101 will boot to the mini IOS (helper IOS, the promt will say router(boot))
0x2102 will look to config file for how to boot (or from flash)

now changing the value of the 7th bit (in the second to last number) to 1 will ignore NVRAM

0x2142 will look to the config file to see how to boot (or flash) and will ignore the startup-config file.

APA

This is what I go by....

any thing that is 0x____0 =boots into ROMMON (eg 0x2120)

anything that is 0x_____1 ==boots from ROM(0x2101 is bootstrap as dtlokee mentioned and 0x2141 = boots from ROM and ignores NVRAM config)

anything that is 0x_____2 = follows the boot configuration and reads from NVRAM (eg 0x2102)

0x2142 = password recovery (follows boot configuration and ignores NVRAM)


*****Remember default path for booting IOS image = FLASH ---> TFTP ---> ROM*****

networker050184

I don't memorize any but the common ones either. I don't think you need to know them all for the exam, but know the basics that A.P.A pointed out.

APA

I'll just add that you shouldn't need to memorize absolutely every one.....

Just make sure you know what the last number in the hex value is indicating and you should be able to work out what is happening from there....


Ensure you can spit out relatively quickly what 0x2102 and 0x2142 mean though!!! :P

liven

Thanks all.

I pretty much have the things you guys said committed to memory.

I mean I have used 2102 and 2142 so many times...

I just saw a list of about 16 other values... I was thinking this test was starting to get out of hand....

Thanks again yall

liven

dtlokee wrote:

You should know the different boot field values (the last number) ie:

0x2100 will boot to rommon
0x2101 will boot to the mini IOS (helper IOS, the promt will say router(boot))
0x2102 will look to config file for how to boot (or from flash)

now changing the value of the 7th bit (in the second to last number) to 1 will ignore NVRAM

0x2142 will look to the config file to see how to boot (or flash) and will ignore the startup-config file.

The 2101 the mini ios is in ROM correct?

APA

yep..... You'll see it referred to as 'bootstrap' sometimes as well