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cat6k msfc2 boot procedure details?

  • From: Jochen Kaiser
  • Date: Fri Aug 15 05:43:59 2003

Good morning,

I try to understand the boot process of a msfc2 in cat6500 in
hybrid mode. After reading the appropriate docs at CCO and some
practise, I understand how to boot it and mostly (*sigh*) it 

Asking these detailed questions to ppl also administrating
cat6k revealed a deep lack of knowledge ;-(

Can anyone enlighten me/us?


I understand, that there are 4 mechanisms on the msfc2:

1. config register
2. BOOT variable (???)
3. BOOTLDR for helper image
4. 'boot system' statement in nvram config
I assume, that there are 3 image types:

1. ROM image 		-> loaded when all fails

2. a c6msfc2-boot image -> loaded when other image fails

   (that's what I've read, but I watched, that it is booted
    each time, also when a loadable normal image is reachable
    on bootflash)

3. a c6msfc2 		-> regular image 

Now we have different situations:

a) an image is defined in nvram config 'boot system'
   and the image is on the bootflash
   -> image loads

b) an image is defined but not on bootflash
   and there is an 'boot' image on bootflash
   -> boot-image boots

   my q:
   - is the position of the boot image of any relevance?
     I heard, that it is important, that it is the 1st 
     file on the bootflash. Is this right?
   - does this just happen, when the config register has
     the appropriate value of 0x2000 ?
   - what is the exact role of the 'BOOTLDR'-variable?

c) no image defined, config register 0x102
   and boot image is on bootflash
   -> ????

   my q:
   - What happens?

d) an image is defined in the 'BOOT'-variable
   -> ????
    my q: 
    - what is the sense of the boot-variable?
    - how is it set?

e) image is on ata-flash-disk and a boot image is on
   bootflash. image is defined via nvram 'boot system'

   -> since the appropriate image is not found,
      it boots the 'boot' image from bootflash, 
      reads the nvram config and sees the sup-disk0 and loads
      the real image as a replacement

   my q: 
   - is this correct? 


Especially I've a problem with setting the boot-variable (during
normal operation of a regular booted image).

router#sh boot
BOOT variable = sup-disk0:c6msfc2-jo3sv-mz.121-19.E.bin,1
CONFIG_FILE variable does not exist
BOOTLDR variable does not exist
Configuration register is 0x2102

tia & greetings,

Jochen Kaiser
Dipl. Inf. Jochen Kaiser, GPG 0x3C93A870, phone +49 9131 85-28681
Network Administration
Regionales Rechenzentrum Universitaet Erlangen-Nuernberg, Germany
Homepage and PublicKey: 

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