ios flash and version Question

[nabdb]

When I do a show version command, it lists 2 different images. The IOS and the ROM:

Cisco IOS Software, C1700 Software (C1700-Y-M), Version 12.4(5c), RELEASE SOFTWA
RE (fc3)

ROM: System Bootstrap, Version 12.1(5r)T1, RELEASE SOFTWARE (fc1)
ROM: C1700 Software (C1700-ADVSECURITYK9-M), Version 12.3(9), RELEASE SOFTWARE (fc2)

What is this ROM image? I thought you only need one IOS image. Here is flash:

System flash directory:
File Length Name/status
1 9375208 c1700-advsecurityk9-mz.123-9.bin
2 8004076 c1700-y-mz.124-5c.bin

Is it safe to delete the 12.3(9) to make room? I dont want to break n e thing come reload time.

 

[spidey07]

You should also see your system image filename - that tells you exactly what file it loaded to run. "show boot" also to see what you told the router to load.

The ROM image is the low level image that gets the router boot process going. This is also where the very basic "ROM Monitor" code is. rommon is very low level and just has enough functionality to get an image onto the router.

You can delete any file you like. Just make sure that the router has at least one good image, and you have specified this image with the "boot system flash:<filename>" command.

 

[nabdb]

i understand all of the above, but say i delete 12.3(9) and 12.4(5c), and i put on 12.4(8a)

when i reload, is the ROM software going to change to 12.4(8a) as well, or will it stay 12.3(9)? if it changes to 12.4(8a), why is it not at 12.4(5c) now?

if it doesnt change, how can it load 12.3(9) into rom when the bin file is no longer present. unless since its rom and not flash, it will never change. in that case, how come the rom file is corresponding to an image file in flash.

im just confused on where its getting the 12.3(9) in rom...

 

[spidey07]

It's stored in rom (or flashable rom depending on the router model) on the router itself. You don't need to worry about it at all.

 

[cmetz]

spidey07, my understanding that could be wrong is that there's three pieces:

rommon - the monitor you get from hitting break - in ROM or flash you can't touch

bootstrap image - a stripped version of IOS that knows how to read flash filesystems and the config boot block - depending on platform, in ROM, in flash you can't touch, or in flash you can touch (higher end boxen)

real image - full IOS, from flash you can touch

Hence the double-boot process, where you basically boot up a small copy of IOS just to be the boot loader for the real IOS image.

nabdb, in a 1700, you can fry everything in flash and should be able to boot the ROM IOS image and load in an image from there. This is not recommended, though.

Remember to update your 'boot system flash' line.

 

[spidey07]

I could very well be off base.

Only rarely have I had to change the bootstrap image in even the biggest routers. Mainly to recognize bigger file systems/or different storage devices from which to boot. Don't really know though.

I guess ROM does really mean "read only". 😉

And to your point...if you really need to you can transfer an IOS image using a serial connection using ROMMON. You can get a dead router back no matter what. It's not fun, and it's not fast. But you can do it.

This makes me thing that ROMMON is truely burned in. Bootstrap is just slimmed down to tell it how to deal with "where the hell is my software, dammit!!!! I was to understand there is software to load! WTF is wrong with you! Where's my damn software!!!!! I need to boot before I can do a goddangged thing!"

😉