Difference between Disk:0 and Sup-bootflash

Horacio Gutierrez · ‎02-12-2014

Hello,

Can anyone tell me the difference between Disk:0 and Sup-bootflash. Where does the IOS boot from by default Disk:0 or Sup-bootflash. Can you configure 6509 Switch to boot the IOS from whaterver flash you want Disk:0 or Sup-bootflash?

Any Suggestions.

Thanks,

Ankur Arora · ‎02-12-2014

Hi Horacia,

The 6500 sup has a MSFC. The MSFC has a SP(switch processor) and RP(Route Processor). Both SP and RP have their own bootflash.

Our switch always boots from the SP and control is later passed to RP. And SP's bootflash is know as sup-bootflash.

So in order to boot a switch you should have the IOS image in the Sup-bootflash.

When you expand the Sup-bootflash, using a compact flash it is known as Sup-bootdisk, so you will boot the IOS using Sup-bootdisk.

Apart from these you can also boot your switch using an external flash card. Copy the IOS on the flash card from the PC and insert it in the SUP, so now when you boot the switch with the external flash card you are booting the switch from disk0.

So,

Sup-bootflash - bootflash of SP, from where the switch boots normally

Sup-bootdisk - expanded sup-bootflash (If you have a small size sup-bootflash you can increase its size by using a compact flash)

Disk0 - External Flashcard.

Thanks

Ankur

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Nameless-IT · ‎04-19-2019

Very Informative.Thank you.

Joseph W. Doherty · ‎02-13-2014

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Posting

Disk:0 (and Disk:1, on the sups that support it) is an accessible CF slot. Sup-bootflash is an internal flash for the SP. With native mode, it's not used. Bootflash is an internal flash used by the RP.

Default booting, usually uses the internal flash, on many of the later native IOSs, this can be overridden by IOS boot statements.

Older sup720s internal bootflash isn't large enough for the later IOS images so you're forced to boot from the external flash. (I work with quite a few of these. Often we keep an older IOS image on the internal bootflash so if someone pulls the CF, we have something to bring a sup720 on, although it may not recognize later line cards.)

Later sup720s have had their internal flash upgraded (to use an CF). The larger internal flash has been renamed to bootflash. BTW, there's also an upgrade kit to replace the older internal RP bootflash with a CF.

Besides the boot commands in an IOS image, the config-register also controls booting. If a sup720 just boots into ROMMOM, you can select different media/IOS images to boot from. Also BTW, there's different versions of the ROMMOM, which have some impact on how a sup720 can boot its IOS.

Horacio Gutierrez · ‎02-13-2014

Can I have the sup720 load from the internal flash ios but if the internal flash can it automatically failover the external cf flash or do u have to manually configure to boot from external flash if sup flash fails to load ios. If its possible to failover between flash what is the commands from for this?

Ankur Arora · ‎02-13-2014

Horacio,

Yes you can do that. Just issue two different boot variables, one for the internal flash and one for the external disk0.

Do the config will be like:

(config)#boot system flash sup-bootflash:ios image

(config)#boot system flash disk0:ios image

Before doing this just make sure you have the correct IOS image in the sup-bootflash and the disk0.

Thanks

Ankur

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Joseph W. Doherty · ‎02-13-2014

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The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

As Ankur notes, you just have consecutive boot command statements. However, from my experience, I don't recall sup-bootflash will work, at least with later IOS versions. Believe you'll want just bootflash or bootdisk.

BTW, you can leave the IOS image name off the command, and then it will use the first (or only) valid IOS image on that flash.

You can also, if desired, have more than one image on a flash. Anytime the boot command doesn't "work" it tries the next boot command. (Once it finds a valid image, it will boot that image.)

Something I like to do is (on a sup 720):

boot system flash disk1:

boot system flash disk0:

boot system flash bootdisk:

Then you can control boot image by what's loaded in the various flashes.

Ankur Arora · ‎02-13-2014

Joseph,

If you don't have the expansion compact flash on the switch the sup-bootflash should work. And if you have the expansion flash, then bootdisk will work. The reason sup-bootflash doesn't work on some later ios/sups is that Cisco started shipping those Sups with an expansion compact flash, so bootdisk works there. Like the Sup 2t, where the Sup is being shipped with a default compact flash, hence we have the bootdisk over there.

Thanks

Ankur

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Joseph W. Doherty · ‎02-13-2014

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

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In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

Ankur, about a year ago, I did quite a lot of testing on booting a 6500 with a sup720B.

I could "see" sup-bootflash (SP) and bootflash (RP) (64 MB?), but I was unable to get it to boot a native IOS from sup-bootflash. Booted from bootflash no problem. (Have other later/upgraded sup720s with 1 GB bootdisk, NP booting from their bootdisk either.)

With either bootflash or bootdisk also no problem booting from disk0: or disk1:. Also, a non-present CF in either (with boot string reference) didn't cause any issues, beyond, of course, it won't find an IOS on a non-existent flash.

Again, this was on a sup720, using SXF and SXI, the latter needing more than 64 MB flash. Cannot comment on sup2s, retired the last of ours a couple of years ago.