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bootflash and sup-bootflash in Cisco 6509 switch

bootflash and sup-bootflash in Cisco 6509 switch

In my production environment I went through a case where I noticed a behavior of Cisco 6509 switch in which there were bootflash and sup-bootflash where IOS images can be stored and then set the boot variable on either of these. In this switch there was an Image in Sup-bootflash and bootflash did not have an image. Then Boot variable was set to bootflash (which does not have image). What will happen when switch is rebooted?

Below is the test performed.

In this simulation I do not have image in bootflash but it is kept in sup-bootflash as shown below.

 Bootflash does not have image.

LAB-6509#sh bootflash:

No files on device

65536000 bytes available (0 bytes used)

Sup-bootflash does have an image- s72033-advipservicesk9_wan-mz.122-33.SXI8.bin

LAB-6509#sh sup-bootflash:

-#- –length– —–date/time—— path

1     33554432 Feb 26 2013 12:47:54 +00:00 sea_console.dat

2     73785828 Aug 29 2012 00:36:22 +00:00 s72033-ipservices_wan-mz.122-33.SXH8b.bin

3     33554432 Aug 29 2012 00:35:40 +00:00 sea_log.dat

4   116796260 Nov 22 2012 11:55:22 +00:00 s72033-advipservicesk9_wan-mz.122-33.SXI8.bin

5   107564076 Dec 6 2012 11:16:32 +00:00 s72033-adventerprisek9-mz.151-1.SY.bin

——–output truncated——————

4849664 bytes available (507224064 bytes used)

Now we have set the boot variable to bootflash instead of sup-bootflash as show below

System var is set to bootflash:s72033-advipservicesk9_wan-mz.122-33.SXI8.bin

LAB-6509#sh run | in system

boot system bootflash:s72033-advipservicesk9_wan-mz.122-33.SXI8.bin

spanning-tree extend system-id

LAB-6509#sh bootvar

BOOT variable = bootflash:s72033-advipservicesk9_wan-mz.122-33.SXI8.bin,12;

CONFIG_FILE variable does not exist

BOOTLDR variable does not exist

Configuration register is 0x2102


Standby not ready to show bootvar


After reload the switch, it is booted from sup-bootflash s72033-advipservicesk9_wan-mz.122-33.SXI8.bin as shown below


LAB-6509#sh version | in System

Copyright (c) 1986-2011 by Cisco Systems, Inc.

ROM: System Bootstrap, Version 12.2(17r)SX7, RELEASE SOFTWARE (fc1)

System returned to ROM by reload at 10:23:53 UTC Wed Jun 4 2014 (SP by reload)

System image file is “sup-bootflash:s72033-advipservicesk9_wan-mz.122-33.SXI8.bin”


When this switch was rebooted, it was rebooted from the sup-bootflash.

It means when switch boots up it looks at the bootflash (where boot variable was set) and if switch does not find any image on this, it checks in sup-bootflash if there is any image for booting the switch. In this case switch finds the image in sup-bootflash.


Deepak Sharma, CCIE#37340


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