Solved: Tim,In simple terms, the

Tim Olson · ‎09-09-2014

I'm curious about boot loader images and if or why I should use one.

I've got a 6509 VSS setup running right now with no bootloader variable and no boot image.

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SHEC-VSS#sh boot
BOOT variable =
CONFIG_FILE variable =
BOOTLDR variable =
Configuration register is 0x2102

Standby BOOT variable =
Standby CONFIG_FILE variable =
Standby BOOTLDR variable =
Standby Configuration register is 0x2102

SWITCH-VSS#sh ver
Cisco IOS Software, s2t54 Software (s2t54-ADVIPSERVICESK9-M), Version 15.1(2)SY2, RELEASE SOFTWARE (fc3)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2014 by Cisco Systems, Inc.
Compiled Wed 26-Feb-14 16:03 by prod_rel_team

ROM: System Bootstrap, Version 12.2(50r)SYS3, RELEASE SOFTWARE (fc1)

SHEC-VSS uptime is 16 weeks, 3 days, 21 hours, 10 minutes
Uptime for this control processor is 16 weeks, 3 days, 21 hours, 10 minutes
System returned to ROM by power on
System restarted at 13:56:56 CDT Fri May 16 2014
System image file is "bootdisk:s2t54-advipservicesk9-mz.SPA.151-2.SY2.bin"
Last reload reason: power-on

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I'm about to set up a nearly identical VSS pair for another facility.

I just downloaded the latest SY3 version of IOS for the new pair, and there is a boot image available:

s2t54-boot-mz.SPA.151-2.SY3.bin

I just don't know why I would want or need that. Can anyone explain? I'm not a newbie by any means, but I just don't know why I'd need it. Right now, in the bootdisk: volume, I just have my IOS image: s2t54-advipservicesk9-mz.SPA.151-2.SY2.bin That was all that was in there before, but now that I'm building this new pair, I copied s2t54-advipservicesk9-mz.SPA.151-2.SY3.bin onto the same volume.

I understand that if I set a boot variable I can tell it to boot from one image or the other, but what does the BOOTLDR variable do for me. If I were to set the BOOTLDR variable to bootdisk:/s2t54-boot-mz.SPA.151-2.SY3.bin then what does that do for me? Right now, if I reboot, (until I added that 2nd image) it will just boot the only image in that directory with no issue.

What am I missing? Do I need to upgrade or use this boot image for anything?

Thanks for any tips you can provide!

Tim

InayathUlla Sharieff · ‎09-09-2014

Tim,

In simple terms, the bootldr file is the helper file to load the IOS.

The BOOTLDR environment variable specifies the Flash file system and filename that contains the boot loader image required to load system software.

The variable defines the primary Cisco IOS image that will load the final image from another source.

we need to set the BOOTLDR environment variable to specify the Flash device and filename of the boot loader image.

For Old version of IOS, there is a requirement of boot loader image to boot up the IOS image.

But for the latest version of IOS, no need for boot loader image.

Below are few things happen when the device boots:-

1. The router initially boots into ROMMON (this is your bootstrap code, which you can see in the show version command).

2. Then the router loads into the bootloader code (this is the bootloadr code, which you see in show version). This bootloader code is just an intermediate step between the ROMMON mode and the IOS mode.

3. The router then boots into the IOS mode from the bootloadr mode.

So if you do not mention the bootloadr specifically by giving the "boot bootloadr" command, the router will assume the bootloadr to be in bootflash of the device and try to boot it from there. If you mention the "boot bootloadr flash:...." command, then the router will look for the bootloadr in the flash (instead of the bootflash). Thats the only difference.

However, in both cases, if you have a valid IOS to boot into, then the router will come up without a problem, irrespective of the fact whether bootloadr image is in bootflash or flash.

HTH

REgards

Inayath

*Plz dont forget to rate if this info is helpfull.

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InayathUlla Sharieff · ‎09-09-2014