Easy Question: managing boot images on a router?

Unanswered Question
Jul 30th, 2007

Is there a easy way to manage which IOS a router will try to boot first and then if it fails boot to the 2nd image?

Case in point. I upgraded a 1811 router with a newer image. I want to tell the router to use the new image as the primary and reboot, then if it crashes or fails to load that primary image, reboot and load up the second old image that does work.

Normally I would use:

boot system flash:filename.bin

however as far as I have seen in the my experience the router will bootup whatever IOS image it sees first on the flash drive, then it will read the starting-config file and see that I am pointing at a different IOS to boot off of. At which point the router then loads the new IOS.

All of this wastes time as I have to wait for the 1st image to load to get the starting-config read before it does the boot system flash command.

I know I saw on 3500 switches where this isn't the case. Is there a trick for force it on a router to do this? Or am I just crazy and looking at this wrong?

I have this problem too.
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sundar.palaniappan Mon, 07/30/2007 - 11:36

The router sequentially processes the 'boot system commands' till it can successfully boot with a valid IOS image if the configuration register is set correct. It would only attempt to boot from the first IOS image on the flash if it can't successfully boot from any of the images that's specified in the 'boot system' command. I am just wondering whether you are talking about the 'bootstrap image' that the router boots first before it can start reading the boot variables configured. The router has to load the bootstrap image (small image) before it can read the boot variables like config register, boot system commands etc.

HTH

Sundar

mkmead Mon, 07/30/2007 - 11:48

Its been my experience that the order I see when I boot the router is:

bootstrap = which is the small ios image to get the router started.

then it searches the flash for the first IOS it sees and loads that up

then it loads up the starting-config file. it reads it and sees the boot system command

if the boot system command says boot another image it then stops and starts booting up that flash.

This entire process can be see with the ################## going across the screen as it boots up.

each ###### is the image loading.

sundar.palaniappan Mon, 07/30/2007 - 12:22

After it decompresses the bootstrap image the router should be able to read the 'boot system' commands and attempt to boot from the image in the top down order if multiple boot system commands are configured. Can you post the console output of where it shows loading the first image on the flash card?

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