ios grade on 877

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Sep 8th, 2010
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Bit of a basic question but i need to get this done correctly

All i want to do is to upgrade the ios in an 877.

Not enough room for 2 ios so i will have to delete one

Cant find a guide for this and there appears to be no Boot command to tell the

router where to boot from in the flash

Do you just delete the old IOS and the the 877 will automatically boot from the

only IOS there ?

Any help appreciated as i dont want to plough ahead and end in in ROMMON


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Brandon Lynch Wed, 09/08/2010 - 08:22
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Hey Steve,

Without enough room in the flash for 2 images and no other places to store it, you will need to delete the old image to make room for the new one.  With that, however, come some checks you should run to ensure the image is valid and doesn't get corrupted during the download to the router.  Once the image is loaded in the flash, you can run the following commands -

Router#verify :

Router# verify /md5 :

From the second output, you should receive the calculated MD5 hash for the image which should match up with what is shown on the Software Download Page for that specific image.  Once this is verified, the image should be clean and bootable.

The router should check the flash for the first available image to boot if no boot statement is specified.  However, it's good practice to always have a boot statement to make sure the router knows where to look.  It is best to configure the following -

Router(config)# boot system flash :

Router# wr mem

This ensures that the router has the correct path and image specified and saved in the configuration so that upon reload, it knows precisely what to look for.  There are ways to boot a specific image from ROMmon but this should save you some headaches.

Alternatively, there are sometimes ways to boot remotely from a TFTP server but I would advise proceeding with the flash method as it is generally more reliable.  Hope this helps.


stephenswitzer Wed, 09/08/2010 - 08:54
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Thanks Brandon

Sadly no boot command on the 877 that i can find.

After checking verifying i guess i just reload and hope it picks up the only IOS there ?

Is that what it does ?


Brandon Lynch Wed, 09/08/2010 - 09:04
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What code are you running right now?  Can you send me the output of 'show version' along with the following -

Router(config)# boot ?

Router(config)# boot system ?

The router should pick up the correct IOS upon reload even without a boot statement but you should have the option to set it.  I'd like to check the outputs above to see what the router is reporting.


stephenswitzer Wed, 09/08/2010 - 09:42
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Brandon Lynch Wed, 09/08/2010 - 10:55
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That's right.  You will need to set up a boot statement to point to the correct image as I mentioned in my previous post -

Router(config)# boot statement flash :

Once this is configured, be sure to save the configuration and it should now show up in the running/startup config.  This ensures that the router knows exactly what to look for when booting up.


Scott Cannon Thu, 09/09/2010 - 22:14
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Hi Stephen,

I'll tell you how I do this when faced with limited flash.

1. I download the IOS and store it on a TFTP server (that the routers your trying to update can reach)

2. Boot the router

3. Delete the flash with erase flash: (your system may freeze up during this process, just grab a coffee while you wait NB: If you loose power a this point the restore process can be a real chore)

4. Copy the new image to flash with copy tftp flash

Just reboot. As Brandon has stated the router will boot an IOS file in the root of flash without you needing to configure a boot statement.



Leo Laohoo Thu, 09/09/2010 - 23:02
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Does this mean i have to set up a boot command on the router ?

With only one IOS in your router, you don't need to this.


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