Need to upgrade image remotely on 2811..not enough space on flash card

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Nov 19th, 2008
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How can i upgrade the image (remotely) on my 2811 router?..the compact flash does not have enough room for 2 images..Can i delete the existing, tftp the new one & reload without losing the startup config file?...If so, how?


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Joseph W. Doherty Wed, 11/19/2008 - 10:24
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If the flash is formatted with the DOS like format, you might be able to just delete the current IOS image to free sufficient space to load the new image. (More space could be freed with additional flash file deletions.)

You can erase all the flash by formatting it, this should not erase the startup config which is usually written to NVRAM not flash.

Do realize if there is no valid IOS on the router, and for any reason it reboots, it will drop into rommon.

If you have physical access to the router, you can also use some USB devices to contain and even boot an IOS. Provides another way to have a backup/spare IOS available to the router. (USB IOS booting might require updating the ROM - can be done with TFTP on a 2811.)

Richard Burts Wed, 11/19/2008 - 12:51
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Your main concern seems to be whether erasing files in flash would impact your startup config. Joesph has given the correct answer that erasing (or even formatting) flash should not impact your startup config.

Joseph has also identified the main risk when you have to do a remote upgrade and there is not enough room in flash for 2 images: from the time that you erase the current image to the time that the new image is successfully copied into flash you are vulnerable. If the router reboots for some reason then there is no valid image to boot and it winds up in rommon.

You can erase the current image without impacting the running router. It can run just fine with no image in flash. The issue is what happens if something causes it to boot. In the situation that you describe I believe that you have no choice but to take that chance. It will probably work fine, but there is a risk that you should recognize.



Joseph W. Doherty Wed, 11/19/2008 - 13:35
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Anyone on-site with physical access to the router that you trust to insert a USB stick? If so, mail one there and insert it before you attempt to upgrade the IOS.

You can also pre-load the USB before sending it. And/or you can obtain, and send, another CF (which could also be larger to allow space for multiple images).

As Rick notes, remote flashes usually don't fail, but its nice to be able to preclude a problem by usage of a USB or CF card.


Without checking, don't recall whether USB and/or CF can be inserted/removed while router in operation.

graemeporter Sun, 11/23/2008 - 08:37
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Don't know about CF, but USB definitely can be inserted and removed during operation, no problem.

I've used USB sticks to upgrade 18xx, 28xx and 38xx several times, and have also performed upgrade by snail-mail that way as well (put the new image on the USB stick and mail it to someone with physical access to the device).

Kind regards



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