I recently purchased a Cisco 4948 for use in my homelab to start learning about cisco gear. I was able to get it up and running without many issues, had it all configured but as happens in a homelab, swapping some gear around I powered down the device and upon reboot my settings were gone. So I reconfigured and power cycled it to test and it did it again.

After some more reading I figured out it had to do with the configuration register set to 0x2141 which ignores startup config. So I set it to 0x2102 which I understand is the correct setting to load the startup-config but it now enters 'rommon'. I am saving my config, and can confirm it is saved as if I enter 'boot' in rommon it will boot up with all my settings. Is 0x2102 the correct register to load my settings? Or could anything else be causing this?

I am a complete cisco noob, I have been reading a lot but maybe I am missing something obvious to some with actual experience. I appreciate any help or direction you can offer.

2 Answers 2


Check your configuration for a boot system command. If one exist, double check the filesystem, path and filename are correct. You could copy the full filesystem and filename from your command and then type dir followed by filesystem:filename and see if it actually shows the file exists.

If the command is set incorrectly, delete it and then re-add with correct location. Alternatively, try deleteting the command altogether and booting.

Sometimes, the command doesn’t exist, but you may need it if the IOS is in the wrong location, in this case, add the command yourself

Here is an example of the command:

boot system flash bootflash:cat4500-entservicesk9-mz.122-53.SG2_2.bin

Make sure it matches your filesystem (bootflash in this case) and filename exactly. If you are using a path within the filesystem, make sure you include it.

  • Thank you, this fixed the issue. My config did not have the boot system command. When I added it as you suggested it works perfectly. Is there a way to tell what the default boot system it attempts to use when nothing is present in the config?
    – dmmackay
    Commented Jul 26, 2018 at 14:23
  • show bootvar is the command to check what image will be used on next boot, not sure if it shows you anything if nothing is set. IOS usually boots from the oldest (lowest file ID) image on the flash, but it looks like it is maybe trying a different filesystem by default. Are there any other filesystems, CF card for example? It may be expecting the image to be on a different filesystem.
    – user27899
    Commented Jul 26, 2018 at 14:33

You need to save router IOS file to flash memory generally do by copy iOS file from outside memory source and boot it from pindrive or TFT server. After that it will work normally as desired. I hope you have a iOS file and you know to copy and run the iOS file.

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