Cisco 4500 Boots to Rommon Mode

Sometimes when powering up a Cisco 4500 it will boot into Rommon mode by default rather than launching the Cisco IOS operating system as it should.

You can get the switch to boot from within Rommon mode simply by entering the command 'boot' however ideally we need to ensure that this isn’t necessary every time the switch is restarted.

Once you’re back in Cisco IOS there is a few things you can check.

• Ensure your config register is set to 0x2102 which is ‘standard’ mode. The config register can be verified using the command 'show version'.

• Check that the boot variable is set correctly on the switch. You can see the boot variables with the command 'show bootvar' If nothing is listed after the parameter “BOOT variable =” then we need to tell the switch which IOS image it should be loading upon boot.

• Check what versions of IOS are already stored on the switches internal flash. Chances are there is already at least one image we can boot into. Use the command 'dir:bootflash' You should see an image of Cisco IOS available in the list of files stored in the boot flash. The name of the file will be along the lines of “cat4500e-universalk9.SPA.03.06.06.E.152-2.E6.bin”. Ensure the file contains ‘k9’ somewhere in the filename. If you boot an image which is not ‘k9’ then you won’t be able to use SSH on the switch.

• Tell the switch to boot the correct IOS image using the below command 'boot system flash bootflash:cat4500e-universalk9.SPA.03.06.06.E.152-2.E6.bin'

• Save the switches config 'copy start run' and then reboot it 'reload'. The switch should now boot into the correct IOS image without getting stuck in Rommon.