how to boot Cisco IOS from USB

Cisco 2811 with USB boot and v15 IOS

:: Prerequisites ::

So assume you are having Cisco 2811 router with USB port(s). Also realized that you don't have enough space on Flash Memory? So let's boot from USB Flash then :)
You need CSO account to download a bootstrap with USBBoot support from https://www.cisco.com

Bootstrap Filename:
C2800NM_RM2.srec.124-13r.T or newest C2800NM_RM2.srec.124-13r.T11

 :: HOW-TO Boot Cisco IOS from USB flash disk ::

Insert USB (formatted as FAT32!) to your C2811 and check logs if router read yours USB flashdisk. If yes, great!

You can format your USB and when done stick it into your PC slot.

router#format usbflash0:

Copy the boostrap and Eject / Disconnect the USB flashdisk - no need to set-up boot flag.

Connect your freshly formatted USB with new bootstrap to Cisco router again.

:: CMDS ::

Commands needed: type enable to get router# privileged mode
sh file system

!

cd usbflash0:

!

pwd

!

dir

!

copy usbflash0:C2800NM_RM2.srec.124-13r.T11 flash:

!

dir flash:

! --verify if bootstrap is there

upgrade rom-monitor file C2800NM_RM2.srec.124-13r.T11

!           --router will reload here!

en

!
conf t

!

boot system usbflash0:c2800nm-adventerprisek9_ivs-mz.151-4.M10.bin

!

do wr

!

end

!

reload

And we are booting v. 15 Cisco IOS from USB flash now! :) 

Edit 7th July '16 12:11 GMT:
And if the booting is failing ... but you can read from the USB stick - boot it up from ROMMON.
Cisco router 2811 can work with 16GBs USB 3.0 stick.

In privileged enable mode issue commands:
sh file system
dir usbflash0:verify usbflash0:c2800nm-adventerprisek9_ivs-mz.151-4.M10.bin

if all is ok

conf t
config-reg 0x2100
do wr
^Z

reload

-- router is reloading (config-register is set!)

dev
dir usbflash0:
boot usbflash0:c2800nm-adventerprisek9_ivs-mz.151-4.M10.bin 


Booted up finally?? :s :) 

:: Note 1 ::
Having two identical 2811 - just one missing PVDM module -- one was working like a charm, second one i couldn't get to boot the right IOS from USB.

:: Note 2 ::

 Also tried few different USB sticks
-- Prolific 512MB -- doesn't work (USB Hub)

-- FlashTM 512 -- not working 
-- Samsung USB-DVD - not enough power



-- USB-SD-Reader - working! 

-- Kingston Datatraveler 3.0 16GB - working ok