first configure your local computer to 192.168.1.23 then, install a ftp server (not tftp) place firmware.img into the root folder of this ftp server now go to 192.168.1.250 using your webbrowser and login with empty username and password admin use the firmware upgrade tab and use preflash.img as firmware upgrade file after the unit rebooted. go again to 192.168.1.250 with your webbrowser and visit http://192.168.1.250/upldadv.htm type in the following data in the provided fields hostname : 192.168.1.23 username: anonymous password: Image Path: / Image Name: 2nd.img then press update firmware consider that now just a "go back" button will be display. press it, then you will be redirected to the same page again now press "update firmware" again after the firmware has been flashed, press the "reboot ap" button which will be displayed