3 Dec 10 12:53
Thanks for your advice SYQUEST.
I finally got the answer for my question.
I will put it here just in case somebody experience the same problem:
First you have to know that, even if the IP option is available in bootstrap mode for the 1200s series, you cannot configure an IP address to any interface in bottstrap mode when connected on the console port.
The only way to be able to upload the firmware to the switch is to use the xmodem mode.
First change the speed of your console port by typing this:
bootstrap#console speed 115200 and hit enter.
Then close your terminal session (in my case, I used hyperterminal) and re-open a new one but this time change the speed of your connection from 9600 to 115200.
Once you are reconnected to the unit, type this:
copy xmodem flash and the name of the image of the firmware you want to copy on the unit. It should end by the extension .biz.
Then hit enter.
Now you will see some CCCCCC appears on the screen. Inside Hyperterminal, you have a choice of menus. Go into the Transfer menu.
In the menu, select send file.
A new window will appear. First browse for the firmware file that you have previously download from Adtran website.
In the second box, select xmodem for the protocole to use.
Finally, hit send.
Now, depending on the size of the file, it may take up to 20 minutes.
Once the transfer is done, type this:
bootstrap#boot system flash name_of_your_firmaware.biz and hit enter.
finally type bootstrap#reload and hit enter.
And that's it.
Your switch should boot normally from now on.