According to the website, all you need is the serial number of your 11 rack.. This is from their website:

Q. I have Pro Tools LE. Can I move up to Pro Tools?
A. Yes. For a limited time, you can crossgrade to Pro Tools 11 for only $199 through 2014—that’s over 50% off the previous crossgrade pricing, and includes an upgrade/support plan for one year. To take advantage of this limited time offer, simply provide a hardware serial number (not your Pro Tools LE authorization code) for one of the following Avid audio interfaces at the time of purchase and activate your Pro Tools 11 software by December 31, 2014:

Mbox family (3rd generation)—Mbox Pro, Mbox, Mbox Mini
Eleven Rack
003 family—003 Rack, 003 Rack+, 003 (control surface)
Mbox 2 family (2nd generation)—Mbox 2 Pro, Mbox 2, Mbox 2 Mini, Mbox 2 Micro
Digi 002 family—Digi 002 Rack, Digi 002 (control surface)
VENUE family—VENUE | SC48, VENUE FWx Option Card