I kind of have the same problem, we have some 515e already in place with version 7.0(5) and bough FO's to add HA. However i cannot get them flashed. I found this article and i think it hints at the fact that they need to be plugged into a UR in order for the flash to work.. is this correct?
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
Table of Contents Introduction:This document describes details on how
NAT-T works. Background: ESP encrypts all critical information,
encapsulating the entire inner TCP/UDP datagram within an ESP header.
ESP is an IP protocol in the same sense that TCP an...