I believe that you require a PIX-535-UR-BUN and a PIX-535-FO-BUN to do the failover. One is in standby while the other carries data. They have to be connected by a special cable and a 10baseT connecion. You should verify this information with Cisco TAC before you order.
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...