I don't see why not. You can just connect the outside interface of the old PIX onto the inside segment of the failover pair, and put your DMZ servers behind the old PIX. You'll have to set up static's and ACL's on both the failover pair and the old PIX to allow the traffic through, plus make sure you add static routes so that each PIX knows how to get everywhere, and you should be good to go.
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...
[toc:faq]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 and UDP are I...