Going from 8.2 to 8.3 was a BIG change. Going from 8.4 to 9.x is not so big a change. Certainly some things will change and some things will be added in the new version. So you need to check the documentation and especially the release notes. If you have opportunity to test the upgrade with a machine that is not in production that would be very good. But overall I do not remember any big changes that would impact your upgrade.
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...