to start with, you should identify firstly, the purpose of deploying the concentrator. is the objective to provide lan-lan vpn between branch office or remote vpn access for road warrior? you then need to decide whether authentication is against the local database or another authentication server, such as radius.
have a look at the url, you can find many many useful configuration examples.
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...