You didn't mention whether you're cosnidering IPsec using the legacy (discontinued) IPSec client or AnyConnect (IPsec via IKEv2). If you go the Anyconnect route, you will need to have AnyConnect Essentials license at a minumum to go beyond the two included AnyConnect Premium llicenses for remote access VPN.
Site-site IPsec VPN (up to 250 peers) is fine with the base licensing.
Note if you're considering an HA pair, you will require the Security Plus license on the 5512-X plaftorm. In this scenario it is usually preferable to just go ahead and order the 5515-X model. It doesn't require the Security Plus license and gives you a bit more throughput.
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...