The client software has no cost. However the download page requires a service contract on an eligible ASA to download the current version. Otherwise you are limited to the version included on your ASA.
On the ASA itself the default license is 2 AnyConnect Premium client licenses. From there you can change to AnyConnect Essentials (which allows basic VPN for as many clients as the hardware supports) or additional AnyConnect Premium licenses (Premium is licensed in tiers - 10 user, 25, 50 etc.). Both of those "server-side" options have a cost.
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...