A tunnel is a link between two point. It can be a GRE tunnel (unencrypted) or a VPN tunnel(encrypted) or ... anything that create Point-2-Point link over a public network.
A VPN a create private network over a public network usually with encryption. To use encryption, you need to create tunnels( encrypt in one point, decrypt at the other). You can also have un-encrypted VPN. With MPLS-VPN, you create private network using tagging over you enterprise or service provider network.
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...