Module Summary IPsec is designed to provide interoperable, high-quality, cryptographically based security. An IPsec VPN is a VPN deployed on a shared infrastructure using IPsec encryption technology. There are several configuration items that must be enabled to implement IPsec using pre-shared keys. Cisco IOS PKI provides certificate management. GRE was developed to encapsulate a wide variety of protocol packet types inside IP tunnels. The DMVPN feature combines GRE tunnels, IPsec encryption, and NHRP routing. The Cisco IOS SSL VPN (WebVPN) feature provides support for remote- user access to enterprise networks from anywhere on the Internet. Cisco Easy VPN Remote access provides simple configuration of VPN access for remote users.