本文转自:https://www.cisco.com/c/en/us/td/docs/security/asa/asa98/configuration/vpn/asa-98-vpn-config/vpn-ike.html Chapter: IPsec and ISAKMP Chapter Contents About Tunneling, IPsec, and ISAKMPLicensing for IPsec VPNsGuidelines for IPsec VPNsConfigure IPsec About Tunneling, IPsec, and ISAKMP This topic describes the Internet Protocol Security (IPsec) and the Internet Security Association and Key Management Protocol (ISAKMP) standards used to build Virtual Private Networks (VPNs). Tunneling makes it possible to use a public TCP/IP network, such as the Internet, to create secure connections between remote users and a private corporate network. Each secure connection is called a tunnel. The ASA uses the ISAKMP and IPsec tunneling standards to build and manage tunnels. ISAKMP and IPsec accomplish the following: Negotiate tunnel parametersEstablish tunnelsAuthenticate users and dataManage security keysEncrypt and decrypt dataManage data transfer across the tunnel......Read More>