Tunneling is a technique that enables remote access users to connect to a variety of network resources (Corporate Home Gateways or an Internet Service Provider) through a public data network. In general, tunnels established through the public network are point-to-point (though a multipoint tunnel is possible) and link a remote user to some resource at the far end of the tunnel. Major tunneling protocols (ie: Layer 2 Tunneling Protocol (L2TP), Point to Point Tunneling Protocol (PPTP), and Layer 2 Forwarding (L2F)) encapsulate Layer 2 traffic from the remote user and send it across the public network to the far end of the tunnel where it is de-encapsulated and sent to its destination. The most significant benefit of Tunneling is that it allows for the creation of VPNs over public data networks to provide cost savings for both end users, who do not have to create dedicated networks, and for Service Providers, who can leverage their network investments across many VPN customers.
Review additional information about Tunneling in the Technical Support site area.