L2F

The L2F (Layer 2 Forwarding) protocol was created in the early stages of virtual private network development. Like PPTP, L2F was designed by Cisco to establish traffic tunnels from remote users to their corporate headquarters. The main difference between PPTP and L2F is that, since the establishment of L2F tunnels does not depend on the IP protocol (Internet Protocol), it is capable of working directly with other media, such as Frame Relay or ATM. Like PPTP, L2F uses the PPP protocol for remote user authentication, but also implements other authentication systems such as Terminal Access Controller Access Control System (TACACS+) and Remote Authentication Dial-In (RADIUS). User Service). L2F also differs from PPTP in that it allows tunnels to contain more than one connection.

There are two levels of user authentication, first by the ISP (network service provider), prior to the establishment of the tunnel, and later, when the connection with the corporate gateway has been established. Since L2F is a Data Link Layer protocol according to the OSI Reference Model, it offers users the same flexibility as PPTP to handle non-IP protocols, such as IPX or NetBEUI.

Structure of an L2F packet