Cisco Layer Two Forwarding (Protocol) "L2F"

Virtual dial-up allows many separate and autonomous protocol domains to share common access infrastructure including modems, Access Servers, and ISDN routers. Previous RFCs have specified protocols for supporting IP dial-up via SLIP [1] and multiprotocol dial-up via PPP [2]. This document describes the Layer Two Forwarding protocol (L2F) which permits the tunneling of the link layer (i.e., HDLC, async HDLC, or SLIP frames) of higher level protocols. Using such tunnels, it is possible to divorce the location of the initial dial- up server from the location at which the dial-up protocol connection is terminated and access to the network provided.