L2F, or Layer 2 Forwarding, is a tunneling protocol developed by Cisco Systems, Inc. to establish virtual private network connections over the Internet. L2F does not provide encryption or confidentiality by itself; It relies on the protocol being tunneled to provide privacy. L2F was specifically designed to tunnel Point-to-Point Protocol (PPP) traffic.RFC2341 on IETF.org
Use Virtual dial-up allows many separate and autonomous protocol domains to share common access infrastructure including modems, Access Servers, and ISDN routers. RFCs prior to 2341 have specified protocols for supporting IP dial-up via SLIP and multiprotocol dial-up via PPP.
L2F packet structure Bits 0-12 13-15 16-23 24-31 F K P S 0 0 0 0 0 0 0 0 C Ver Protocol Sequence (opt) Multiplex ID Client ID Length Payload offset (opt) Packet key (optional) Payload L2F Checksum (opt)
Other VPN protocols IPsec L2TP Layer 2 Tunneling Protocol PPTP Point-to-Point Tunneling Protocol
References
External links L2F on Cisco.com VPDN on Cisco.com L2TP on Cisco.com RFC2341 on IETF.org RFC2341 on RFC Archive