Layer 2 Forwarding Protocol

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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. [1]

Contents

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 0-1213-1516-2324-31
FKPS00000000CVerProtocolSequence (opt)
Multiplex IDClient ID
LengthPayload offset (opt)
Packet key (optional)

Payload
 L2F Checksum (opt)

Other VPN protocols

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