Layer 2 Forwarding Protocol
{{short description|Cisco VPN tunneling protocol}}
{{Refimprove|date=March 2020}}
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.[http://tools.ietf.org/html/rfc2341 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
| class="wikitable" style="text-align:center" |
| colspan="13" | Bits 0-12
! colspan="3" | 13-15 ! colspan="8" | 16-23 ! colspan="8" | 24-31 |
|---|
| colspan="1"| F
| colspan="1"| K | colspan="1"| P | colspan="1"| S | colspan="1"| 0 | colspan="1"| 0 | colspan="1"| 0 | colspan="1"| 0 | colspan="1"| 0 | colspan="1"| 0 | colspan="1"| 0 | colspan="1"| 0 | colspan="1"| C | colspan="3"| Ver | colspan="8"| Protocol | colspan="8"| Sequence (opt) |
| colspan="16" | Multiplex ID
| colspan="16" | Client ID |
| colspan="16" | Length
| colspan="16" | Payload offset (opt) |
| colspan="32" | Packet key (optional) |
| colspan="32" | Payload |
| colspan="16" style="border-top-style: hidden;" |
| colspan="16" | L2F Checksum (opt) |
Other VPN protocols
References
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External links
- [http://www.cisco.com/warp/public/732/L2F/ L2F on Cisco.com]
- [http://www.cisco.com/en/US/tech/tk801/tk703/tsd_technology_support_protocol_home.html VPDN on Cisco.com]
- [http://www.cisco.com/en/US/tech/tk827/tk369/tk388/tsd_technology_support_sub-protocol_home.html L2TP on Cisco.com]
- [http://tools.ietf.org/html/rfc2341 RFC2341 on IETF.org]
- [http://www.rfc-archive.org/getrfc.php?rfc=2341 RFC2341 on RFC Archive]
{{VPN}}