Layer 2 Forwarding Protocol
Cisco VPN tunneling protocol
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]
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
- ^ RFC2341 on IETF.org
External links
- L2F on Cisco.com
- VPDN on Cisco.com
- L2TP on Cisco.com
- RFC2341 on IETF.org
- RFC2341 on RFC Archive
- v
- t
- e
Virtual private networking
- DTLS
- DirectAccess
- EVPN
- IPsec
- L2F
- L2TP
- L2TPv3
- PPTP
- SSTP
- Split tunneling
- SSL/TLS
- (Opportunistic: tcpcrypt)
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| Tesonet | |
| Ziff Davis |
