# References

For more information about the protocols for securing L2TP and IP tunnels with IPSec, consult the following resources:

- RFC 2401—Security Architecture for the Internet Protocol (November 1998)
- RFC 2661—Layer Two Tunneling Protocol “ L2TP” (August 1999)
- RFC 3193—Securing L2TP using IPSec (November 2001)
- RFC 3715—IPsec-Network Address Transation (NAT) Compatibility Requirements (March 2004)
- Negotiation of NAT-Traversal in the IKE—draft-ietf-ipsec-nat-t-ike-08.txt (July 2004 expiration)
- UDP Encapsulation of IPsec ESP Packets—draft-ietf-ipsec-udp-encaps-09.txt (November 2004 expiration)

  | Note: IETF drafts are valid for only 6 months from the date of issuance. They must be considered as works in progress. Please refer to the IETF Web site at http://www.ietf.org for the latest drafts.

For additional configuration information, see:

- Configuring IPSec
- Configuring Digital Certificates
- Configuring IP Tunnels
- L2TP Overview