Advisory Guidelines for 6to4 Deployment
RFC 6343

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Internet Engineering Task Force (IETF)                      B. Carpenter
Request for Comments: 6343                             Univ. of Auckland
Category: Informational                                      August 2011
ISSN: 2070-1721

                Advisory Guidelines for 6to4 Deployment

Abstract

   This document provides advice to network operators about deployment
   of the 6to4 technique for automatic tunneling of IPv6 over IPv4.  It
   is principally addressed to Internet Service Providers (ISPs),
   including those that do not yet support IPv6, and to Content
   Providers.  Some advice to implementers is also included.  The
   intention of the advice is to minimize both user dissatisfaction and
   help-desk calls.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6343.

Copyright Notice

   Copyright (c) 2011 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Carpenter                     Informational                     [Page 1]
RFC 6343                      6to4 Advisory                  August 2011

Table of Contents

   1. Introduction ....................................................2
   2. Principles of Operation .........................................3
      2.1. Router 6to4 ................................................3
      2.2. Anycast 6to4 ...............................................4
   3. Problems Observed ...............................................5
   4. Advisory Guidelines ............................................10
      4.1. Vendor Issues .............................................10
      4.2. Consumer ISPs, and Enterprise Networks, That Do
           Not Support IPv6 in Any Way ...............................11
           4.2.1. Anycast Address Availability .......................11
           4.2.2. Protocol 41 ........................................11
           4.2.3. IPv4 Prefix Issues .................................12
           4.2.4. DNS Issues .........................................12
           4.2.5. Rogue Router Advertisements ........................12
           4.2.6. Planning for IPv6 Deployment .......................13
      4.3. Consumer ISPs, and Enterprise Networks, That Do
           Support IPv6 ..............................................13
      4.4. Transit ISPs and Internet Exchange Points .................14
      4.5. Content Providers and Their ISPs ..........................15
   5. Tunnels Managed by ISPs ........................................17
   6. Security Considerations ........................................17
   7. Acknowledgements ...............................................18
   8. References .....................................................18
      8.1. Normative References ......................................18
      8.2. Informative References ....................................18

1.  Introduction

   A technique for automatic tunneling of IPv6 over IPv4, intended for
   situations where a user may wish to access IPv6-based services via a
   network that does not support IPv6, was defined a number of years
   ago.  It is known as 6to4 [RFC3056] [RFC3068] and is quite widely
   deployed in end systems, especially desktop and laptop computers.
   Also, 6to4 is supported in a number of popular models of CPE routers,
   some of which have it enabled by default, leading to quite widespread
   unintentional deployment by end users.

   Unfortunately, experience shows that the method has some problems in
   current deployments that can lead to connectivity failures.  These
   failures cause either long retry delays or complete failures for
   users trying to connect to services.  In many cases, the user may be
   quite unaware that 6to4 is in use; when the user contacts a help