An Anycast Prefix for 6to4 Relay Routers
RFC 3068

Document Type RFC - Historic (June 2001; No errata)
Obsoleted by RFC 7526
Author Christian Huitema 
Last updated 2015-10-14
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IESG IESG state RFC 3068 (Historic)
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Which proposes to obsolete:

RFC 3068


RFC 6732
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Network Working Group                                         C. Huitema
Request for Comments: 3068                                     Microsoft
Category: Standards Track                                      June 2001

                An Anycast Prefix for 6to4 Relay Routers

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2001).  All Rights Reserved.


   This memo introduces a "6to4 anycast address" in order to simplify
   the configuration of 6to4 routers.  It also defines how this address
   will be used by 6to4 relay routers, how the corresponding "6to4
   anycast prefix" will be advertised in the IGP and in the EGP.  The
   memo documents the reservation by IANA (Internet Assigned Numbers
   Authority) of the "6to4 relay anycast prefix."

1 Introduction

   According to [RFC3056], there are two deployment options for a 6to4
   routing domain, depending on whether or not the domain is using an
   IPv6 exterior routing protocol.  If a routing protocol is used, then
   the 6to4 routers acquire routes to all existing IPv6 networks through
   the combination of EGP and IGP.  If no IPv6 exterior routing protocol
   is used, the 6to4 routers using a given relay router each have a
   default IPv6 route pointing to the relay router.  This second case is
   typically used by small networks; for these networks, finding and
   configuring the default route is in practice a significant hurdle.
   In addition, even when the managers of these networks find an
   available route, this route often points to a router on the other
   side of the Internet, leading to very poor performance.

   The operation of 6to4 routers requires either that the routers
   participate in IPv6 inter-domain routing, or that the routers be
   provisioned with a default route.  This memo proposes a standard
   method to define the default route.  It introduces the IANA assigned
   "6to4 Relay anycast prefix" from which 6to4 packets will be

Huitema                     Standards Track                     [Page 1]
RFC 3068        An Anycast Prefix for 6to4 Relay Routers       June 2001

   automatically routed to the nearest available router.  It allows the
   managers of the 6to4 relay routers to control the sources authorized
   to use their resource.  It makes it easy to set up a large number of
   6to4 relay routers, thus enabling scalability.

2 Definitions

   This memo uses the definitions introduced in [RFC3056], in particular
   the definition of a 6to4 router and a 6to4 Relay Router. It adds the
   definition of the 6to4 Relay anycast prefix, 6to4 Relay anycast
   address, 6to4 IPv6 relay anycast address, and Equivalent IPv4 unicast

2.1 6to4 router (or 6to4 border router)

   An IPv6 router supporting a 6to4 pseudo-interface.  It is normally
   the border router between an IPv6 site and a wide-area IPv4 network.

2.2 6to4 Relay Router

   A 6to4 router configured to support transit routing between 6to4
   addresses and native IPv6 addresses.

2.3 6to4 Relay anycast prefix

   An IPv4 address prefix used to advertise an IPv4  route to an
   available 6to4 Relay Router, as defined in this memo.

   The value of this prefix is

2.4 6to4 Relay anycast address

   An IPv4 address used to reach the nearest 6to4 Relay Router, as
   defined in this memo.

   The address corresponds to host number 1 in the 6to4 Relay anycast

2.5 6to4 IPv6 relay anycast address

   The IPv6 address derived from the 6to4 Relay anycast address
   according to the rules defined in 6to4, using a null prefix and a
   null host identifier.

   The value of the address is "2002:c058:6301::".

Huitema                     Standards Track                     [Page 2]
RFC 3068        An Anycast Prefix for 6to4 Relay Routers       June 2001

2.6 Equivalent IPv4 unicast address

   A regular IPv4 address associated with a specific 6to4 Relay Router.
   Packets sent to that address are treated by the 6to4 Relay Router as
   if they had been sent to the 6to4 Relay anycast address.

3 Model, requirements

   Operation of 6to4 routers in domains that don't run an IPv6 EGP
   requires that these routers be configured with a default route to the
   IPv6 Internet.  This route will be expressed as a 6to4 address. The
   packets bound to this route will be encapsulated in IPv4 whose source
   will be an IPv4 address associated to the 6to4 router, and whose
   destination will be the IPv4 address that is extracted from the
   default route.  We want to arrive at a model of operation in which
   the configuration is automatic.
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