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Use of VLANs for IPv4-IPv6 Coexistence in Enterprise Networks
RFC 4554

Document type: RFC - Informational (June 2006)
Document stream: IETF
Last updated: 2013-03-02
Other versions: plain text, pdf, html

IETF State: (None)
Consensus: Unknown
Document shepherd: No shepherd assigned

IESG State: RFC 4554 (Informational)
Responsible AD: David Kessens
Send notices to: fred.baker@cisco.com, kurtis@kurtis.pp.se

Network Working Group                                           T. Chown
Request for Comments: 4554                     University of Southampton
Category: Informational                                        June 2006

     Use of VLANs for IPv4-IPv6 Coexistence in Enterprise Networks

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   Ethernet VLANs are quite commonly used in enterprise networks for the
   purposes of traffic segregation.  This document describes how such
   VLANs can be readily used to deploy IPv6 networking in an enterprise,
   which focuses on the scenario of early deployment prior to
   availability of IPv6-capable switch-router equipment.  In this
   method, IPv6 may be routed in parallel with the existing IPv4 in the
   enterprise and delivered at Layer 2 via VLAN technology.  The IPv6
   connectivity to the enterprise may or may not enter the site via the
   same physical link.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 2
   2.  Enabling IPv6 per Link  . . . . . . . . . . . . . . . . . . . . 3
       2.1.  IPv6 Routing over VLANs . . . . . . . . . . . . . . . . . 3
       2.2.  One VLAN per Router Interface . . . . . . . . . . . . . . 4
       2.3.  Collapsed VLANs on a Single Interface . . . . . . . . . . 4
       2.4.  Congruent IPv4 and IPv6 Subnets . . . . . . . . . . . . . 5
       2.5.  IPv6 Addressing . . . . . . . . . . . . . . . . . . . . . 5
       2.6.  Final IPv6 Deployment . . . . . . . . . . . . . . . . . . 5
   3.  Example VLAN Topology . . . . . . . . . . . . . . . . . . . . . 6
   4.  Security Considerations . . . . . . . . . . . . . . . . . . . . 7
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 7
   6.  Informative References  . . . . . . . . . . . . . . . . . . . . 7
   Appendix A.  Configuration Example  . . . . . . . . . . . . . . . . 8

Chown                        Informational                      [Page 1]
RFC 4554            VLANs for IPv4-IPv6 Coexistence            June 2006

1.  Introduction

   Ethernet VLANs are quite commonly used in enterprise networks for the
   purposes of traffic segregation.  This document describes how such
   VLANs can be readily used to deploy IPv6 networking in an enterprise,
   including the scenario of early deployment prior to availability of
   IPv6-capable switch-router equipment, where IPv6 may be routed in
   parallel with the existing IPv4 in the enterprise and delivered to
   the desired LANs via VLAN technology.

   It is expected that in the long run, sites migrating to dual-stack
   networking will either upgrade existing switch-router equipment to
   support IPv6 or procure new equipment that supports IPv6.  If a site
   already has production routers deployed that support IPv6, the
   procedures described in this document are not required.  In the
   interim, however, a method is required for early IPv6 adopters that
   enables IPv6 to be deployed in a structured, managed way to some or
   all of an enterprise network that currently lacks IPv6 support in its
   core infrastructure.

   The IEEE 802.1Q VLAN standard allows separate LANs to be deployed
   over a single bridged LAN, by inserting "Virtual LAN" tagging or
   membership information into Ethernet frames.  Hosts and switches that
   support VLANs effectively allow software-based reconfiguration of
   LANs through configuration of the tagging parameters.  The software
   control means that VLANs can be used to alter the LAN infrastructure
   without having to physically alter the wiring between the LAN
   segments and Layer 3 routers.

   Many IPv4 enterprise networks are utilising VLAN technology.  Where a
   site does not have IPv6-capable Layer 2/3 switch-router equipment,
   but VLANs are supported, a simple yet effective method exists to
   gradually introduce IPv6 to some or all of that site's network, in
   advance of the site's core infrastructure having dual-stack
   capability.

   If such a site wishes to introduce IPv6, it may do so by deploying a
   parallel IPv6 routing infrastructure (which is likely to be a
   different platform to the site's main infrastructure equipment, i.e.,
   one that supports IPv6 where the existing equipment does not), and
   then using VLAN technology to "overlay" IPv6 links onto existing IPv4
   links.  This can be achieved without needing any changes to the IPv4
   configuration.  The VLANs don't need to differentiate between IPv4
   and IPv6; the deployment is just dual-stack, as Ethernet is without
   VLANs.

Chown                        Informational                      [Page 2]

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