Operations Area T. Chown Internet-Draft University of Southampton Expires: April 19, 2004 October 20, 2003 Use of VLANs for IPv4-IPv6 Coexistence in Enterprise Networks draft-chown-v6ops-vlan-usage-00 Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http:// www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on April 19, 2004. Copyright Notice Copyright (C) The Internet Society (2003). All Rights Reserved. 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, including the most likely scenario of subnets running IPv6 in parallel with the existing IPv4 subnets in the enterprise. The IPv6 connectivity to the enterprise may or may not enter the site via the same physical link. Chown Expires April 19, 2004 [Page 1] Internet-Draft Use of VLANs for IPv4-IPv6 Coexistence in Enterprise Networks October 2003 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Enabling IPv6 per subnet . . . . . . . . . . . . . . . . . . . 4 2.1 One VLAN per router interface . . . . . . . . . . . . . . . . 4 2.2 Collapsed VLANs on a single interface . . . . . . . . . . . . 4 2.3 Congruent IPv4 and IPv6 subnets . . . . . . . . . . . . . . . 4 3. Example VLAN topology . . . . . . . . . . . . . . . . . . . . 6 4. Security Considerations . . . . . . . . . . . . . . . . . . . 7 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 8 Normative References . . . . . . . . . . . . . . . . . . . . . 9 Author's Address . . . . . . . . . . . . . . . . . . . . . . . 9 Intellectual Property and Copyright Statements . . . . . . . . 10 Chown Expires April 19, 2004 [Page 2] Internet-Draft Use of VLANs for IPv4-IPv6 Coexistence in Enterprise Networks October 2003 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 subnets in an enterprise, including the most likely scenario of subnets running IPv6 in parallel with the existing IPv4 subnets in the enterprise. The IEEE 802.1Q VLAN standard allows separate LANs to be implemented 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 it is possible to bring in VLANs from separate places in the infrastructure without having to physically alter the wiring between the LAN segments and the IPv6 router. Many IPv4 enterprise networks will utilise VLAN technology. If such a site wishes to introduce IPv6, it may do so as described below, by "overlaying" IPv6 subnets onto existing IPv4 subnets, without needing any changes to the IPv4 configuration. The IPv6 connectivity to the enterprise may or may not enter the site via the same physical link. Chown Expires April 19, 2004 [Page 3] Internet-Draft Use of VLANs for IPv4-IPv6 Coexistence in Enterprise Networks October 2003 2. Enabling IPv6 per subnet The precise method by which IPv6 would be "injected" into the existing IPv4 network is implementation specific. The general principle is that the IPv6 router device (e.g. performing IPv6 Router Advertisements [1] in the case of stateless autoconfiguration) is connected to the target subnet through the use of VLAN capable Layer 2 equipment. 2.1 One VLAN per router interface In one case, an IPv6 router could be set up with an external interface connecting to the wider IPv6 internet, and any number of (IPv6-only) interfaces facing the internal network. The external interface may be dual-stack if some tunnel mechanism is used for external connectivity, or IPv6-only if a native connection is available. By connecting the internal interfaces directly to a VLAN-capable switch, VLAN tagging on each port of that switch can be used to create virtual LANs that will carry that traffic internally to IPv6 subnets that may be dispered widely across the internal network. The internal facing interfaces on the IPv6 edge router may feed other IPv6 routers over IPv6-only links which in turn inject the IPv6 connectivity (the /64 subnets and associated Router Advertisements) into the VLANs. It is not necessary to do VLAN tagging in all cases. On some Layer 3 switches, IPv6 traffic can directly be distributed to specific ports by adding them to the same protocol-based VLAN (in this case IPv6-based VLANs). 2.2 Collapsed VLANs on a single interface Many devices now support VLAN tagging based on virtual interfaces such that multiple IPv6 VLANs could be assigned from one physical router interface port. Thus it is possible to use just one router interface for "aggregated" VLAN trunking from a switch. 2.3 Congruent IPv4 and IPv6 subnets The VLAN technology can be used to deploy IPv6-only VLANs in an enterprise network. However most enterprises will be interested in dual-stack IPv4-IPv6 networking in the early stages of IPv6 deployment. In such a case the IPv6 connectivity may be injected into the Chown Expires April 19, 2004 [Page 4] Internet-Draft Use of VLANs for IPv4-IPv6 Coexistence in Enterprise Networks October 2003 existing IPv4 VLANs, such that the IPv4 and IPv6 subnets or links are congruent (i.e. they coincide exactly when superimposed). Such a method may have desirable administrative properties, e.g. the devices in each IPv4 subnet will be in the same IPv6 subnets also. Further, IPv6-only devices may be gradually added into the subnet without any need to resize the IPv6 subnet (which may hold in effect an infinite number of hosts in a /64 in contrast to IPv4 where the subnet size is often relatively limited). The lack of requirement to periodically resize an IPv6 subnet is a useful administrative advantage. Chown Expires April 19, 2004 [Page 5] Internet-Draft Use of VLANs for IPv4-IPv6 Coexistence in Enterprise Networks October 2003 3. Example VLAN topology The following figure shows how a VLAN topology may be used to introduce IPv6 in an enterprise network. (Subnet1) (Subnet2) (SubnetN) \ / | [Switch1] [SwitchN] \ / \ / ( VLAN infrastructure in the enterprise ) | [ Ethernet switch with VLAN support ] | FE/GE w/ VLAN tagging [ IPv6-router ] | ( connections to other IPv6 routers or the Internet ) ( also possibly the IPv4 connectivity ) Figure 1: IPv6 deployment using VLANs Chown Expires April 19, 2004 [Page 6] Internet-Draft Use of VLANs for IPv4-IPv6 Coexistence in Enterprise Networks October 2003 4. Security Considerations There are no additional security considerations particular to this method of enabling IPv6 on a subnet. Where the IPv6 connectivity is delivered into the enterprise network by a different path from the IPv4 connectivity, care should be given that equivalent application of security policy (e.g. firewalling) is made to the IPv6 path. Chown Expires April 19, 2004 [Page 7] Internet-Draft Use of VLANs for IPv4-IPv6 Coexistence in Enterprise Networks October 2003 5. Acknowledgements The author would like to thank colleagues on the 6NET project, where this technique for IPv4-IPv6 coexistence is widely deployed, including Janos Mohacsi (Hungarnet), Martin Dunmore and Chris Edwards (Lancaster University), Christian Strauf (JOIN Project, University of Muenster), Stig Venaas (UNINETT) and Pekka Savola (CSC/FUNET). Chown Expires April 19, 2004 [Page 8] Internet-Draft Use of VLANs for IPv4-IPv6 Coexistence in Enterprise Networks October 2003 Normative References [1] Narten, T., Nordmark, E. and W. Simpson, "Neighbor Discovery for IP Version 6 (IPv6)", RFC 2461, December 1998. Author's Address Tim Chown University of Southampton Southampton, Hampshire SO17 1BJ United Kingdom EMail: tjc@ecs.soton.ac.uk Chown Expires April 19, 2004 [Page 9] Internet-Draft Use of VLANs for IPv4-IPv6 Coexistence in Enterprise Networks October 2003 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11. 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This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION Chown Expires April 19, 2004 [Page 10] Internet-Draft Use of VLANs for IPv4-IPv6 Coexistence in Enterprise Networks October 2003 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Chown Expires April 19, 2004 [Page 11]