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v6ops Working Group                                      G. Van de Velde
Internet-Draft                                          E. Levy-Abegnoli
Expires: July 31, 2008                                      C. Popoviciu
                                                           Cisco Systems
                                                              J. Mohacsi
                                                          NIIF/Hungarnet
                                                        January 28, 2008


                             IPv6 RA-Guard
                <draft-vandevelde-v6ops-ra-guard-01.txt>

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Copyright Notice

   Copyright (C) The IETF Trust (2008).

Abstract

   When using IPv6 within a single L2 network segment it is neccesary to
   ensure that all routers advertising their services within it are
   valid.  In cases where it is not convinient or possible to use SeND
   [1] a rogue Router Advertisement (RA) [2] could be sent by accident
   due to misconfiguraton or ill intended.  Simple solutions for



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   protecting against rogue RAs are beneficial in complementing SeND in
   securing the L2 domain for ceratin types of devices or in certain
   transitional situations.

   This document proposes a solution to reduce the threat of rogue RAs
   by enabling layer 2 devices to forward only RAs received over
   designated ports.


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  RA-guard as a deployment complement to SEND . . . . . . . . . . 3
   3.  RA-Guard state-machine  . . . . . . . . . . . . . . . . . . . . 3
     3.1.  RA-Guard state: OFF . . . . . . . . . . . . . . . . . . . . 4
     3.2.  RA-Guard state: LEARNING  . . . . . . . . . . . . . . . . . 4
     3.3.  RA-Guard state: ACTIVE  . . . . . . . . . . . . . . . . . . 4
   4.  RA-Guard interface states . . . . . . . . . . . . . . . . . . . 4
     4.1.  RA-Blocking interface . . . . . . . . . . . . . . . . . . . 4
     4.2.  RA-Forwarding interface . . . . . . . . . . . . . . . . . . 5
     4.3.  RA-Learning interface . . . . . . . . . . . . . . . . . . . 5
     4.4.  RA-Guard interface state transition . . . . . . . . . . . . 5
   5.  RA-Guard Use Considerations . . . . . . . . . . . . . . . . . . 5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
   7.  Security Considerations . . . . . . . . . . . . . . . . . . . . 6
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 6
   9.  Normative References  . . . . . . . . . . . . . . . . . . . . . 6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 6
   Intellectual Property and Copyright Statements  . . . . . . . . . . 8






















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1.  Introduction

   When operating IPv6 in a shared L2 network segment without complete
   SeND support by all devices connected or without the availability of
   the infrastructure neccesary to support SeND, there is always the
   risk of facing operational problems due to rogue Router
   Advertisements generated malliciously or unintentionaly by
   unauthorized or improperly configured routers connecting to the
   segment.

   There are several examples of work done on this topic which resulted
   in several related studies [3] [4] [5].This document describes a
   solution framework to the rogue-RA problem where network segments are
   designed around a single or a set of L2-switching devices capable of
   identifying invalid RAs and blocking them.  The solutions developed
   within this framework can span the spectrum from basic (where the
   port of the L2 device is statically instructed to forward or not to
   forward RAs received from the connected device) to advanced (where a
   criteria is used by the L2 device to dynamically validate or
   invalidate a received RA, this criteria can even be based on SeND
   mechanisms).


2.  RA-guard as a deployment complement to SEND

   RA-guard does not intend to provide a substitute for SeND based
   solutions.  It actually intends to provide complementary solutions in
   those environments where SeND might not be suitable or fully
   supported by all devices involved.  It may take time untill SeND is
   ubiquitous in IPv6 networks and some of its large scale deployment
   aspects are sorted out such as provisioning hosts with trust anchors.
   It is also reasonable to expect that some devices might not consider
   implementing SeND at all such as IPv6 enabled sensors.  The RA-guard
   "SeND-validating" RA on behalf of hosts would potentially simplify
   some of these challenges.

   RA-guard intends to provide simple solutions to the rogue-RA problem
   in such contexts and while in some cases it will do that through a
   simple solution, in others it leverages SEND between capable devices
   (L2 and routers) to provide protection to devices that do not
   consistently use SEND.


3.  RA-Guard state-machine

   RA-Guard runs on devices that provide connectivity between hosts and
   other hosts or networking devices.  An example of such RA-Guard
   capable device would be an OSI Layer-2 switch.  The capability can be



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   enabled globally at device level or at interface level.

   Depending on the mode of operation, the state-machine of the RA-Guard
   capability consists of three different states:
      State 1: OFF
      State 2: LEARNING
      State 3: ACTIVE

   The transition between these states can be triggered by manual
   configuration or by meeting a pre-defined criteria.

3.1.  RA-Guard state: OFF

   A device or interface in RA-Guard "OFF" state, operates as if the RA-
   Guard capability is not available.

3.2.  RA-Guard state: LEARNING

   A device or interface in the RA-Guard "Learning" state is actively
   acquiring information about the devices connected to its interfaces.
   The learning process takes place over a pre-defined period of time by
   capturing router advertisments or it can be event triggered.  The
   information gathered is compared against pre-defined criteria which
   qualify the validity of the RAs.

   In this state, the RA-Guard enabled device or interface is either
   blocking all RAs until their validity is verified or, alternatively
   it can temporarily forward the RAs until the decision is being made.

3.3.  RA-Guard state: ACTIVE

   A device or interface running RA-Guard and in Active state will block
   ingress RA-messages deemed invalid and will forward those deemed
   valid based on a pre-defined criteria defined.


4.  RA-Guard interface states

   The interfaces of devices with the RA-guard capability enabled can be
   in three possible states related to RA handling: Learning, Blocking
   and Forwarding.

4.1.  RA-Blocking interface

   An interface in the RA Blocking state blocks all ingress RA messages
   when RA-Guard capability is activated on a device.





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4.2.  RA-Forwarding interface

   An interface in the RA Forwarding state forwards all ingress RA
   messages deemed valid when RA-Guard capability is activated on a
   device.

4.3.  RA-Learning interface

   An interface in a RA Learning state snoops all received RAs and
   compares them against the criteria identifying valid RAs.  While in
   this state, the RAs can be blocked or forwarded until a decission is
   taken regarding their validity.

4.4.  RA-Guard interface state transition

   In the simplest cases, an RA-Guard enabled interface can be manually
   set in an RA-Blocking or RA-Forwarding state.  By default, the
   interfaces of the L2 switch could be set in RA-Blocking mode and
   enabled for forwarding by the network administrator.  In the more
   general case, the interface acquires RA information during the RA
   Learning state and by using a pre-defined validity criteria decides
   whether the analyzed RAs should be forwarded or blocked.  Based on
   this decission, the interface transitions into the RA Blocking or the
   RA Forwarding state.

   Upon detecting new RAs, a port can transition back into an RA-Guard
   Learning state.


5.  RA-Guard Use Considerations

   The RA-Guard mechanism is effective only when all mesages between
   IPv6 devices in the target environment traverse the controlled L2
   networking devices.  When on a shared media such as an Ethernet hub,
   devices can communicate directly without going through an RA-Guard
   capable L2 networking device.  In this scenario, the RA- Guard
   feature cannot protect against rogue-RAs.

   RA-Guard mecahnism does not protect against tunneled IPv6 traffic.


6.  IANA Considerations

   There are no extra IANA consideration for this document.







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7.  Security Considerations

   There are no extra Security consideration for this document.


8.  Acknowledgements

   The authors dedicate this document to the memory of Jun-ichiro Hagino
   (itojun) for his contributions to the development and deployment of
   IPv6.


9.  Normative References

   [1]  Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure
        Neighbor Discovery (SEND)", RFC 3971, March 2005.

   [2]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman, "Neighbor
        Discovery for IP version 6 (IPv6)", RFC 4861, September 2007.

   [3]  LORIA/INRIA, "NDPMon - IPv6 Neighbor Discovery Protocol Monitor
        (http://ndpmon.sourceforge.net/)", November 2007.

   [4]  KAME Project, "rafixd - developed at KAME - An active rogue RA
        nullifier
        (http://www.kame.net/dev/cvsweb2.cgi/kame/kame/kame/rafixd/)",
        November 2007.

   [5]  Hagino (itojun), Jun-ichiro., "Discussion of the various
        solutions (http://ipv6samurais.com/ipv6samurais/demystified/
        rogue-RA.html)", 2007.


Authors' Addresses

   Gunter Van de Velde
   Cisco Systems
   De Kleetlaan 6a
   Diegem  1831
   Belgium

   Phone: +32 2704 5473
   Email: gunter@cisco.com








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   Eric Levy Abegnoli
   Cisco Systems
   Village d'Entreprises Green Side - 400, Avenue Roumanille
   Biot - Sophia Antipolis, PROVENCE-ALPES-COTE D'AZUR  06410
   France

   Phone: +33 49 723 2620
   Email: elevyabe@cisco.com


   Ciprian Popoviciu
   Cisco Systems
   7025-6 Kit Creek Road
   Research Triangle Park, North Carolina  NC 27709-4987
   USA

   Phone: +1 919 392-3723
   Email: cpopovic@cisco.com


   Janos Mohacsi
   NIIF/Hungarnet
   18-22 Victor Hugo
   Budapest  H-1132
   Hungary

   Phone: tbc
   Email: mohacsi@niif.hu























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Full Copyright Statement

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