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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 (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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