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INFORMATIONAL
Internet Engineering Task Force (IETF)                          T. ChownRequest for Comments: 6104                     University of SouthamptonCategory: Informational                                        S. VenaasISSN: 2070-1721                                            Cisco Systems                                                           February 2011Rogue IPv6 Router Advertisement Problem StatementAbstract   When deploying IPv6, whether IPv6-only or dual-stack, routers are   configured to send IPv6 Router Advertisements (RAs) to convey   information to nodes that enable them to autoconfigure on the   network.  This information includes the implied default router   address taken from the observed source address of the RA message, as   well as on-link prefix information.  However, unintended   misconfigurations by users or administrators, or possibly malicious   attacks on the network, may lead to bogus RAs being present, which in   turn can cause operational problems for hosts on the network.  In   this document, we summarise the scenarios in which rogue RAs may be   observed and present a list of possible solutions to the problem.  We   focus on the unintended causes of rogue RAs in the text.  The goal of   this text is to be Informational, and as such to present a framework   around which solutions can be proposed and discussed.Status of This Memo   This document is not an Internet Standards Track specification; it is   published for informational purposes.   This document is a product of the Internet Engineering Task Force   (IETF).  It represents the consensus of the IETF community.  It has   received public review and has been approved for publication by the   Internet Engineering Steering Group (IESG).  Not all documents   approved by the IESG are a candidate for any level of Internet   Standard; seeSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc6104.Chown & Venaas                Informational                     [Page 1]

RFC 6104            Rogue IPv6 Router Advertisements       February 2011Copyright Notice   Copyright (c) 2011 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents   (http://trustee.ietf.org/license-info) in effect on the date of   publication of this document.  Please review these documents   carefully, as they describe your rights and restrictions with respect   to this document.  Code Components extracted from this document must   include Simplified BSD License text as described in Section 4.e of   the Trust Legal Provisions and are provided without warranty as   described in the Simplified BSD License.   This document may contain material from IETF Documents or IETF   Contributions published or made publicly available before November   10, 2008.  The person(s) controlling the copyright in some of this   material may not have granted the IETF Trust the right to allow   modifications of such material outside the IETF Standards Process.   Without obtaining an adequate license from the person(s) controlling   the copyright in such materials, this document may not be modified   outside the IETF Standards Process, and derivative works of it may   not be created outside the IETF Standards Process, except to format   it for publication as an RFC or to translate it into languages other   than English.Chown & Venaas                Informational                     [Page 2]

RFC 6104            Rogue IPv6 Router Advertisements       February 2011Table of Contents1. Introduction ....................................................42. Bogus RA Scenarios ..............................................42.1. Administrator Misconfiguration .............................52.2. User Misconfiguration ......................................52.3. Malicious Misconfiguration .................................53. Methods to Mitigate against Rogue RAs ...........................63.1. Manual Configuration .......................................63.2. Introducing RA Snooping ....................................63.3. Using ACLs on Managed Switches .............................73.4. SEcure Neighbor Discovery (SEND) ...........................73.5. Router Preference Option ...................................83.6. Relying on Layer 2 Admission Control .......................83.7. Using Host-Based Packet Filters ............................83.8. Using an "Intelligent" Deprecation Tool ....................83.9. Using Layer 2 Partitioning .................................93.10. Adding Default Gateway/Prefix Options to DHCPv6 ...........94. Scenarios and Mitigations ......................................105. Other Related Considerations ...................................115.1. Unicast RAs ...............................................115.2. The DHCP versus RA Threat Model ...........................115.3. IPv4-Only Networks ........................................125.4. Network Monitoring Tools ..................................125.5. Recovering from Bad Configuration State ...................125.6. Isolating the Offending Rogue RA Source ...................136. Conclusions ....................................................137. Security Considerations ........................................148. Acknowledgments ................................................149. Informative References .........................................15Chown & Venaas                Informational                     [Page 3]

RFC 6104            Rogue IPv6 Router Advertisements       February 20111.  Introduction   The Neighbor Discovery protocol [RFC4861] describes the operation of   IPv6 Router Advertisements (RAs) that are used to determine node   configuration information during the IPv6 autoconfiguration process,   whether that node's configuration is stateful, via the Dynamic Host   Configuration Protocol for IPv6 (DHCPv6) [RFC3315] or stateless, as   per [RFC4862], possibly in combination with DHCPv6 Light [RFC3736].   In observing the operation of deployed IPv6 networks, it is apparent   that there is a problem with undesired or "bogus" IPv6 RAs appearing   on network links or subnets.  By "bogus" we mean RAs that were not   the intended configured RAs, but rather RAs that have appeared for   some other reason.  While the problem appears more common in shared   wireless environments, it is also seen on wired enterprise networks.   The problem with rogue RAs is that they can cause partial or complete   failure of operation of hosts on an IPv6 link.  For example, the   default router address is drawn directly from the source address of   the RA message.  In addition, rogue RAs can cause hosts to assume   wrong prefixes to be used for stateless address autoconfiguration.   In a case where there may be mixing of "good" and "bad" RAs, a host   might keep on using the "good" default gateway, but pick a wrong   source address, leading to egress filtering problems.  As such, rogue   RAs are an operational issue for which solution(s) are required, and   for which best practice needs to be conveyed.  This not only includes   preventing or detecting rogue RAs, but also where necessary ensuring   the network (and hosts on the network) have the ability to quickly   recover from a state where host configuration is incorrect as a   result of processing such an RA.   In the next section, we discuss the scenarios that may give rise to   rogue RAs being present.  In the following section, we present some   candidate solutions for the problem, some of which may be more   practical to deploy than others.  This document focuses on   "accidental" rogue RAs; while malicious RAs are of course also   possible, the common problem today lies with unintended RAs.  In   addition, a network experiencing malicious attack of this kind is   likely to also experience malicious Neighbor Advertisement (NA) and   related messages.2.  Bogus RA Scenarios   There are three broad classes of scenario in which bogus RAs may be   introduced to an IPv6 network.Chown & Venaas                Informational                     [Page 4]

RFC 6104            Rogue IPv6 Router Advertisements       February 20112.1.  Administrator Misconfiguration   Here an administrator incorrectly configures RAs on a router   interface, causing incorrect RAs to appear on links and causing hosts   to generate incorrect or unintended IPv6 address, gateway, or other   information.  In such a case, the default gateway may be correct, but   a host might for example become multiaddressed, possibly with a   correct and incorrect address based on a correct and incorrect   prefix.  There is also the possibility of other configuration   information being misconfigured, such as the lifetime option.   In the case of a Layer 2 IEEE 802.1Q Virtual LAN (VLAN)   misconfiguration, RAs may "flood" to unintended links, causing hosts   or more than one link to potentially become incorrectly   multiaddressed, with possibly two different default routers   available.2.2.  User Misconfiguration   In this case, a user's device "accidentally" transmits RAs onto the   local link, potentially adding an additional default gateway and   associated prefix information.   This seems to typically be seen on wireless (though sometimes wired)   networks where a laptop has enabled the Windows Internet Connection   Sharing (ICS) service, which can turn a host into a 6to4 [RFC3056]   gateway; this can be a useful feature, unless of course it is run   when not intended.  This service can also cause IPv4 problems, as it   will typically start a "rogue" DHCPv4 server on the host.   We have also had reports that hosts may not see genuine IPv6 RAs on a   link due to host firewalls, causing them to turn on a connection-   sharing service and 6to4 as a result.  In some cases, more technical   users may also use a laptop as a home gateway (e.g., again a 6to4   gateway) and then connect to another network, forgetting their   previous gateway configuration is still active.   There are also reported incidents in enterprise networks of users   physically plugging Ethernet cables into the wrong sockets and   bridging two subnets together, causing a problem similar to VLAN   flooding.2.3.  Malicious Misconfiguration   Here an attacker is deliberately generating RAs on the local network   in an attempt to perform some form of denial-of-service or man-in-   the-middle attack.Chown & Venaas                Informational                     [Page 5]

RFC 6104            Rogue IPv6 Router Advertisements       February 2011   As stated above, while this is a genuine concern for network   administrators, there have been few if any reports of such activity,   while in contrast reports of accidental rogue RAs are very   commonplace.  In writing this text, and with the feedback of the   v6ops working group, we came to the conclusion that the issue of   malicious attack, due to the other complementary attacks that are   likely to be launched using rogue NA and similar messages, are best   considered by further work and document(s).  As a result, this text   intends to provide informational guidance for operators looking for   practical measures to take to avoid "accidental" rogue RAs on their   own networks.3.  Methods to Mitigate against Rogue RAs   In this section, we present a summary of methods suggested to date   for reducing or removing the possibility of rogue RAs being seen on a   network.3.1.  Manual Configuration   The default gateway and host address can usually be manually   configured on a node.  This of course can be a resource intensive   solution, and also prone to administrative mistakes in itself.   Manual configuration implies that RA processing is disabled.  Most   operating systems allow RA messages to be ignored, such that if an   IPv6 address is manually configured on a system, an additional global   autoconfigured address will not be added should an unexpected RA   appear on the link.3.2.  Introducing RA Snooping   It should be possible to implement "RA snooping" in Layer 2 switches   in a similar way to DHCP snooping, such that RAs observed from   incorrect sources are blocked or dropped, and not propagated through   a subnet.  One candidate solution in this space, called "RA-Guard"   [RFC6105], has been proposed.  This type of solution has appeal   because it is a familiar model for enterprise network managers, but   it can also be used to complement SEcure Neighbor Discovery (SEND)   [RFC3971], by a switch acting as a SEND proxy for hosts.   This type of solution may not be applicable everywhere, e.g., in   environments where there are not centrally controlled or manageable   switches.Chown & Venaas                Informational                     [Page 6]

RFC 6104            Rogue IPv6 Router Advertisements       February 20113.3.  Using ACLs on Managed Switches   Certain switch platforms can already implement some level of rogue RA   filtering by the administrator configuring Access Control Lists   (ACLs) that block RA ICMP messages that might be inbound on "user"   ports.  Again this type of "solution" depends on the presence of such   configurable switches.   A recent document describes the RA message format(s) for filtering   [IPv6-AUTOCFG-FILTER].  The document also notes requirements for   DHCPv6 snooping, which can then be implemented similarly to DHCPv4   snooping.3.4.  SEcure Neighbor Discovery (SEND)   The SEcure Neighbor Discovery (SEND) [RFC3971] protocol provides a   method for hosts and routers to perform secure Neighbor Discovery.   Thus, it can in principle protect a network against rogue RAs.   SEND is not yet widely used at the time of writing, in part because   there are very few implementations of the protocol.  Some other   deployment issues have been raised, though these are likely to be   resolved in due course.  For example, routers probably don't want to   use autogenerated addresses (which might need to be protected by   ACLs), so SEND needs to be shown to work with non-autogenerated   addresses.  Also, it has been argued that there are "bootstrapping"   issues, in that hosts wanting to validate router credentials (e.g.,   to a certificate server or Network Time Protocol (NTP) server) are   likely to need to communicate via the router for that information.   Further, it's not wholly clear how widely adopted SEND could or would   be in site networks with "lightweight" security (e.g., many campus   networks), especially where hosts are managed by users and not   administratively.  Public or conference wireless networks may face   similar challenges.  There may also be networks, like perhaps sensor   networks, where use of SEND is less practical.  These networks still   require rogue RA protection.   While SEND clearly can provide a good, longer-term solution,   especially in networks where malicious activity is a significant   concern, there is a requirement today for practical solutions, and/or   solutions more readily applicable in more "relaxed" environments.  In   the latter case, solutions like "RA snooping" or applied ACLs are   more attractive now.Chown & Venaas                Informational                     [Page 7]

RFC 6104            Rogue IPv6 Router Advertisements       February 20113.5.  Router Preference Option   [RFC4191] introduced a Router Preference option, such that an RA   could carry one of three Router Preference values: High, Medium   (default), or Low.  Thus, an administrator could use "High" settings   for managed RAs, and hope that "accidental" RAs would be medium   priority.  This of course would only work in some scenarios -- if the   user who accidentally sends out a rogue RA on the network has   configured their device with "High" precedence for their own intended   usage, the priorities would clash.  But for accidental rogue RAs   caused by software like Windows ICS and 6to4, which would use the   default precedence, it could be useful.  Obviously this solution   would also rely on clients (and routers) having implementations of   the Router Preference option.3.6.  Relying on Layer 2 Admission Control   In principle, if a technology such as IEEE 802.1x is used, devices   would first need to authenticate to the network before being able to   send or receive IPv6 traffic.  Ideally, authentication would be   mutual.  Deployment of 802.1x, with mutual authentication, may   however be seen as somewhat "heavyweight", akin to SEND, for some   deployments.   Improving Layer 2 security may help to mitigate against an attacker's   capability to join the network to send RAs, but it doesn't prevent   misconfiguration issues.  A user can happily authenticate and still   launch a Windows ICS service, for example.3.7.  Using Host-Based Packet Filters   In a managed environment, hosts could be configured via their   "personal firewall" to only accept RAs from trusted sources.  Hosts   could also potentially be configured to discard 6to4-based RAs in a   managed enterprise environment.   However, the problem is then pushed to keeping this configuration   maintained and correct.  If a router fails and is replaced, possibly   with a new Layer 2 interface address, the link local source address   in the filter may become incorrect, and thus no method would be   available to push the new information to the host over the network.3.8.  Using an "Intelligent" Deprecation Tool   It is possible to run a daemon on a link (perhaps on the router on   the link) to watch for incorrect RAs and to send a deprecating RA   with a router lifetime of zero when such an RA is observed.  The KAME   rafixd is an example of such a tool, which has been used at IETFChown & Venaas                Informational                     [Page 8]

RFC 6104            Rogue IPv6 Router Advertisements       February 2011   meetings with some success.  A slightly enhanced tool called RAMOND   has since been developed from this code, and is now available as a   Sourceforge project.  As with host-based firewalling, the daemon   would need to somehow know what "good" and "bad" RAs are, from some   combination of known good sources and/or link prefixes.  In an   environment with native IPv6, though, 6to4-based RAs would certainly   be known to be rogue.   Whether or not use of such a tool is the preferred method, monitoring   a link for observed RAs seems prudent from a network management   perspective.  Some such tools exist already, e.g., NDPMon, which can   also detect other undesirable behaviour.3.9.  Using Layer 2 Partitioning   If each system or user on a network is partitioned into a different   Layer 2 medium, then the impact of rogue RAs can be limited.  In   broadband networks, bridging [RFC2684] may be available, for example.   The benefit may be scenario-specific, e.g., whether a given user or   customer has their own network prefix or whether the provisioning is   in a shared subnet or link.  It is certainly desirable that any given   user or customer's system(s) are unable to see RAs that may be   generated by other users or customers.   However, such partitioning would probably increase address space   consumption significantly if applied in enterprise networks, and in   many cases, hardware costs and software licensing costs to enable   routing to the edge can be quite significant.3.10.  Adding Default Gateway/Prefix Options to DHCPv6   Adding Default Gateway and Prefix options for DHCPv6 would allow   network administrators to configure hosts to only use DHCPv6 for   default gateway and prefix configuration in managed networks, where   RAs would be required today.  A new document has proposed such a   default router option, along with prefix advertisement options for   DHCPv6 [DHCPv6-DEFAULT-RTR].  Even with such options added to DHCPv6,   an RA is in principle still required to inform hosts to use DHCPv6.   An advantage of DHCPv6 is that should an error be introduced, only   hosts that have refreshed their DHCP information since that time are   affected, while a multicast rogue RA will most likely affect all   hosts immediately.  DHCPv6 also allows different answers to be given   to different hosts.   While making host configuration possible via DHCPv6 alone is a viable   option that would allow IPv6 configuration to be done in a way   similar to IPv4 today, the problem has only been shifted: rather thanChown & Venaas                Informational                     [Page 9]

RFC 6104            Rogue IPv6 Router Advertisements       February 2011   rogue RAs being the problem, rogue DHCPv6 servers would be an   equivalent issue.  As with IPv4, a network would then still require   use of Authenticated DHCP, or DHCP(v6) snooping, as suggested in   [IPv6-AUTOCFG-FILTER].   There is certainly some demand in the community for DHCPv6-only host   configuration.  While this may mitigate the rogue RA issue, it simply   moves the trust problem elsewhere, albeit to a place administrators   are familiar with today.4.  Scenarios and Mitigations   In this section, we summarise the error/misconfiguration scenarios   and practical mitigation methods described above in a matrix format.   We consider, for the case of a rogue multicast RA, which of the   mitigation methods helps protect against administrator and user   errors.  For the administrator error, we discount an error in   configuring the countermeasure itself; rather, we consider an   administrator error to be an error in configuration elsewhere in the   network.        +------------------------+---------------------------+        |                        |         Scenario          |        |       Mitigation       |---------------------------|        |         Method         | Admin Error | User Error  |        +------------------------+-------------+-------------+        | Manual configuration   |     Y       |      Y      |        +------------------------+-------------+-------------+        | SEND                   |     Y       |      Y      |        +------------------------+-------------+-------------+        | RA snooping            |     Y       |      Y      |        +------------------------+-------------+-------------+        | Use switch ACLs        |     Y       |      Y      |        +------------------------+-------------+-------------+        | Router preference      |     N       |      Y      |        +------------------------+-------------+-------------+        | Layer 2 admission      |     N       |      N      |        +------------------------+-------------+-------------+        | Host firewall          |     Y       |      Y      |        +------------------------+-------------+-------------+        | Deprecation daemon     |     Y       |      Y      |        +------------------------+-------------+-------------+        | Layer 2 partition      |     N       |      Y      |        +------------------------+-------------+-------------+        | DHCPv6 gateway option  |   Partly    |  If Auth    |        +------------------------+-------------+-------------+Chown & Venaas                Informational                    [Page 10]

RFC 6104            Rogue IPv6 Router Advertisements       February 2011   What the above summary does not consider is the practicality of   deploying the measure.  An easy-to-deploy method that buys improved   resilience to rogue RAs without significant administrative overhead   is attractive.  On that basis, the RA snooping proposal, e.g.,   RA-Guard, has merit, while approaches like manual configuration are   less appealing.  However, RA-Guard is not yet fully defined or   available, while only certain managed switch equipment may support   the required ACLs.5.  Other Related Considerations   There are a number of related issues that have come out of   discussions on the rogue RA topic, which the authors believe are   worth capturing in this document.5.1.  Unicast RAs   The above discussion was initially held on the assumption that rogue   multicast RAs were the cause of problems on a shared network subnet.   However, the specifications for Router Advertisements allow them to   be sent unicast to a host, as perSection 6.2.6 of RFC 4861.  If a   host sending rogue RAs sends them unicast to the soliciting host,   that RA may not be seen by other hosts on the shared medium, e.g., by   a monitoring daemon.  In most cases, though, an accidental rogue RA   is likely to be multicast.5.2.  The DHCP versus RA Threat Model   Comparing the threat model for rogue RAs and rogue DHCPv6 servers is   an interesting exercise.  In the case of Windows ICS causing rogue   6to4-based RAs to appear on a network, it is very likely that the   same host is also acting as a rogue IPv4 DHCP server.  The rogue   DHCPv4 server can allocate a default gateway and an address to hosts,   just as a rogue RA can lead hosts to learning of a new (additional)   default gateway, prefix(es), and address.  In the case of multicast   rogue RAs, however, the impact is potentially immediate to all hosts,   while the rogue DHCP server's impact will depend on lease timers for   hosts.   In principle, Authenticated DHCP can be used to protect against rogue   DHCPv4 (and DHCPv6) servers, just as SEND could be used to protect   against rogue IPv6 RAs.  However, actual use of Authenticated DHCP in   typical networks is currently minimal.  Were new DHCPv6 default   gateway and prefix options to be standardised as described above,   then without Authenticated DHCP the (lack of) security is just pushed   to another place.Chown & Venaas                Informational                    [Page 11]

RFC 6104            Rogue IPv6 Router Advertisements       February 2011   The RA-Guard approach is essentially using a similar model to DHCP   message snooping to protect against rogue RAs in network (switch)   equipment.  As noted above, DHCPv6 message snooping would also be   very desirable in IPv6 networks.5.3.  IPv4-Only Networks   The rogue RA problem should also be considered by administrators and   operators of IPv4-only networks, where IPv6 monitoring, firewalling,   and other related mechanisms may not be in place.   For example, a comment has been made that in the case of 6to4 being   run by a host on a subnet that is not administratively configured   with IPv6, some OSes or applications may begin using IPv6 to the 6to4   host (router) rather than IPv4 to the intended default IPv4 router,   because they have IPv6 enabled by default and some applications   prefer IPv6 by default.  Technically aware users may also   deliberately choose to use IPv6, possibly for subversive reasons.   Mitigating against this condition can also be seen to be important.5.4.  Network Monitoring Tools   It would generally be prudent for network monitoring or management   platforms to be able to observe and report on observed RAs, and   whether unintended RAs (possibly from unintended sources) are present   on a network.  Further, it may be useful for individual hosts to be   able to report their address status (assuming their configuration   status allowed it, of course), e.g., this could be useful during an   IPv6 renumbering phased process as described inRFC 4192 [RFC4192].   The above assumes, of course, that what defines a "good" (or "bad")   RA can be configured in a trustworthy manner within the network's   management framework.5.5.  Recovering from Bad Configuration State   After a host receives and processes a rogue RA, it may have multiple   default gateways, global addresses, and potentially clashing RA   options (e.g., M/O bits [RFC4861]).  The host's behaviour may then be   unpredictable, in terms of the default router that is used, and the   (source) address(es) used in communications.  A host that is aware of   protocols such as Shim6 [RFC5533] may believe it is genuinely   multihomed.Chown & Venaas                Informational                    [Page 12]

RFC 6104            Rogue IPv6 Router Advertisements       February 2011   An important issue is how readily a host can recover from receiving   and processing bad configuration information, e.g., considering the   "2 hour rule" mentioned inSection 5.5.3 of RFC 4862 (though this   applies to the valid address lifetime and not the router lifetime).   We should ensure that methods exist for a network administrator to   correct bad configuration information on a link or subnet, and that   OS platforms support these methods.  At least if the problem can be   detected, and corrected promptly, the impact is minimised.5.6.  Isolating the Offending Rogue RA Source   In addition to issuing a deprecating RA, it would be desirable to   isolate the offending source of the rogue RA from the network.  It   may be possible to use Network Access Control methods to quarantine   the offending host, or rather the network point of attachment or port   that it is using.6.  Conclusions   In this text we have described scenarios via which rogue Router   Advertisements (RAs) may appear on a network, and some measures that   could be used to mitigate against these.  We have also noted some   related issues that have arisen in the rogue RA discussions.  Our   discussion is generally focused on the assumption that rogue RAs are   appearing as a result of accidental misconfiguration on the network,   by a user or administrator.   While SEND perhaps offers the most robust solution, implementations   and deployment guidelines are not yet widely available.  SEND is very   likely to be a good, longer-term solution, but many administrators   are seeking solutions today.  Such administrators are also often in   networks with security models for which SEND is a "heavyweight"   solution, e.g., campus networks, or wireless conference or public   networks.  For such scenarios, simpler measures are desirable.   Adding new DHCPv6 Default Gateway and Prefix options would allow IPv6   host configuration by DHCP only and would be a method that IPv4   administrators are comfortable with (for better or worse), but this   simply shifts the robustness issue elsewhere.   While a number of the mitigations described above have their appeal,   the simplest solutions probably lie in switch-based ACLs and   RA-Guard-style approaches.  Where managed switches are not available,   use of the Router Preference option and (more so in managed desktop   environments) host firewalls may be appropriate.Chown & Venaas                Informational                    [Page 13]

RFC 6104            Rogue IPv6 Router Advertisements       February 2011   In the longer term, wider experience of SEND will be beneficial,   while the use of RA snooping will remain useful either to complement   SEND (where a switch running RA-Guard can potentially be a SEND   proxy) or to assist in scenarios for which SEND is not deployed.7.  Security Considerations   This Informational document is focused on discussing solutions to   operational problems caused by rogue RAs resulting from unintended   misconfiguration by users or administrators.  Earlier versions of   this text included some analysis of rogue RAs introduced maliciously;   e.g., the text included an extra column in the matrix inSection 4.   However, the consensus of the v6ops working group feedback was to   instead focus on the common operational problem of "accidental" rogue   RAs seen today.   Thus, the final version of this text does not address attacks on a   network where rogue RAs are intentionally introduced as part of a   broader attack, e.g., including malicious NA messages.  On the wire,   malicious rogue RAs will generally look the same as "accidental"   ones, though they are more likely, for example, to spoof the Media   Access Control (MAC) or IPv6 source address of the genuine router, or   to use a "High" Router Preference option.  It is also likely that   malicious rogue RAs will be accompanied by other attacks on the IPv6   infrastructure, making discussion of mitigations more complex.   Administrators may be able to detect such activity by the use of   tools such as NDPMon.   It is worth noting that the deprecation daemon could be used as part   of a denial-of-service attack, should the tool be used to deprecate   the genuine RA.8.  Acknowledgments   Thanks are due to members of the IETF IPv6 Operations and DHCP   working groups for their inputs on this topic, as well as some   comments from various operational mailing lists, and private   comments, including but not limited to: Iljitsch van Beijnum, Dale   Carder, Remi Denis-Courmont, Tony Hain, Bob Hinden, Christian   Huitema, Tatuya Jinmei, Eric Levy-Abegnoli, David Malone, Thomas   Narten, Chip Popoviciu, Dave Thaler, Gunter Van de Velde, Goeran   Weinholt, and Dan White.Chown & Venaas                Informational                    [Page 14]

RFC 6104            Rogue IPv6 Router Advertisements       February 20119.  Informative References   [RFC2684]  Grossman, D. and J. Heinanen, "Multiprotocol Encapsulation              over ATM Adaptation Layer 5",RFC 2684, September 1999.   [RFC3056]  Carpenter, B. and K. Moore, "Connection of IPv6 Domains              via IPv4 Clouds",RFC 3056, February 2001.   [RFC3315]  Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,              and M. Carney, "Dynamic Host Configuration Protocol for              IPv6 (DHCPv6)",RFC 3315, July 2003.   [RFC3736]  Droms, R., "Stateless Dynamic Host Configuration Protocol              (DHCP) Service for IPv6",RFC 3736, April 2004.   [RFC3971]  Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure              Neighbor Discovery (SEND)",RFC 3971, March 2005.   [RFC4191]  Draves, R. and D. Thaler, "Default Router Preferences and              More-Specific Routes",RFC 4191, November 2005.   [RFC4192]  Baker, F., Lear, E., and R. Droms, "Procedures for              Renumbering an IPv6 Network without a Flag Day",RFC 4192,              September 2005.   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,              "Neighbor Discovery for IP version 6 (IPv6)",RFC 4861,              September 2007.   [RFC4862]  Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless              Address Autoconfiguration",RFC 4862, September 2007.   [RFC5533]  Nordmark, E. and M. Bagnulo, "Shim6: Level 3 Multihoming              Shim Protocol for IPv6",RFC 5533, June 2009.   [RFC6105]  Levy-Abegnoli, E., Van de Velde, G., Popoviciu, C., and J.              Mohacsi, "IPv6 Router Advertisement Guard",RFC 6105,              February 2011.   [IPv6-AUTOCFG-FILTER]              Ward, N., "IPv6 Autoconfig Filtering on Ethernet              Switches", Work in Progress, March 2009.   [DHCPv6-DEFAULT-RTR]              Droms, R. and T. Narten, "Default Router and Prefix              Advertisement Options for DHCPv6", Work in Progress,              March 2009.Chown & Venaas                Informational                    [Page 15]

RFC 6104            Rogue IPv6 Router Advertisements       February 2011Authors' Addresses   Tim Chown   University of Southampton   Highfield   Southampton, Hampshire  SO17 1BJ   United Kingdom   EMail: tjc@ecs.soton.ac.uk   Stig Venaas   Cisco Systems   Tasman Drive   San Jose, CA  95134   USA   EMail: stig@cisco.comChown & Venaas                Informational                    [Page 16]

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