IPv6 Operations (v6ops) Working Group
Internet Engineering Task Force (IETF) X. Xiao
Internet Draft
Request for Comments: 9898 E. Vasilenko
Intended status:
Category: Informational Huawei Technologies
Expires: Nov. 2025
ISSN: 2070-1721 E. Metz
KPN N.V.
G. Mishra
Verizon Inc.
N. Buraglio
Energy Sciences Network
May 26,
November 2025
Neighbor Discovery Considerations in IPv6 Deployments
draft-ietf-v6ops-nd-considerations-14
Abstract
The Neighbor Discovery (ND) protocol is a critical component of the
IPv6 architecture. The protocol uses multicast in many messages. It
also assumes a security model where all nodes on a link are trusted.
Such a design might be inefficient in some scenarios (e.g., use of
multicast in wireless networks) or when nodes are not trustworthy
(e.g., public access networks). These security and operational
issues and the associated mitigation solutions are documented in more
than 20 twenty RFCs. There is a need to track these issues and
solutions in a single document.
To that aim, this document summarizes the published ND issues and
then describes how all these issues originate from three causes.
Addressing the issues is made simpler by addressing the causes. This
document also analyzes the mitigation solutions and demonstrates that
isolating hosts into different subnets and links can help to address
the three causes. Guidance is provided for selecting a suitable
isolation method to prevent potential ND issues.
Status of this This Memo
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provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents not an Internet Standards Track specification; it is
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(IETF). Note that other groups may also distribute
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received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents valid
approved by the IESG are candidates for a maximum any level of six
months Internet
Standard; see Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be updated, replaced, or obsoleted by other documents obtained at any time. It is inappropriate to use Internet-Drafts as
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This Internet-Draft will expire in Nov. 2025.
https://www.rfc-editor.org/info/rfc9898.
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Table of Contents
1. Introduction...................................................3 Introduction
1.1. Terminology...............................................5 Terminology
2. Review of Inventoried ND Issues................................6 Issues
2.1. Multicast May Cause Performance and Reliability Issues....6 Issues
2.2. Trusting-all-hosts Trusting-All-Hosts May Cause On-link On-Link Security Issues......7 Issues
2.3. Router-NCE-on-Demand May Cause Forwarding Delay, NCE
Exhaustion, and Address Accountability Issues..................7 Issues
2.4. Summary of ND Issues......................................8 Issues
3. Review of ND Mitigation Solutions..............................9 Solutions
3.1. ND Solution in Mobile Broadband IPv6.....................10 IPv6
3.2. ND Solution in Fixed Broadband IPv6......................11 IPv6
3.3. Unique IPv6 Prefix per Host (UPPH).......................12 (UPPH)
3.4. Wireless ND and Subnet ND................................13 ND
3.5. Scalable Address Resolution Protocol.....................14 Protocol
3.6. ARP and ND Optimization for TRILL........................14 TRILL
3.7. Proxy ARP/ND in Ethernet Virtual Private Networks (EVPN).15 (EVPN)
3.8. Reducing Router Advertisements...........................15 Advertisements
3.9. Gratuitous Neighbor Discovery (GRAND)....................15 (GRAND)
3.10. Source Address Validation Improvement (SAVI) and Router
Advertisement Guard...........................................16 Guard
3.11. RFC 6583 Dealing with NCE Exhaustion Attacks............16 Attacks
3.12. Registering Self-generated Self-Generated IPv6 Addresses using DHCPv6..17 Using DHCPv6
3.13. Enhanced DAD............................................17 DAD
3.14. ND Mediation for IP Interworking of Layer 2 VPNs........17 VPNs
3.15. ND Solutions Defined before Before the Latest Versions of ND...17 ND
3.15.1. Secure Neighbor Discovery (SeND)...................18 (SEND)
3.15.2. Cryptographically Generated Addresses (CGA)........18 (CGA)
3.15.3. ND Proxy...........................................18 Proxy
3.15.4. Optimistic DAD.....................................19 DAD
4. Guidelines for Prevention of Potential ND Issues..............19 Issues
4.1. Learning Host Isolation from the Existing Solutions......19 Solutions
4.2. Applicability of Various Isolation Methods...............20 Methods
4.2.1. Applicability of L3+L2 Isolation....................20 Isolation
4.2.2. Applicability of L3 Isolation.......................22 Isolation
4.2.3. Applicability of Partial L2 Isolation...............22 Isolation
4.3. Guidelines for Applying Isolation Methods................23 Methods
5. Security Considerations.......................................24 Considerations
6. IANA Considerations...........................................24 Considerations
7. References....................................................24 References
7.1. Normative References.....................................24 References
7.2. Informative References...................................24
8. Acknowledgments...............................................28 References
Acknowledgements
Authors' Addresses
1. Introduction
Neighbor Discovery (ND) [RFC4861] specifies the mechanisms that IPv6
nodes (hosts and routers) on the same link use to communicate and
learn about each other. Stateless Address Autoconfiguration (SLAAC)
[RFC4862] builds on those ND mechanisms to let nodes configure their
own IPv6 addresses. When analyzing the issues nodes may encounter
with ND, it helps to view the ND messages they exchange throughout
their life-cycle, life cycle, taking SLAAC into consideration.
For a host, the overall procedure is as follows:
1. LLA DAD: The host forms a Link-Local Address (LLA) and performs
Duplicate Address Detection (DAD) using multicast Neighbor
Solicitations (NSs).
2. Router Discovery: discovery: The host sends multicast Router Solicitations
(RSs) to discover a router on the link. The router responds with
Router Advertisements (RAs), providing subnet prefixes and other
information. The host installs a Neighbor Cache Entry (NCE) for
that router upon receiving the RAs. In contrast, the router
cannot install an NCE for the host at this moment of the exchange
because the host's global IP address is still unknown. When the
router later needs to forward a packet to the host's global
address, it will perform address resolution and install an NCE
for the host.
3. GUA DAD: The host forms a Global Unicast Address (GUA) [RFC3587]
or a Unique Local Address (ULA) [RFC4193] and uses multicast NSs
for DAD. For simplicity of description, this document will not
further distinguish GUA and ULA.
4. Next-hop determination and address resolution: When the host
needs to send a packet, it will first determine whether the
next-hop next
hop is a router or an on-link host (which is the destination).
If the next-hop next hop is a router, the host already has the NCE for
that router. If the next-hop next hop is an on-link host, it will use
multicast NSs to perform address resolution for the destination
host. As a result, the source host installs an NCE for the
destination host.
5. Node Unreachability Detection (NUD): The host uses unicast NSs to
determine whether another node with an NCE is still reachable.
6. Link-layer address change announcement: If a host's link-layer
address changes, it may use multicast Node Advertisements (NAs)
to announce its new link-layer address to other nodes.
For a router, the procedure is similar except that there is no
Router Discovery. router
discovery. Instead, routers perform a Redirect procedure that hosts
do not have. A router sends a Redirect to inform a node of a better next-hop
next hop for the node's traffic.
ND uses multicast in many messages, trusts messages from all nodes,
and routers may install NCEs for hosts on demand when they are to
forward packets to these hosts. These may lead to issues.
Concretely, various ND issues and mitigation solutions have been
published in more than 20 RFCs, including:
.
* ND Trust Models and Threats [RFC3756],
. [RFC3756]
* Secure ND [RFC3971],
. [RFC3971]
* Cryptographically Generated Addresses [RFC3972],
. [RFC3972]
* ND Proxy [RFC4389],
. [RFC4389]
* Optimistic ND [RFC4429],
. [RFC4429]
* ND for mobile broadband [RFC6459][RFC7066],
. [RFC6459] [RFC7066]
* ND for fixed broadband [TR177],
. [TR177]
* ND Mediation [RFC6575],
. [RFC6575]
* Operational ND Problems [RFC6583],
. [RFC6583]
* Wireless ND (WiND) [RFC6775][RFC8505][RFC8928][RFC8929][SND],
. [RFC6775] [RFC8505] [RFC8928] [RFC8929] [SND]
* DAD Proxy [RFC6957],
. [RFC6957]
* Source Address Validation Improvement [RFC7039],
. [RFC7039]
* Router Advertisement Guard [RFC6105][RFC7113],
. [RFC6105] [RFC7113]
* Enhanced Duplicate Address Detection [RFC7527],
. [RFC7527]
* Scalable ARP [RFC7586],
. [RFC7586]
* Reducing Router Advertisements [RFC7772],
. [RFC7772]
* Unique Prefix Per Host [RFC8273],
. [RFC8273]
* ND Optimization for Transparent Interconnection of Lots of Links
(TRILL) [RFC8302],
. [RFC8302]
* Gratuitous Neighbor Discovery [RFC9131],
. [RFC9131]
* Proxy ARP/ND for EVPN [RFC9161], and
. [RFC9161]
* Using DHCPv6 Prefix Delegation (DHCPv6-PD) to Allocate Unique IPv6
Prefixes per Client in Large Broadcast Networks [RFC9663]. [RFC9663]
This document summarizes these RFCs into a one-stop reference (as of
the time of writing) for easier access. This document also
identifies three causes of the issues and defines three host
isolation methods to address the causes and prevent potential ND
issues.
1.1. Terminology
This document uses the terms defined in [RFC4861]. Additional terms
are defined in this section.
MAC -
MAC: Media Access Control. To avoid confusion with link-local
addresses, link-layer addresses are referred to as MAC addresses "MAC addresses"
in this document.
Host Isolation - separating isolation: Separating hosts into different subnets or links.
L3 Isolation - allocating Isolation: Allocating a unique prefix Unique Prefix per host
[RFC8273][RFC9663] Host (UPPH) [RFC8273]
[RFC9663] so that every host is in a different subnet. Given that
a unique prefix can be allocated per host on shared media, hosts
in different subnets may be on the same link.
L2 Isolation - taking Isolation: Taking measures to prevent a host from reaching other
hosts directly in Layer 2 (L2) so that every host is in a
different link. Due to the existence of Multi-Link Subnet
[RFC4903], hosts in different links may be in the same subnet.
Therefore, L2 Isolation does not imply L3 Isolation, and L3
Isolation does not imply L2 Isolation either.
L3+L2 Isolation - applying Isolation: Applying L3 Isolation and L2 Isolation
simultaneously so that every host is in a different subnet and on
a different link.
Partial L2 Isolation - using Isolation: Using an L3 ND proxy Proxy [RFC4389] device to
represent the hosts behind it to other hosts in the same subnet.
Within the subnet, ND multicast exchange is segmented into
multiple smaller scopes, each represented by an ND proxy Proxy device.
2. Review of Inventoried ND Issues
2.1. Multicast May Cause Performance and Reliability Issues
In some cases, ND uses multicast for NSs, NAs, RSs, and RAs. While
multicast can be highly efficient in certain scenarios, e.g., scenarios (e.g., in
wired networks, networks), multicast can also be inefficient in other
scenarios, e.g., scenarios
(e.g., in large L2 networks or wireless networks. networks).
Typically, multicast can create a large amount of protocol traffic in
large L2 networks. This can consume network bandwidth, increase
processing overhead, and degrade network performance [RFC7342].
In wireless networks, multicast can be inefficient or even unreliable
due to a higher probability of transmission interference, lower data
rate, and lack of acknowledgements (Section 3.1 of [RFC9119]).
Multicast-related performance issues of the various ND messages are
summarized below:
.
* Issue 1: LLA DAD Degrading Performance - in
In an L2 network of N addresses (which can be much larger than the
number of hosts, as each host can have multiple addresses), there
can be N such multicast messages. This may cause performance
issues when N is large.
.
* Issue 2: Router's Periodic Unsolicited RAs Draining Hosts' Host's Battery - multicast
Multicast RAs are generally limited to one packet every
MIN_DELAY_BETWEEN_RAS (3 seconds), and there are usually only one
or two routers on the link, so it is unlikely to cause a
performance issue. However, for battery-powered hosts, such
messages may wake them up and drain their batteries [RFC7772].
.
* Issue 3: GUA DAD Degrading Performance -
This is the same as in Issue 1.
.
* Issue 4: Router's Address Resolution for Hosts Degrading
Performance -
This is the same as in Issue 1.
.
* Issue 5: Host's Address Resolution for Hosts Degrading Performance -
This is the same as in Issue 1.
. (For Further Study) Hosts'
* Issue for further study: Host's MAC Address Change NAs Degrading
Performance - with
With randomized and changing MAC addresses [MADINAS], there may be
many such multicast messages.
In wireless networks, multicast is more likely to cause packet loss.
Because DAD treats no response as no duplicate address detected,
packet loss may cause duplicate addresses to be undetected.
Multicast reliability issues are summarized below:
.
* Issue 6: LLA DAD Not Completely Reliable in Wireless Networks.
. Networks
* Issue 7: GUA DAD Not Completely Reliable in Wireless Networks. Networks
Note: IPv6 address collisions are extremely unlikely. As a result,
these two issues are largely theoretical rather than practical.
2.2. Trusting-all-hosts Trusting-All-Hosts May Cause On-link On-Link Security Issues
In scenarios such as public access networks, some nodes may not be
trustworthy. An attacker on the link can cause the following on-link
security issues [RFC3756][RFC9099]:
. [RFC3756] [RFC9099]:
* Issue 8: Source IP Address Spoofing - an
An attacker can use another node's IP address as the source
address of its ND message to pretend to be that node. The
attacker can then launch various Redirect or Denial-of-Service
(DoS) attacks.
.
* Issue 9: Denial of DAD - an
An attacker can repeatedly reply to a victim's DAD messages,
causing the victim's address configuration procedure to fail,
resulting in a DoS to the victim.
.
* Issue 10: Rogue RAs - an
An attacker can send RAs to victim hosts to pretend to be a
router. The attacker can then launch various Redirect or DoS
attacks.
.
* Issue 11: Spoofed Redirects - an
An attacker can send forged Redirects to victim hosts to redirect
their traffic to the legitimate router itself.
.
* Issue 12: Replay Attacks - an
An attacker can capture valid ND messages and replay them later.
2.3. Router-NCE-on-Demand May Cause Forwarding Delay, NCE Exhaustion,
and Address Accountability Issues
When a router needs to forward a packet to a node but does not yet
have a Neighbor-Cache Entry (NCE) for that node, it first creates an
NCE in the INCOMPLETE state. The router then multicasts an NS to the
node's solicited-node multicast address. When the destination
replies with an NA containing its MAC address, the router updates the
NCE with that address and changes its state to REACHABLE, thereby
completing the entry. This process is referred to as Router-
NCE-on-Demand
"Router-NCE-on-Demand" in this document.
Router-NCE-on-Demand can cause the following issues:
.
* Issue 13: NCE Exhaustion - an
An attacker can send a high volume of packets targeting non-existent non-
existent IP addresses, causing the router to create numerous NCEs
in the INCOMPLETE state. The resulting resource exhaustion may
cause the router to malfunction. This vulnerability, described as
"NCE Exhaustion" in this document, does not require the attacker
to be on-link.
.
* Issue 14: Router Forwarding Delay - when
When a packet arrives at a router, the router buffers it while
attempting to determine the host's MAC address. This buffering
delays forwarding and, depending on the router's buffer size, may
lead to packet loss. This delay is referred to as
"Router-NCE-on-Demand Forwarding Delay" in this document.
.
* Issue 15: Lack of Address Accountability - with
With SLAAC, hosts generate their IP addresses. The router does
not become aware of a host's IP address until an NCE entry is
created. With DHCPv6 [RFC8415], the router may not know the
host's addresses unless it performs DHCPv6 snooping. In public
access networks, where subscriber management often relies on IP
address (or prefix) identification, this lack of address
accountability poses a challenge [AddrAcc]. Without knowledge of
the host's IP address, network administrators are unable to
effectively manage subscribers, which is particularly problematic
in public access networks. Moreover, once a router has created
its NCEs, ND [RFC4861] provides no mechanism to retrieve them for
management or monitoring, as noted in Section 2.6.1 of [RFC
9099]. [RFC9099].
2.4. Summary of ND Issues
The ND issues, as discussed in Sections 2.1 to 2.1, 2.2, and 2.3, are
summarized below. These issues stem from three primary causes:
multicast, Trusting-all-nodes, and Router-NCE-on-Demand. Eliminating
any of these causes would also mitigate the corresponding issues.
These observations provide guidance for addressing and preventing ND-
related issues.
(1)
1. Multicast-related issues:
.
* Performance issues
o issues:
- Issue 1: LLA DAD Degrading Performance.
o Performance
- Issue 2: Unsolicited RA Draining Host Battery Life.
o Life
- Issue 3: GUA DAD degrading performance.
o performance
- Issue 4: Router Address Resolution for Hosts Degrading
Performance.
o
Performance
- Issue 5: Host Address Resolution for Other Hosts Degrading
Performance.
.
Performance
* Reliability issues
o issues:
- Issue 6: LLA DAD Not Completely Reliable in Wireless
Networks
o
- Issue 7: GUA DAD Not Completely Reliable in Wireless
Networks
(2)
2. Trusting-all-nodes related issues:
o
* Issue 8: Source IP Address Spoofing
o
* Issue 9: Denial of DAD
o
* Issue 10: Rogue RAs
o
* Issue 11: Spoofed Redirects
o
* Issue 12: Replay Attacks
(3)
3. Router-NCE-on-Demand related issues:
o
* Issue 13: NCE Exhaustion
o
* Issue 14: Router Forwarding Delay
o
* Issue 15: Lack of Address Accountability
These issues are potential vulnerabilities and may not manifest in
all usage scenarios.
When these issues may occur in a specific deployment, it is advisable
to consider the mitigation solutions available. They are described
in the following section.
3. Review of ND Mitigation Solutions
Table 1 summarizes ND mitigation solutions available for Issues 1-15
described in Section 2.4. Similar solutions are grouped, beginning
with those that address the most issues. Unrelated solutions are
ordered based on the issues (listed in Section 2.4) they address.
Each solution in the table will be explained in a sub-section later,
where abbreviations in the table are described.
In the table, Table 1, a letter code indicates the RFC category of the
mitigation solution (see BCP 9 [RFC2026] for an explanation of these
categories):
S -
S: Standards Track (Proposed Standard, Draft Standard, or Internet
Standard)
E -
E: Experimental
I -
I: Informational
B -
B: Best Current Practice
U - Unknown
N/A: Not Applicable (not formally defined by the IETF)
+-----+---+-------------------+--------+-------+-------+------+-----+
|ND |RFC| Multicast an RFC)
+==========+====+===========+=======+=========+====+=======+=======+
| Reli- |On-link|NCE |Fwd. |No A.|
|solu-|ty-| performance ND |RFC |Multicast |Reliabi| On-link |NCE | ability|securi.|Exhau. |Delay |Acct.|
|tion |pe |---+---+---+---+---+---+----+-------+-------+------+-----+ Fwd. | No |
| 1 solution |cat.|performance|lity | 2 sec. |Exh.| Delay | 3 Addr. | 4
| 5 | 6 | 7 | | | | | Acc. |
| | +===+=+=+=+=+=====+=+=========+====+=======+=======+
| | | 1 |2|3|4|5| 6 |7| 8-12 | 13 | 14 | 15 |
+-----+---+---+---+---+---+---+---+----+-------+-------+------+-----+
|MBBv6|
+==========+====+===+=+=+=+=+=====+=+=========+====+=======+=======+
| MBBv6 | I | All identified issues solved |
+-----+---+---+---+---+---+---+---+----+-------+-------+------+-----+
|FBBv6| U
+----------+----+--------------------------------------------------+
| FBBv6 |N/A | All identified issues solved |
+-----+---+---+---+---+---+---+---+----+-------+-------+------+-----+
|UPPH | I
+----------+----+---+-+-+-+-+-----+-+---------+----+-------+-------+
| UPPH | X | | X | X I | |X| |X|X| |X| | X | | X | X | X
+----------+----+---+-+-+-+-+-----+-+---------+----+-------+-------+
|
+-----+---+---+---+---+---+---+---+----+-------+-------+------+-----+
|WiND WiND | S |All issues solved for Low-Power and Lossy Networks (LLNs)|
+-----+---+---+---+---+---+---+---+----+-------+-------+------+-----+
|SARP | E | | | | | X | | | | | | |
+-----+---+---+---+---+---+---+---+----+-------+-------+------+-----+
|ND | S | | | | | X | | Networks|
| | | (LLNs) |
+----------+----+---+-+-+-+-+-----+-+---------+----+-------+-------+
|
|TRILL| SARP | E | | | | |X| | | | | | |
+----------+----+---+-+-+-+-+-----+-+---------+----+-------+-------+
|
+-----+---+---+---+---+---+---+---+----+-------+-------+------+-----+
|ND ND TRILL | S | | | | | X | |X| | | | | | |
|EVPN
+----------+----+---+-+-+-+-+-----+-+---------+----+-------+-------+
| ND EVPN | S | | | | |X| | | | | | |
+----------+----+---+-+-+-+-+-----+-+---------+----+-------+-------+
|
+-----+---+---+---+---+---+---+---+----+-------+-------+------+-----+
|7772 7772 | B | |X| | X | | | | | | | |
+----------+----+---+-+-+-+-+-----+-+---------+----+-------+-------+
| GRAND |
+-----+---+---+---+---+---+---+---+----+-------+-------+------+-----+
|GRAND| S | | | | X | |X| | | | | | X | |
+-----+---+---+---+---+---+---+---+----+-------+-------+------+-----+
|SAVI/| | | | | |
+----------+----+---+-+-+-+-+-----+-+---------+----+-------+-------+
| | | | | | |
|RA SAVI/RA | I | | | | | | | | X | | | |
|G/G+
| G/G+ | | | | | | | | | | | | |
+-----+---+---+---+---+---+---+---+----+-------+-------+------+-----+
|6583
+----------+----+---+-+-+-+-+-----+-+---------+----+-------+-------+
| 6583 | I | | | | | | | | | X | | |
+-----+---+---+---+---+---+---+---+----+-------+-------+------+-----+
|9686
+----------+----+---+-+-+-+-+-----+-+---------+----+-------+-------+
| 9686 | S | | | | | | | | | | | X |
+-----+---+---+---+---+---+---+---+----+-------+-------+------+-----+
+----------+----+---+-+-+-+-+-----+-+---------+----+-------+-------+
Table 1. 1: Solutions for identified issues Identified Issues
3.1. ND Solution in Mobile Broadband IPv6
The IPv6 solution defined in "IPv6 in 3GPP EPS" 3rd Generation Partnership
Project (3GPP) Evolved Packet System (EPS)" [RFC6459], "IPv6 for
3GPP
Third Generation Partnership Project (3GPP) Cellular Hosts"
[RFC7066], and "Extending an IPv6 /64 Prefix from a Third Generation
Partnership Project (3GPP) Mobile Interface to a LAN Link" [RFC7278]
is called Mobile Broadband IPv6 (MBBv6) in this document. They are
Informational RFCs. The key points are:
.
* Putting every host, e.g., host (e.g., the mobile User Equipment (UE), (UE)) in a
Point-to-Point (P2P) link with the router, e.g., router (e.g., the mobile
gateway. Consequently:
o
gateway) has the following outcomes:
- All multicast is effectively turned into unicast.
o
- The P2P links do not have a MAC address. Therefore, Router-
NCE-on-Demand is not needed.
o
- Trusting-all-nodes is only relevant to the router. By applying
filtering at the router, e.g., router (e.g., dropping RAs from the hosts, hosts),
even malicious hosts cannot cause harm.
.
* Assigning a unique /64 prefix to each host. Together with the P2P
link, this puts each host on a separate link and subnet.
.
* Maintaining (prefix, interface) binding at the router for
forwarding purposes.
Since all the three causes of ND issues are addressed, all the issues
discussed in Section 2.4 are addressed.
3.2. ND Solution in Fixed Broadband IPv6
The IPv6 solution defined in "IPv6 in the context of TR-101" [TR177]
is called Fixed Broadband IPv6 (FBBv6) in this document. FBBv6 has
two flavors:
.
* P2P: Every host, e.g., host (e.g., the Residential Gateway (RG), (RG)) is in a P2P
link with the router, e.g., router (e.g., the Broadband Network Gateway
(BNG). (BNG)).
In this case, the solution is functionally similar to MBBv6. All
ND issues discussed in Section 2.4 are solved.
. Point-to-Multi-Point
* Point to Multipoint (P2MP): All hosts, e.g., hosts (e.g., the RGs, RGs) connected to
an access device, e.g., device (e.g., the Optical Line Terminal
(OLT), (OLT)) are in a
P2MP link with the router, e.g., router (e.g., the BNG. BNG). This is achieved by
placing all hosts in a single VLAN on the router and configuring
the OLT to block any frame from being forwarded between its access
ports; traffic from each host can travel only up toward the
router, not sideways to another host, thereby preventing direct
host-to-host communication.
The following list summarizes the two key aspects of the FBBv6-P2MP
architecture as described in [TR177] and the associated benefits:
.
* Implementing DAD Proxy proxy [RFC6957]:
In a P2MP architecture described above, the normal ND DAD
procedure will breaks break down because hosts cannot exchange NSs with
one another. To address this, the router participates in the DAD
process as a DAD Proxy to resolve address duplication.
The benefits are:
o
- Multicast traffic from all hosts to the router is effectively
converted into unicast, as hosts can only communicate directly
with the router.
o
- The Trusting-all-nodes model is limited to the router. By
applying simple filtering, e.g., filtering (e.g., dropping RAs from hosts, hosts), the
router can mitigate security risks, even from malicious hosts
. hosts.
* Assigning a unique /64 prefix to each host:
Assigning each host a unique /64 prefix results in several
operational improvements:
o
- The router can proactively install a forwarding entry for that
prefix towards the host, eliminating the need for
Router-NCE-on-Demand.
o Router-NCE-
on-Demand.
- Since each host resides in a different subnet, traffic between
hosts is routed through the router, eliminating the need for
hosts to perform address resolution for one another.
o
- Without address resolution, router multicast to hosts is
limited to unsolicited RAs. As each host resides in its own
subnet, these RAs are sent as unicast packets to individual
hosts. This follows the approach specified in [RFC6085], where
the host's MAC address replaces the multicast MAC address in
the RA.
Since all three causes of ND issues are addressed, all ND issues
(Section 2.4) are also addressed.
3.3. Unique IPv6 Prefix per Host (UPPH)
UPPH
Unique IPv6 Prefix per Host (UPPH) solutions are described in
[RFC8273] and [RFC9663]. Both are Informational RFCs. [RFC8273]
relies on SLAAC for unique prefix allocation while [RFC9663] relies
on DHCP-PD. DHCPv6 Prefix Delegation (DHCPv6-PD). That difference in
allocation mechanism does not change the discussion on ND issues,
because every IPv6 node is still required to run SLAAC, even when it
receives its prefix via DHCP-PD. DHCPv6-PD. Therefore, discussing [RFC8273]
alone is sufficient.
[RFC8273] "improves host isolation and enhanced subscriber management
on shared network segments" such as Wi-Fi or Ethernet. The key
points are:
.
* When a prefix is allocated to the host, the router can proactively
install a forwarding entry for that prefix towards the host.
There is no more Router-NCE-on-Demand.
.
* Without address resolution, router multicast to hosts consists
only of unsolicited RAs. They will be sent to hosts one by one in
unicast because the prefix for every host is different.
.
* Since different hosts are in different subnets, hosts will send
traffic to other hosts via the router. There is no host-to-host
address resolution.
Therefore, ND issues caused by Router-NCE-on-Demand and router
multicast to hosts are prevented.
[RFC8273] indicates that a "network implementing a unique IPv6 prefix
per host can simply ensure that devices cannot send packets to each
other except through the first-hop router". But However, when hosts are
on a shared medium like Ethernet, ensuring "devices cannot send
packets to each other except through the first-hop router" requires
additional measures like Private VLAN [RFC5517]. Without such
additional measures, on a shared medium, hosts can still reach each
other in L2 as they belong to the same Solicited-Node Multicast
Group. Therefore, Trusting-all-nodes and host multicast to routers
may cause issues. Of the host multicast issues (i.e., Issues 1, 3,
5, 6, and 7), Unique Prefix per Host UPPH prevents Issues 5 and 7, because there is no need
for address resolution among hosts (Issue
5) 5), and there is no
possibility of GUA duplication (Issue 7). But However, Issues 1, 3, and
6 may occur.
3.4. Wireless ND and Subnet ND
Wireless ND (WiND) [RFC6775][RFC8505][RFC8928][RFC8929] [RFC6775] [RFC8505] [RFC8928] [RFC8929] (Standards
Track) defines a fundamentally different ND solution for Low-Power
and Lossy Networks (LLNs) [RFC7102]. WiND changes host and router
behaviors to use multicast only for router discovery. The key points
are:
.
* Hosts use unicast to proactively register their addresses at the
routers. Routers use unicast to communicate with hosts and become
an abstract registrar and arbitrator for address ownership.
.
* The router also proactively installs NCEs for the hosts. This
avoids the need for address resolution for the hosts.
.
* The router sets the Prefix Information Option (PIO) L-bit to 0.
Each host communicates only with the router (Section 6.3.4 of
[RFC4861]).
.
* Other functionalities that are relevant only to LLNs.
WiND addresses all ND issues (Section 2.4) in LLNs. However, WiND
support is not mandatory for general-purpose hosts. Therefore, it
cannot be relied upon as a deployment option without imposing
additional constraints on the participating nodes.
3.5. Scalable Address Resolution Protocol
The Scalable Address Resolution Protocol (SARP) [RFC7586] was an
Experimental solution. That experiment ended in 2017, two years
after the RFC was published. Because the idea has been used in
mitigation solutions for more specific scenarios (described in
Sections 3.6 and 3.7), it is worth describing here. The usage
scenario is Data Centers (DCs), where large L2 domains span across
multiple sites. In each site, multiple hosts are connected to a
switch. The hosts can be Virtual Machines (VMs), so the number can
be large. The switches are interconnected by a native or overlay L2
network.
The switch will snoop and install a (IP, MAC address) proxy table for
the local hosts. The switch will also reply to address resolution
requests from other sites to its hosts with its own MAC address. In
doing so, all hosts within a site will appear to have a single MAC
address to other sites. As such, a switch only needs to build a MAC
address table for the local hosts and the remote switches, not for
all the hosts in the L2 domain. Consequently, the MAC address table
size of the switches is significantly reduced. A switch will also
add the (IP, MAC address) replies from remote switches to its proxy
ND table so that it can reply to future address resolution requests
from local hosts for such IPs directly. This greatly reduces the
number of address resolution multicast in the network.
Unlike MBBv6, FBBv6, and UPPH, which try to address all ND issues
discussed in Section 2.4, SARP focuses on reducing address resolution
multicast to improve the performance and scalability of large L2
domains in DCs.
3.6. ARP and ND Optimization for TRILL
ARP and ND Optimization optimization for TRILL Transparent Interconnection of Lots of
Links (TRILL) [RFC8302] (Standards Track) is similar to SARP
(Section 3.5). It can be considered an application of SARP in the
TRILL environment.
Like SARP, ARP, and ND Optimization optimization for TRILL focuses on reducing
multicast address resolution. That is, it addresses Issue 5
(Section 2.1).
3.7. Proxy ARP/ND in Ethernet Virtual Private Networks (EVPN)
Proxy ARP/ND in EVPN is specified in [RFC9161] (Standards Track).
The usage scenario is DCs where large L2 domains span across multiple
sites. In each site, multiple hosts are connected to a Provider Edge
(PE) router. The PEs are interconnected by EVPN tunnels.
The PE of each site snoops the local address resolution NAs to build
(IP, MAC address) Proxy ND table entries. PEs then propagate such
Proxy ND entries to other PEs via the Border Gateway Protocol (BGP).
Each PE also snoops local hosts' address resolution NSs for remote
hosts. If an entry exists in its Proxy ND table for the remote
hosts, the PE will reply directly. Consequently, the number of
multicast address resolution messages is significantly reduced.
Like SARP, Proxy ARP/ND in EVPN also focuses on reducing address
resolution multicast.
3.8. Reducing Router Advertisements
Maintaining IPv6 connectivity requires that hosts be able to receive
periodic multicast RAs [RFC4861]. Hosts that process unicast packets
while they are asleep must also process multicast RAs while they are
asleep. An excessive number of RAs can significantly reduce the
battery life of mobile hosts. [RFC7772] (Best Current Practice)
specifies a solution to reduce RAs:
.
* The router should respond to RS with unicast RA (rather than the
normal multicast RA) if the host's source IP address is specified
and the host's MAC address is valid. This way, other hosts will
not receive this RA.
.
* The router should reduce the multicast RA frequency frequency.
[RFC7772] addresses Issue 2 (Section 2.1).
3.9. Gratuitous Neighbor Discovery (GRAND)
GRAND [RFC9131] (Standards Track) changes ND in the following ways:
.
* A node sends unsolicited NAs upon assigning a new IPv6 address to
its interface.
.
* A router creates a new NCE for the node and sets its state to
STALE.
When a packet for the host later arrives, the router can use the
existing STALE NCE to forward it immediately ([RFC4861] ([RFC4861],
Section 7.2.2). It then verifies reachability by sending a unicast
NS rather than a multicast one for address resolution. In this way,
GRAND eliminates the Router Forwarding Delay. But Delay, but it does not solve
other Router-NCE-on-Demand issues. For example, NCE Exhaustion can
still happen.
3.10. Source Address Validation Improvement (SAVI) and Router
Advertisement Guard
SAVI
Source Address Validation Improvement (SAVI) [RFC7039]
(Informational) binds an address to a port on an L2 switch and
rejects claims from other ports for that address. Therefore, a node
cannot spoof the IP address of another node.
Router Advertisement Guard (RA-Guard) [RFC6105][RFC7113] [RFC6105] [RFC7113]
(Informational) only allows RAs from a port that a router is
connected to. Therefore, nodes on other ports cannot pretend to be a
router.
SAVI and RA-Guard address the on-link security issues.
3.11. RFC 6583 Dealing with NCE Exhaustion Attacks
[RFC6583] (Informational) deals with the NCE Exhaustion attack issue
(Section 2.3). It recommends that:
.
* Operators should
o should:
- Filter unused address space so that messages to such addresses
can be dropped rather than triggering NCE creation.
o
- Implement rate-limiting mechanisms for ND message processing to
prevent CPU and memory resources from being overwhelmed.
.
* Vendors should
o Prioritizing should:
- Prioritize NDP processing for existing NCEs over creating new NCEs
NCEs.
[RFC6583] acknowledges that "some of these options are 'kludges', and
can be operationally difficult to manage". [RFC6583] partially
addresses the Router NCE Exhaustion issue. In practice, router
vendors cap the number of NCEs per interface to prevent cache
exhaustion. If the link has more addresses than that cap, the router
cannot keep an entry for every address, and packets destined for
addresses without an NCE are simply dropped [RFC9663].
3.12. Registering Self-generated Self-Generated IPv6 Addresses using Using DHCPv6
In IPv4, network administrators can retrieve a host's IP address from
the DHCP server and use it for subscriber management. In IPv6 and
SLAAC, this is not possible (Section 2.3).
[RFC9686] (Standards Track) defines a method for informing a DHCPv6
server that a host has one or more self-generated or statically
configured addresses. This enables network administrators to
retrieve the IPv6 addresses for each host from the DHCPv6 server.
[RFC9686] provides a solution for Issue 15 (Section 2.3).
3.13. Enhanced DAD
Enhanced DAD [RFC7527] (Standards Track) addresses a DAD failure
issue in a specific situation: a looped back looped-back interface. DAD will
fail in a looped-back interface because the sending host will receive
the DAD message back and will interpret it as another host is trying
to use the same address. The solution is to include a Nonce option
[RFC3971] in each DAD message so that the sending host can detect
that the looped-back DAD message is sent by itself.
Enhanced DAD does not solve any ND issue. It extends ND to work in a
new scenario: a looped-back interface. It is reviewed here only for
completeness.
3.14. ND Mediation for IP Interworking of Layer 2 VPNs
ND mediation is specified in [RFC6575] (Standards Track). When two
Attachment Circuits (ACs) are interconnected by a Virtual Private
Wired Service (VPWS), and the two ACs are of different media (e.g.,
one is Ethernet while the other is Frame Relay), the two PEs must
interwork to provide mediation service so that a Customer Edge (CE)
can resolve the MAC address of the remote end. [RFC6575] specifies
such a solution.
ND Mediation mediation does not address any ND issue. It extends ND to work in
a new scenario: two ACs of different media interconnected by a VPWS.
It is reviewed here only for completeness.
3.15. ND Solutions Defined before Before the Latest Versions of ND
The latest versions of ND and SLAAC are specified in [RFC4861] and
[RFC4862]. Several ND mitigation solutions were published before
[RFC4861]. They are reviewed in this section only for completeness.
3.15.1. Secure Neighbor Discovery (SeND) (SEND)
The purpose of SeND SEND [RFC3971] (Standards Track) is to ensure that
hosts and routers are trustworthy. SeND SEND defined three new ND
options, i.e., Cryptographically Generated Addresses (CGA) [RFC3972]
(Standards Track), RSA public-key cryptosystem, and Timestamp/Nonce,
an authorization delegation discovery process, an address ownership
proof mechanism, and requirements for the use of these components in
the ND protocol.
3.15.2. Cryptographically Generated Addresses (CGA)
The purpose of CGA is to associate a cryptographic public key with an
IPv6 address in the SeND SEND protocol. The key point is to generate the
Interface Identifier (IID) of an IPv6 address by computing a
cryptographic hash of the public key. The resulting IPv6 address is
called a CGA. The corresponding private key can then be used to sign
messages sent from the address.
CGA assumes that a legitimate host does not care about the bit
combination of the IID that would be created by some hash procedure.
The attacker needs an exact IID to impersonate the legitimate hosts,
but then the attacker is challenged to do a reverse hash calculation calculation,
which is a strong mathematical challenge.
CGA is part of SeND. SEND. There is no reported deployment.
3.15.3. ND Proxy
ND Proxy [RFC4389] (Experimental) aims to enable multiple links
joined by an ND Proxy device to work as a single link.
.
* When an ND Proxy receives an ND request from a host on a link, it
will proxy the message out the "best" (defined in the next
paragraph) outgoing interface. If there is no best interface, the
ND Proxy will proxy the message to all other links. Here, proxy
means acting as if the ND message originates from the ND Proxy
itself. That is, the ND Proxy will change the ND message's source
IP and source MAC address to the ND Proxy's outgoing interface's
IP and MAC address, and create an NCE entry at the outgoing
interface accordingly.
.
* When ND Proxy receives an ND reply, it will act as if the ND
message is destined for itself, and update the NCE entry state at
the receiving interface. Based on such state information, the ND
Proxy can determine the "best" outgoing interface for future ND
requests. The ND Proxy then proxies the ND message back to the
requesting host.
ND Proxy is widely used in SARP (Sections (Section 3.5), ND Optimization optimization for
TRILL (Sections (Section 3.6), and Proxy ARP/ND in EVPN (Sections (Section 3.7).
3.15.4. Optimistic DAD
Optimistic DAD [RFC4429] (Standards Track) seeks to minimize address
configuration delays in the successful case and to reduce disruption
as far as possible in the failure case. That is, Optimistic DAD lets
hosts immediately use the newly formed address to communicate before
DAD completes, assuming that DAD will succeed anyway. If the address
turns out to be duplicate, Optimistic DAD provides a set of
mechanisms to minimize the impact. Optimistic DAD modified the
original ND [RFC2461] and original SLAAC [RFC2462], [RFC2462] (both of which are
obsolete), but the solution was not incorporated into the latest
specifications of ND [RFC4861] and SLAAC [RFC4862]. However,
implementations of Optimistic DAD exist.
Optimistic DAD does not solve any ND issue (Section 2). It is
reviewed here only for completeness.
4. Guidelines for Prevention of Potential ND Issues
By knowing the potential ND issues and associated mitigation
solutions, network administrators of existing IPv6 deployments can
assess whether these issues may occur in their networks and, if so,
whether to deploy the mitigation solutions proactively. Deploying
these solutions may take time and additional resources. Therefore,
it is advisable to plan.
Network administrators planning to start their IPv6 deployments can
use the issue-solution information to help plan their deployments.
Moreover, they can take proactive action to prevent potential ND
issues.
4.1. Learning Host Isolation from the Existing Solutions
While various ND solutions may initially appear unrelated,
categorizing them into four distinct groups highlights an important
observation: "host isolation" host isolation is an effective strategy for mitigating
ND-related issues.
* Group 1: L3 and L2 Isolation
This group includes MBBv6 and FBBv6, which isolate hosts at both
L3 and L2 by placing each host within its subnet and link. This
prevents ND issues caused by multicast and Trusting-all-nodes, as
each host operates within its isolated domain. Furthermore, since
routers can route packets to a host based on its unique prefix,
the need for Router-NCE-on-Demand is also eliminated. Therefore,
L3 and L2 Isolation prevent all ND issues.
* Group 2: L3 Isolation
This group includes UPPH solutions like [RFC8273] and [RFC9663],
which isolate hosts into separate subnets while potentially
leaving them on the same shared medium. This approach mitigates
ND issues caused by router multicast to hosts and eliminates the
need for
"Router-NCE-on-Demand", Router-NCE-on-Demand, as detailed in Section 3.3.
* Group 3: Partial L2 Isolation
This group encompasses solutions such as WiND, SARP, ND Optimization
optimization for TRILL, and Proxy ND in EVPN. These solutions use
a proxy device to represent the hosts behind it, effectively
isolating those hosts into distinct multicast domains. While
hosts are still located within the same subnet, their separation
into different multicast domains reduces the scope of ND issues
related to multicast-based address resolution.
* Group 4: Non-Isolating Solutions
The final group includes remaining solutions that do not implement
host isolation. These solutions do not prevent ND issues but
instead focus on addressing specific ND problems.
The analysis demonstrates that the stronger the isolation of hosts,
the more ND issues can be mitigated. This correlation is intuitive,
as isolating hosts reduces the multicast scope, minimizes the number
of nodes that must be trusted, and may eliminate the need for
"Router-NCE-on-Demand", Router-
NCE-on-Demand, the three primary causes of ND issues.
This understanding can be used to prevent ND issues.
4.2. Applicability of Various Isolation Methods
4.2.1. Applicability of L3+L2 Isolation
Benefits:
o
* All ND issues (Section 2.4) can be effectively mitigated.
Constraints:
1. L2 Isolation:
Actions must be taken to isolate hosts in L2. The required
effort varies by the chosen method and deployment context. For
example, the P2P method [RFC7066] is heavy-weight, heavyweight, while the
Private VLAN method [RFC5517] is more manageable.
2. Unique Prefix Allocation:
A large number of prefixes will be required, with one prefix
assigned per host. This is generally not a limitation for IPv6.
For instance, members of a Regional Internet Registry (RIR) can
obtain a /29 prefix allocation [RIPE738], which provides 32
billion /64 prefixes - -- sufficient for any foreseeable deployment
scenarios. Practical implementations, such as MBBv6 assigning
/64 prefixes to billions of mobile UEs [RFC6459] [RFC6459], and FBBv6
assigning /56 prefixes to hundreds of millions of routed RGs
[TR177], demonstrate the feasibility of this approach.
3. Privacy Issue from Unique Prefix Identifiability:
Assigning a unique prefix to each host may theoretically reduce
privacy, as hosts can be directly identified by their assigned
prefix. However, alternative host identification methods, such
as cookies, are commonly used. Therefore, unique prefix
identifiability may not make much difference. The actual impact
on privacy is therefore likely to be limited.
4. Router Support for L3 Isolation:
The router must support an L3 Isolation solution, e.g., [RFC8273]
or [RFC9663].
5. A Large Number of Router Interfaces May be Needed:
If the P2P method is used, the router must instantiate a separate
logical interface for every attached host. In this case, a large
number of interfaces will be needed at the router.
6. Router as a Bottleneck:
Since all communication between hosts is routed through the
router, the router may become a performance bottleneck in high-traffic high-
traffic scenarios.
7. Incompatibility with Host-Based Multicast Services:
Services that rely on multicast communication among hosts, such
as the Multicast Domain Name System [RFC6762], will be disrupted.
4.2.2. Applicability of L3 Isolation
Benefits:
.
* All ND issues (Section 2.4) are mitigated, with the exception of:
o
- LLA DAD multicast degrading performance,
o
- LLA DAD not reliable in wireless networks, and
o On-link security
- on-link security.
These remaining issues depend on the characteristics of the shared
medium:
o
- If the shared medium is Ethernet, the issues related to LLA DAD
multicast are negligible.
o
- If nodes can be trusted, such as in private networks, on-
link on-link
security concerns are not significant.
. No
* There is no need for L2 Isolation. Consequently, this method can
be applied in a wide range of scenarios, making it possibly the
most practical host isolation method.
Constraints, as
Constraints (as discussed in Section 4.2.1: 4.2.1):
1. Unique Prefix Allocation
2. Router Support for L3 Isolation
3. Router as a Bottleneck
4. Privacy Issue from Unique Prefix Identifiability.
4.2.3. Applicability of Partial L2 Isolation
Benefits:
.
Benefit:
* Reduced Multicast Traffic: This method reduces multicast traffic,
particularly for address resolution, by dividing the subnet into
multiple multicast domains.
Constraint:
.
* Router Support for Partial L2 Isolation: The router must implement
a Partial L2 Isolation solution such as WiND, SARP, ND Optimization
optimization for TRILL, and Proxy ND in EVPN to support this
method.
4.3. Guidelines for Applying Isolation Methods
Based on the applicability analysis provided in the preceding
sections, network administrators can determine whether to implement
an isolation method and, if so, which method is most appropriate for
their specific deployment.
A simple guideline is to consider the isolation methods in the order
listed in the preceding sections, progressing from the strongest
isolation to the weakest:
.
* Stronger isolation methods can prevent more ND issues, but may
also impose higher entry requirements.
.
* Weaker isolation methods have fewer entry requirements but may
leave some ND issues unmitigated.
The choice between L3+L2 Isolation and L3 Isolation often depends on
the cost of implementing L2 Isolation:
.
* If the cost is acceptable, L3+L2 Isolation is preferable because
it eliminates every ND issue listed in Section 2.4.
.
* Otherwise, L3 Isolation addresses most of those issues while
keeping the implementation effort reasonable.
Selecting an isolation method that is either too strong or too weak
does not result in serious consequences:
.
* Choosing an overly strong isolation method may require the network
administrator to meet higher entry requirements initially, such as
measures for L2 Isolation, additional prefixes, or additional
router capabilities.
.
* Choosing a "weaker weaker isolation method" method may necessitate deploying
supplemental ND mitigation techniques to address any unresolved ND
issues.
In either case, the resulting solution can be functional and
effective.
5. Security Considerations
This document is a review of known ND issues and solutions, including
security. It does not introduce any new solutions. Therefore, it
does not introduce new security issues.
6. IANA Considerations
This document has no request to IANA. IANA actions.
7. References
7.1. Normative References
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861. 4861,
DOI 10.17487/RFC4861, September 2007,
<https://www.rfc-editor.org/info/rfc4861>.
[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", RFC 4862. 4862,
DOI 10.17487/RFC4862, September 2007,
<https://www.rfc-editor.org/info/rfc4862>.
7.2. Informative References
[AddrAcc] T. Chown, C. T., Cummings, D.Carder, C., and D. W. Carder, "IPv6 Address
Accountability Considerations", Internet draft, Oct. 2024. Work in Progress,
Internet-Draft, draft-ccc-v6ops-address-accountability-00,
21 October 2024, <https://datatracker.ietf.org/doc/html/
draft-ccc-v6ops-address-accountability-00>.
[MADINAS] J. Henry, J. and Y. Lee, "Randomized and Changing MAC Address: Media
Access Control (MAC) Addresses: Context, Network Impacts,
and Use Cases", draft-ietf-
madinas-use-cases-19. RFC 9797, DOI 10.17487/RFC9797, June 2025,
<https://www.rfc-editor.org/info/rfc9797>.
[RFC2026] S. Bradner, S., "The Internet Standards Process -- Revision
3", BCP 9, RFC 2026. 2026, DOI 10.17487/RFC2026, October 1996,
<https://www.rfc-editor.org/info/rfc2026>.
[RFC2461] T. Narten, E. T., Nordmark, E., and W. Simpson, "Neighbor
Discovery for IP Version 6 (IPv6)", RFC 2461, obsoleted by RFC 4861.
DOI 10.17487/RFC2461, December 1998,
<https://www.rfc-editor.org/info/rfc2461>.
[RFC2462] S. Thomson, S. and T. Narten, "IPv6 Stateless Address
Autoconfiguration", RFC 2462, obsoleted by RFC 4862. DOI 10.17487/RFC2462,
December 1998, <https://www.rfc-editor.org/info/rfc2462>.
[RFC3587] R. Hinden, S. R., Deering, S., and E. Nordmark, "IPv6 Global
Unicast Address Format", RFC 3587. 3587, DOI 10.17487/RFC3587,
August 2003, <https://www.rfc-editor.org/info/rfc3587>.
[RFC3756] P. Nikander, J. P., Ed., Kempf, J., and E. Nordmark, "IPv6
Neighbor Discovery (ND) Trust Models and Threats",
RFC 3756. 3756, DOI 10.17487/RFC3756, May 2004,
<https://www.rfc-editor.org/info/rfc3756>.
[RFC3971] J. Arkko, J. J., Ed., Kempf, B. J., Zill, B., and P. Nikander,
"SEcure Neighbor Discovery (SEND)", RFC3971. RFC 3971,
DOI 10.17487/RFC3971, March 2005,
<https://www.rfc-editor.org/info/rfc3971>.
[RFC3972] T. Aura, T., "Cryptographically Generated Addresses (CGA)",
RFC3972.
RFC 3972, DOI 10.17487/RFC3972, March 2005,
<https://www.rfc-editor.org/info/rfc3972>.
[RFC4193] R. Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
Addresses", RFC 4193. 4193, DOI 10.17487/RFC4193, October 2005,
<https://www.rfc-editor.org/info/rfc4193>.
[RFC4389] D. Thaler, M. D., Talwar, M., and C. Patel, "Neighbor Discovery
Proxies (ND Proxy)", RFC 4389. 4389, DOI 10.17487/RFC4389, April
2006, <https://www.rfc-editor.org/info/rfc4389>.
[RFC4429] N. Moore, N., "Optimistic Duplicate Address Detection (DAD)
for IPv6", RFC 4429. 4429, DOI 10.17487/RFC4429, April 2006,
<https://www.rfc-editor.org/info/rfc4429>.
[RFC4903] D. Thaler, D., "Multi-Link Subnet Issues", RFC 4903. 4903,
DOI 10.17487/RFC4903, June 2007,
<https://www.rfc-editor.org/info/rfc4903>.
[RFC5517] S. HomChaudhuri, S. and M. Foschiano, "Cisco Systems' Private
VLANs: Scalable Security in a Multi-Client Environment",
RFC 5517. 5517, DOI 10.17487/RFC5517, February 2010,
<https://www.rfc-editor.org/info/rfc5517>.
[RFC6085] S. Gundavelli, M. S., Townsley, O. M., Troan, O., and W. Dec,
"Address Mapping of IPv6 Multicast Packets on Ethernet",
RFC 6085. 6085, DOI 10.17487/RFC6085, January 2011,
<https://www.rfc-editor.org/info/rfc6085>.
[RFC6105] E. Levy-Abegnoli, G. E., Van de Velde, C. G., Popoviciu, C., and J.
Mohacsi, "IPv6 Router Advertisement Guard", RFC 6105. 6105,
DOI 10.17487/RFC6105, February 2011,
<https://www.rfc-editor.org/info/rfc6105>.
[RFC6459] J. Korhonen, J. J., Ed., Soininen, B. J., Patil, T. B., Savolainen, G.
T., Bajko, G., and K. Iisakkila, "IPv6 in 3rd Generation
Partnership Project (3GPP) Evolved Packet System (EPS)",
RFC 6459. 6459, DOI 10.17487/RFC6459, January 2012,
<https://www.rfc-editor.org/info/rfc6459>.
[RFC6575] H. Shah, E. H., Ed., Rosen, G. E., Ed., Heron, G., Ed., and V.
Kompella, Ed., "Address Resolution Protocol (ARP)
Mediation for IP Interworking of Layer 2 VPNs", RFC 6575. 6575,
DOI 10.17487/RFC6575, June 2012,
<https://www.rfc-editor.org/info/rfc6575>.
[RFC6583] I. Gashinsky, J. I., Jaeggli, J., and W. Kumari, "Operational
Neighbor Discovery Problems", RFC 6583. 6583,
DOI 10.17487/RFC6583, March 2012,
<https://www.rfc-editor.org/info/rfc6583>.
[RFC6762] S. Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762. 6762,
DOI 10.17487/RFC6762, February 2013,
<https://www.rfc-editor.org/info/rfc6762>.
[RFC6775] Z. Shelby, S. Z., Ed., Chakrabarti, E. S., Nordmark, E., and C.
Bormann, "Neighbor Discovery Optimization for IPv6 over
Low-Power Wireless Personal Area Networks (6LoWPANs)",
RFC 6775. 6775, DOI 10.17487/RFC6775, November 2012,
<https://www.rfc-editor.org/info/rfc6775>.
[RFC6957] F. Costa, J-M. F., Combes, X. J., Ed., Pougnard, X., and H. Li,
"Duplicate Address Detection Proxy", RFC 6957 6957,
DOI 10.17487/RFC6957, June 2013,
<https://www.rfc-editor.org/info/rfc6957>.
[RFC7039] J. Wu, J. J., Bi, M. J., Bagnulo, F. M., Baker, F., and C. Vogt, Ed.,
"Source Address Validation Improvement (SAVI) Framework",
RFC
7039. 7039, DOI 10.17487/RFC7039, October 2013,
<https://www.rfc-editor.org/info/rfc7039>.
[RFC7066] J. Korhonen, J. J., Ed., Arkko, T. J., Ed., Savolainen, T., and S.
Krishnan, "IPv6 for Third Generation Partnership Project
(3GPP) Cellular Hosts", RFC 7066. 7066, DOI 10.17487/RFC7066,
November 2013, <https://www.rfc-editor.org/info/rfc7066>.
[RFC7102] JP. Vasseur, JP., "Terms Used in Routing for Low-Power and
Lossy Networks", RFC 7102. 7102, DOI 10.17487/RFC7102, January
2014, <https://www.rfc-editor.org/info/rfc7102>.
[RFC7113] F. Gont, F., "Implementation Advice for IPv6 Router
Advertisement Guard (RA-Guard)", RFC 7113. 7113,
DOI 10.17487/RFC7113, February 2014,
<https://www.rfc-editor.org/info/rfc7113>.
[RFC7278] Extending Byrne, C., Drown, D., and A. Vizdal, "Extending an IPv6
/64 Prefix from a Third Generation Partnership Project
(3GPP) Mobile Interface to a LAN Link", RFC7278. RFC 7278,
DOI 10.17487/RFC7278, June 2014,
<https://www.rfc-editor.org/info/rfc7278>.
[RFC7342] L. Dunbar, W. L., Kumari, W., and I. Gashinsky, "Practices for
Scaling ARP and Neighbor Discovery (ND) in Large Data
Centers", RFC 7342. 7342, DOI 10.17487/RFC7342, August 2014,
<https://www.rfc-editor.org/info/rfc7342>.
[RFC7527] R. Asati, H. R., Singh, W. H., Beebee, C. W., Pignataro, E. C., Dart, E.,
and W. George, "Enhanced Duplicate Address Detection",
RFC 7527. 7527, DOI 10.17487/RFC7527, April 2015,
<https://www.rfc-editor.org/info/rfc7527>.
[RFC7586] Y. Nachum, L. Y., Dunbar, I. L., Yerushalmi, I., and T. Mizrahi,
"The Scalable Address Resolution Protocol (SARP) for Large
Data Centers", RFC7586. RFC 7586, DOI 10.17487/RFC7586, June 2015,
<https://www.rfc-editor.org/info/rfc7586>.
[RFC7772] A. Yourtchenko, A. and L. Colitti, "Reducing Energy
Consumption of Router Advertisements", BCP 202, RFC 7772. 7772,
DOI 10.17487/RFC7772, February 2016,
<https://www.rfc-editor.org/info/rfc7772>.
[RFC8273] J. Brzozowski, J. and G. Van de Velde, "Unique IPv6 Prefix
per Host", RFC 8273. 8273, DOI 10.17487/RFC8273, December 2017,
<https://www.rfc-editor.org/info/rfc8273>.
[RFC8302] Y. Li, D. Y., Eastlake 3rd, L. D., Dunbar, R. L., Perlman, R., and M.
Umair, "Transparent Interconnection of Lots of Links
(TRILL): ARP and Neighbor Discovery (ND) Optimization",
RFC 8302. 8302, DOI 10.17487/RFC8302, January 2018,
<https://www.rfc-editor.org/info/rfc8302>.
[RFC8415] T. Mrugalski, M. T., Siodelski, A. M., Volz, B., Yourtchenko, M. A.,
Richardson,
S. M., Jiang, T. S., Lemon, T., and T. Winters,
"Dynamic Host Configuration Protocol for IPv6 (DHCPv6)",
RFC 8415. 8415, DOI 10.17487/RFC8415, November 2018,
<https://www.rfc-editor.org/info/rfc8415>.
[RFC8505] P. Thubert, E. P., Ed., Nordmark, S. E., Chakrabarti, S., and C.
Perkins, "Registration Extensions for IPv6 over Low-Power
Wireless Personal Area Network (6LoWPAN) Neighbor
Discovery", RFC
8505. 8505, DOI 10.17487/RFC8505, November 2018,
<https://www.rfc-editor.org/info/rfc8505>.
[RFC8928] P. Thubert, B. P., Ed., Sarikaya, M. B., Sethi, M., and R. Struik, "Address-
Protected
"Address-Protected Neighbor Discovery for Low-Power and
Lossy Networks", RFC 8928. 8928, DOI 10.17487/RFC8928, November
2020, <https://www.rfc-editor.org/info/rfc8928>.
[RFC8929] P. Thubert, C.E. P., Ed., Perkins, C.E., and E. Levy-Abegnoli,
"IPv6 Backbone Router", RFC 8929. 8929, DOI 10.17487/RFC8929,
November 2020, <https://www.rfc-editor.org/info/rfc8929>.
[RFC9099] E. Vyncke, K. É., Chittimaneni, M. K., Kaeo, M., and E. Rey,
"Operational Security Considerations for IPv6 Networks",
RFC 9099. 9099, DOI 10.17487/RFC9099, August 2021,
<https://www.rfc-editor.org/info/rfc9099>.
[RFC9119] C. Perkins, M. C., McBride, D. M., Stanley, W. D., Kumari, W., and JC. Zuniga,
Zúñiga, "Multicast Considerations over IEEE 802 Wireless
Media", RFC 9119. 9119, DOI 10.17487/RFC9119, October 2021,
<https://www.rfc-editor.org/info/rfc9119>.
[RFC9131] J. Linkova, J., "Gratuitous Neighbor Discovery: Creating
Neighbor Cache Entries on First-Hop Routers", RFC 9131. 9131,
DOI 10.17487/RFC9131, October 2021,
<https://www.rfc-editor.org/info/rfc9131>.
[RFC9161] J. Rabadan, S. J., Ed., Sathappan, K. S., Nagaraj, G. K., Hankins, G.,
and T. King, "Operational Aspects of Proxy ARP/ND in
Ethernet Virtual Private Networks", RFC 9161. 9161,
DOI 10.17487/RFC9161, January 2022,
<https://www.rfc-editor.org/info/rfc9161>.
[RFC9663] L. Colitti, J. L., Linkova, J., Ed., and X. Ma, Ed., "Using DHCP-PD
DHCPv6 Prefix Delegation (DHCPv6-PD) to Allocate Unique
IPv6 Prefix Prefixes per Client in Large Broadcast Networks",
RFC 9663. 9663, DOI 10.17487/RFC9663, October 2024,
<https://www.rfc-editor.org/info/rfc9663>.
[RFC9686] W. Kumari, S. W., Krishnan, R. S., Asati, L. R., Colitti, J. L., Linkova,
J., and S. Jiang, "Registering Self-generated Self-Generated IPv6
Addresses using Using DHCPv6", RFC 9686. 9686, DOI 10.17487/RFC9686,
December 2024, <https://www.rfc-editor.org/info/rfc9686>.
[RIPE738] IPv6 RIPE, "IPv6 Address Allocation and Assignment Policy,
https://www.ripe.net/publications/docs/ripe-738 Policy",
RIPE-738, March 2020,
<https://www.ripe.net/publications/docs/ripe-738>.
[SND] P. Thubert, P. and M. Richardson, "Architecture and Framework
for IPv6 over Non-Broadcast Access", Internet draft, June
2023. Work in Progress,
May 2025, <https://datatracker.ietf.org/doc/html/draft-
ietf-6man-ipv6-over-wireless-08>.
[TR177] S. Ooghe, B. Varga, W. Dec, D. Allan, Broadband Forum, "IPv6 in the context of TR-101", Broadband Forum, TR-177.
8. Acknowledgments TR-177,
November 2017,
<https://www.broadband-forum.org/pdfs/tr-177-1-0-1.pdf>.
Acknowledgements
The authors would like to thank Eric Vyncke, Gunter Van de Velde,
Lorenzo Colitti, Erik Kline, Warren Kumari, Mohamed Boucadair, Gorry
Fairhurst, Pascal Thubert, Jen Linkova, Brian Carpenter, Mike
Ackermann, Nalini Elkins, Ed Horley, Ole Troan, David Thaler,
Chongfeng Xie, Chris Cummings, Dale Carder, Tim Chown, Priyanka
Sinha, Aijun Wang, Ines Robles, Magnus Westerlund, Barry Leiba, Deb
Cooley
Cooley, and Paul Wouters for their reviews and comments. The authors
would also like to thank Tim Winters for being the document shepherd.
Authors' Addresses
XiPeng Xiao
Huawei Technologies Dusseldorf
Hansaallee 205, 40549 Dusseldorf, Germany
Email: xipengxiao@huawei.com
Eduard Vasilenko
Huawei Technologies
17/4 Krylatskaya st, Moscow, Russia 121614
Email: vasilenko.eduard@huawei.com
Eduard Metz
KPN N.V.
Email: eduard.metz@kpn.com
Gyan Mishra
Verizon Inc.
Email: gyan.s.mishra@verizon.com
Nick Buraglio
Energy Sciences Network
Email: buraglio@es.net