rfc9099.original   rfc9099.txt 
OPSEC E. Vyncke Internet Engineering Task Force (IETF) É. Vyncke
Internet-Draft Cisco Request for Comments: 9099 Cisco
Intended status: Informational K. Chittimaneni Category: Informational K. Chittimaneni
Expires: November 7, 2021 Square ISSN: 2070-1721
M. Kaeo M. Kaeo
Double Shot Security Double Shot Security
E. Rey E. Rey
ERNW ERNW
May 6, 2021 August 2021
Operational Security Considerations for IPv6 Networks Operational Security Considerations for IPv6 Networks
draft-ietf-opsec-v6-27
Abstract Abstract
Knowledge and experience on how to operate IPv4 networks securely is Knowledge and experience on how to operate IPv4 networks securely is
available: whether it is an Internet Service Provider or an available, whether the operator is an Internet Service Provider (ISP)
enterprise internal network. However, IPv6 presents some new or an enterprise internal network. However, IPv6 presents some new
security challenges. RFC 4942 describes security issues in the security challenges. RFC 4942 describes security issues in the
protocol, but network managers also need a more practical, protocol, but network managers also need a more practical,
operations-minded document to enumerate advantages and/or operations-minded document to enumerate advantages and/or
disadvantages of certain choices. disadvantages of certain choices.
This document analyzes the operational security issues associated This document analyzes the operational security issues associated
with several types of network and proposes technical and procedural with several types of networks and proposes technical and procedural
mitigation techniques. This document is only applicable to managed mitigation techniques. This document is only applicable to managed
networks, such as enterprise networks, service provider networks, or networks, such as enterprise networks, service provider networks, or
managed residential networks. managed residential networks.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This document is not an Internet Standards Track specification; it is
provisions of BCP 78 and BCP 79. published for informational purposes.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are candidates for any level of Internet
Standard; see Section 2 of RFC 7841.
This Internet-Draft will expire on November 7, 2021. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9099.
Copyright Notice Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction
1.1. Applicability Statement . . . . . . . . . . . . . . . . . 4 1.1. Applicability Statement
2. Generic Security Considerations . . . . . . . . . . . . . . . 4 1.2. Requirements Language
2.1. Addressing . . . . . . . . . . . . . . . . . . . . . . . 4 2. Generic Security Considerations
2.1.1. Use of ULAs . . . . . . . . . . . . . . . . . . . . . 5 2.1. Addressing
2.1.2. Point-to-Point Links . . . . . . . . . . . . . . . . 5 2.1.1. Use of ULAs
2.1.3. Loopback Addresses . . . . . . . . . . . . . . . . . 5 2.1.2. Point-to-Point Links
2.1.4. Stable Addresses . . . . . . . . . . . . . . . . . . 6 2.1.3. Loopback Addresses
2.1.5. Temporary Addresses for SLAAC . . . . . . . . . . . . 6 2.1.4. Stable Addresses
2.1.6. DHCP Considerations . . . . . . . . . . . . . . . . . 8 2.1.5. Temporary Addresses for SLAAC
2.1.7. DNS Considerations . . . . . . . . . . . . . . . . . 8 2.1.6. DHCP Considerations
2.1.8. Using a /64 per host . . . . . . . . . . . . . . . . 8 2.1.7. DNS Considerations
2.1.9. Privacy consideration of Addresses . . . . . . . . . 8 2.1.8. Using a /64 per Host
2.2. Extension Headers . . . . . . . . . . . . . . . . . . . . 9 2.1.9. Privacy Consideration of Addresses
2.2.1. Order and Repetition of Extension Headers . . . . . . 9 2.2. Extension Headers
2.2.2. Hop-by-Hop Options Header . . . . . . . . . . . . . . 10 2.2.1. Order and Repetition of Extension Headers
2.2.3. Fragment Header . . . . . . . . . . . . . . . . . . . 10 2.2.2. Hop-by-Hop Options Header
2.2.4. IP Security Extension Header . . . . . . . . . . . . 10 2.2.3. Fragment Header
2.3. Link-Layer Security . . . . . . . . . . . . . . . . . . . 11 2.2.4. IP Security Extension Header
2.3.1. Neighbor Solicitation Rate-Limiting . . . . . . . . . 11 2.3. Link-Layer Security
2.3.2. Router and Neighbor Advertisements Filtering . . . . 12 2.3.1. Neighbor Solicitation Rate-Limiting
2.3.3. Securing DHCP . . . . . . . . . . . . . . . . . . . . 13 2.3.2. Router and Neighbor Advertisements Filtering
2.3.4. 3GPP Link-Layer Security . . . . . . . . . . . . . . 14 2.3.3. Securing DHCP
2.3.5. Impact of Multicast Traffic . . . . . . . . . . . . . 15 2.3.4. 3GPP Link-Layer Security
2.3.6. SeND and CGA . . . . . . . . . . . . . . . . . . . . 15 2.3.5. Impact of Multicast Traffic
2.4. Control Plane Security . . . . . . . . . . . . . . . . . 16 2.3.6. SEND and CGA
2.4.1. Control Protocols . . . . . . . . . . . . . . . . . . 17 2.4. Control Plane Security
2.4.2. Management Protocols . . . . . . . . . . . . . . . . 18 2.4.1. Control Protocols
2.4.3. Packet Exceptions . . . . . . . . . . . . . . . . . . 18 2.4.2. Management Protocols
2.5. Routing Security . . . . . . . . . . . . . . . . . . . . 19 2.4.3. Packet Exceptions
2.5.1. BGP Security . . . . . . . . . . . . . . . . . . . . 20 2.5. Routing Security
2.5.2. Authenticating OSPFv3 Neighbors . . . . . . . . . . . 20 2.5.1. BGP Security
2.5.3. Securing Routing Updates . . . . . . . . . . . . . . 21 2.5.2. Authenticating OSPFv3 Neighbors
2.5.4. Route Filtering . . . . . . . . . . . . . . . . . . . 21 2.5.3. Securing Routing Updates
2.6. Logging/Monitoring . . . . . . . . . . . . . . . . . . . 21 2.5.4. Route Filtering
2.6.1. Data Sources . . . . . . . . . . . . . . . . . . . . 23 2.6. Logging/Monitoring
2.6.2. Use of Collected Data . . . . . . . . . . . . . . . . 26 2.6.1. Data Sources
2.6.3. Summary . . . . . . . . . . . . . . . . . . . . . . . 29 2.6.2. Use of Collected Data
2.7. Transition/Coexistence Technologies . . . . . . . . . . . 29 2.6.3. Summary
2.7.1. Dual Stack . . . . . . . . . . . . . . . . . . . . . 30 2.7. Transition/Coexistence Technologies
2.7.2. Encapsulation Mechanisms . . . . . . . . . . . . . . 31 2.7.1. Dual Stack
2.7.3. Translation Mechanisms . . . . . . . . . . . . . . . 35 2.7.2. Encapsulation Mechanisms
2.8. General Device Hardening . . . . . . . . . . . . . . . . 37 2.7.3. Translation Mechanisms
3. Enterprises Specific Security Considerations . . . . . . . . 37 2.8. General Device Hardening
3.1. External Security Considerations . . . . . . . . . . . . 38 3. Enterprises-Specific Security Considerations
3.2. Internal Security Considerations . . . . . . . . . . . . 39 3.1. External Security Considerations
4. Service Providers Security Considerations . . . . . . . . . . 40 3.2. Internal Security Considerations
4.1. BGP . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 4. Service Provider Security Considerations
4.1.1. Remote Triggered Black Hole Filtering (RTBH) . . . . 40 4.1. BGP
4.2. Transition/Coexistence Mechanism . . . . . . . . . . . . 40 4.1.1. Remote Triggered Black Hole Filtering
4.3. Lawful Intercept . . . . . . . . . . . . . . . . . . . . 40 4.2. Transition/Coexistence Mechanism
5. Residential Users Security Considerations . . . . . . . . . . 41 4.3. Lawful Intercept
6. Further Reading . . . . . . . . . . . . . . . . . . . . . . . 41 5. Residential Users Security Considerations
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 42 6. Further Reading
8. Security Considerations . . . . . . . . . . . . . . . . . . . 42 7. Security Considerations
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 42 8. IANA Considerations
9.1. Normative References . . . . . . . . . . . . . . . . . . 42 9. References
9.2. Informative References . . . . . . . . . . . . . . . . . 42 9.1. Normative References
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 57 9.2. Informative References
Acknowledgements
Authors' Addresses
1. Introduction 1. Introduction
Running an IPv6 network is new for most operators not only because Running an IPv6 network is new for most operators not only because
they are not yet used to large-scale IPv6 networks but also because they are not yet used to large-scale IPv6 networks but also because
there are subtle but critical and important differences between IPv4 there are subtle but critical and important differences between IPv4
and IPv6, especially with respect to security. For example, all and IPv6, especially with respect to security. For example, all
layer-2 interactions are now done using Neighbor Discovery Protocol Layer 2 (L2) interactions are now done using the Neighbor Discovery
[RFC4861] rather than using Address Resolution Protocol [RFC0826]. Protocol (NDP) [RFC4861] rather than the Address Resolution Protocol
Also, there is no Network Address Port Translation (NAPT) defined in [RFC0826]. Also, there is no Network Address Port Translation (NAPT)
[RFC2663] for IPv6 even if [RFC6296] specifies a Network Prefix defined in [RFC2663] for IPv6 even if [RFC6296] specifies an IPv6-to-
Translation for IPv6 (NPTv6) which is a 1-to-1 mapping of IPv6 IPv6 Network Prefix Translation (NPTv6), which is a 1-to-1 mapping of
addresses. Another important difference is that IPv6 is extensible IPv6 addresses. Another important difference is that IPv6 is
with the use of extension headers. extensible with the use of extension headers.
IPv6 networks are deployed using a variety of techniques, each of IPv6 networks are deployed using a variety of techniques, each of
which have their own specific security concerns. which have their own specific security concerns.
This document complements [RFC4942] by listing security issues when This document complements [RFC4942] by listing security issues when
operating a network (including various transition technologies). It operating a network (including various transition technologies). It
also provides more recent operational deployment experiences where also provides operational deployment experiences where warranted.
warranted.
1.1. Applicability Statement 1.1. Applicability Statement
This document is applicable to managed networks, i.e., when the This document is applicable to managed networks, i.e., when the
network is operated by the user organization itself. Indeed, many of network is operated by the user organization itself. Indeed, many of
the recommended mitigation techniques must be configured with the recommended mitigation techniques must be configured with
detailed knowledge of the network (which are the default routers, the detailed knowledge of the network (which are the default routers, the
switch trunk ports, etc.). This covers Service Provider (SP), switch trunk ports, etc.). This covers Service Providers (SPs),
enterprise networks and some knowledgeable-home-user-managed enterprise networks, and some knowledgeable home-user-managed
residential networks. This applicability statement especially residential networks. This applicability statement especially
applies to Section 2.3 and Section 2.5.4. applies to Sections 2.3 and 2.5.4.
1.2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. Generic Security Considerations 2. Generic Security Considerations
2.1. Addressing 2.1. Addressing
IPv6 address allocations and overall architecture are an important IPv6 address allocations and overall architecture are important parts
part of securing IPv6. Initial designs, even if intended to be of securing IPv6. Initial designs, even if intended to be temporary,
temporary, tend to last much longer than expected. Although tend to last much longer than expected. Although IPv6 was initially
initially IPv6 was thought to make renumbering easy, in practice it thought to make renumbering easy, in practice, it may be extremely
may be extremely difficult to renumber without a proper IP Address difficult to renumber without a proper IP Address Management (IPAM)
Management (IPAM) system. [RFC7010] introduces the mechanisms that system. [RFC7010] introduces the mechanisms that could be utilized
could be utilized for IPv6 site renumbering and tries to cover most for IPv6 site renumbering and tries to cover most of the explicit
of the explicit issues and requirements associated with IPv6 issues and requirements associated with IPv6 renumbering.
renumbering.
A key task for a successful IPv6 deployment is to prepare an A key task for a successful IPv6 deployment is to prepare an
addressing plan. Because an abundance of address space is available, addressing plan. Because an abundance of address space is available,
structuring an address plan around both services and geographic structuring an address plan around both services and geographic
locations allows address space to become a basis for more structured locations allows address space to become a basis for more structured
security policies to permit or deny services between geographic security policies to permit or deny services between geographic
regions. [RFC6177] documents some operational considerations of regions. [RFC6177] documents some operational considerations of
using different prefix sizes for address assignments at end sites. using different prefix sizes for address assignments at end sites.
A common question is whether companies should use Provider A common question is whether companies should use Provider-
Independent (PI) vs. Provider Allocated (PA) space [RFC7381], but Independent (PI) or Provider-Aggregated (PA) space [RFC7381], but,
from a security perspective there is little difference. However, one from a security perspective, there is little difference. However,
aspect to keep in mind is who has administrative ownership of the one aspect to keep in mind is who has administrative ownership of the
address space and who is technically responsible if/when there is a address space and who is technically responsible if/when there is a
need to enforce restrictions on routability of the space, e.g., due need to enforce restrictions on routability of the space, e.g., due
to malicious criminal activity originating from it. Relying on PA to malicious criminal activity originating from it. Relying on PA
address space may also increase the perceived need for address address space may also increase the perceived need for address
translation techniques such as NPTv6 and thereby augmenting the translation techniques, such as NPTv6; thereby, the complexity of the
complexity of the operations including the security operations. operations, including the security operations, is augmented.
In [RFC7934], it is recommended that IPv6 network deployments provide In [RFC7934], it is recommended that IPv6 network deployments provide
multiple IPv6 addresses from each prefix to general-purpose hosts and multiple IPv6 addresses from each prefix to general-purpose hosts,
it specifically does not recommend limiting a host to only one IPv6 and it specifically does not recommend limiting a host to only one
address per prefix. It also recommends that the network give the IPv6 address per prefix. It also recommends that the network give
host the ability to use new addresses without requiring explicit the host the ability to use new addresses without requiring explicit
requests (for example by using SLAAC). Privacy Extensions as of requests (for example, by using Stateless Address Autoconfiguration
[RFC8981] constitute one of the main scenarios where hosts are (SLAAC)). Privacy extensions, as of [RFC8981], constitute one of the
expected to generate multiple addresses from the same prefix and main scenarios where hosts are expected to generate multiple
having multiple IPv6 addresses per interface is a major change addresses from the same prefix, and having multiple IPv6 addresses
compared to the unique IPv4 address per interface for hosts per interface is a major change compared to the unique IPv4 address
(secondary IPv4 addresses are not common); especially for audits (see per interface for hosts (secondary IPv4 addresses are not common),
section Section 2.6.2.3). especially for audits (see Section 2.6.2.3).
2.1.1. Use of ULAs 2.1.1. Use of ULAs
Unique Local Addresses (ULAs) [RFC4193] are intended for scenarios Unique Local Addresses (ULAs) [RFC4193] are intended for scenarios
where interfaces are not globally reachable, despite being routed where interfaces are not globally reachable, despite being routed
within a domain. They formally have global scope, but [RFC4193] within a domain. They formally have global scope, but [RFC4193]
specifies that they must be filtered at domain boundaries. ULAs are specifies that they must be filtered at domain boundaries. ULAs are
different from [RFC1918] addresses and have different use cases. One different from the addresses described in [RFC1918] and have
use of ULA is described in [RFC4864], another one is for internal different use cases. One use of ULAs is described in [RFC4864];
communication stability in networks where external connectivity may another one is for internal communication stability in networks where
come and go (e.g., some ISPs provide ULAs in home networks connected external connectivity may come and go (e.g., some ISPs provide ULAs
via a cable modem). It should further be kept in mind that ULA /48s in home networks connected via a cable modem). It should further be
from the fd00::/8 space (L=1) MUST be generated with a pseudo-random kept in mind that ULA /48s from the fd00::/8 space (L=1) MUST be
algorithm, per [RFC4193] section 3.2.1. generated with a pseudorandom algorithm, per Section 3.2.1 of
[RFC4193].
2.1.2. Point-to-Point Links 2.1.2. Point-to-Point Links
[RFC6164] in section 5.1 specifies the rationale of using /127 for Section 5.1 of [RFC6164] specifies the rationale of using /127 for
inter-router point-to-point links to prevent the ping-pong issue inter-router, point-to-point links to prevent the ping-pong issue
between routers not correctly implementing [RFC4443] and also between routers not correctly implementing [RFC4443], and it also
prevents a DoS attack on the neighbor cache. The previous prevents a denial-of-service (DoS) attack on the Neighbor Cache. The
recommendation of [RFC3627] has been obsoleted and marked Historic by previous recommendation of [RFC3627] has been obsoleted and marked
[RFC6547]). Historic by [RFC6547].
Some environments are also using link-local addressing for point-to- Some environments are also using link-local addressing for point-to-
point links. While this practice could further reduce the attack point links. While this practice could further reduce the attack
surface of infrastructure devices, the operational disadvantages also surface of infrastructure devices, the operational disadvantages also
need to be carefully considered; see also [RFC7404]. need to be carefully considered; see [RFC7404].
2.1.3. Loopback Addresses 2.1.3. Loopback Addresses
Many operators reserve a /64 block for all loopback addresses in Many operators reserve a /64 block for all loopback addresses in
their infrastructure and allocate a /128 out of this reserved /64 their infrastructure and allocate a /128 out of this reserved /64
prefix for each loopback interface. This practice facilitates prefix for each loopback interface. This practice facilitates
configuration of Access Control List (ACL) rules to enforce a configuration of Access Control List (ACL) rules to enforce a
security policy for those loopback addresses. security policy for those loopback addresses.
2.1.4. Stable Addresses 2.1.4. Stable Addresses
When considering how to assign stable addresses for nodes (either by When considering how to assign stable addresses for nodes (either by
static configuration or by pre-provisioned DHCPv6 lease static configuration or by pre-provisioned DHCPv6 lease
Section 2.1.6), it is necessary to take into consideration the (Section 2.1.6)), it is necessary to take into consideration the
effectiveness of perimeter security in a given environment. effectiveness of perimeter security in a given environment.
There is a trade-off between ease of operation (where some portions There is a trade-off between ease of operation (where some portions
of the IPv6 address could be easily recognizable for operational of the IPv6 address could be easily recognizable for operational
debugging and troubleshooting) versus the risk of trivial scanning debugging and troubleshooting) versus the risk of trivial scanning
used for reconnaissance. [SCANNING] shows that there are used for reconnaissance. [SCANNING] shows that there are
scientifically based mechanisms that make scanning for IPv6 reachable scientifically based mechanisms that make scanning for IPv6-reachable
nodes more feasible than expected; see also [RFC7707]. nodes more feasible than expected; see [RFC7707].
Stable addresses also allow easy enforcement of a security policy at Stable addresses also allow easy enforcement of a security policy at
the perimeter based on IPv6 addresses. E.g., Manufacturer Usage the perimeter based on IPv6 addresses. For example, Manufacturer
Description (MUD) [RFC8520] is a mechanism where the perimeter Usage Description (MUD) [RFC8520] is a mechanism where the perimeter
defense can retrieve security policy template based on the type of defense can retrieve the security policy template based on the type
internal device and apply the right security policy based on the of internal device and apply the right security policy based on the
device IPv6 address. device's IPv6 address.
The use of well-known IPv6 addresses (such as ff02::1 for all link- The use of well-known IPv6 addresses (such as ff02::1 for all link-
local nodes) or the use of commonly repeated addresses could make it local nodes) or the use of commonly repeated addresses could make it
easy to figure out which devices are name servers, routers, or other easy to figure out which devices are name servers, routers, or other
critical devices; even a simple traceroute will expose most of the critical devices; even a simple traceroute will expose most of the
routers on a path. There are many scanning techniques possible and routers on a path. There are many scanning techniques possible and
operators should not rely on the 'impossible to find because my operators should not rely on the 'impossible to find because my
address is random' paradigm (a.k.a. "security by obscurity"), even if address is random' paradigm (a.k.a. "security by obscurity") even if
it is common practice to have the stable addresses randomly it is common practice to have the stable addresses randomly
distributed across /64 subnets and to always use DNS (as IPv6 distributed across /64 subnets and to always use DNS (as IPv6
addresses are hard for human brains to remember). addresses are hard for human brains to remember).
While in some environments obfuscating addresses could be considered While, in some environments, obfuscating addresses could be
an added benefit, it should not preclude enforcement of perimeter considered an added benefit, it should not preclude enforcement of
rules. Stable addresses following some logical allocation scheme may perimeter rules. Stable addresses following some logical allocation
ease the operation (as simplicity always helps security). scheme may ease the operation (as simplicity always helps security).
Typical deployments will have a mix of stable and non-stable Typical deployments will have a mix of stable and non-stable
addresses; the stable addresses being either predictable (e.g., ::25 addresses; the stable addresses being either predictable (e.g., ::25
for a mail server) or obfuscated (i.e., appearing as a random 64-bit for a mail server) or obfuscated (i.e., appearing as a random 64-bit
number). number).
2.1.5. Temporary Addresses for SLAAC 2.1.5. Temporary Addresses for SLAAC
Historically, stateless address autoconfiguration (SLAAC) makes up Historically, Stateless Address Autoconfiguration (SLAAC) makes up
the globally unique IPv6 address based on an automatically generated the globally unique IPv6 address based on an automatically generated
64-bit interface identifier (IID) based on the EUI-64 MAC address 64-bit interface identifier (IID) based on the 64-bit Extended Unique
combined with the /64 prefix (received in the Prefix Information Identifier (EUI-64) Media Access Control (MAC) address combined with
Option (PIO) of the Router Advertisement (RA)). The EUI-64 address the /64 prefix (received in the Prefix Information Option (PIO) of
is generated from the stable 48-bit MAC address and does not change the Router Advertisement (RA)). The EUI-64 address is generated from
even if the host moves to another network; this is of course bad for the stable 48-bit MAC address and does not change even if the host
privacy as a host can be traced from network (home) to network moves to another network; this is of course bad for privacy, as a
(office or Wi-Fi in hotels). [RFC8064] recommends against the use of host can be traced from network (home) to network (office or Wi-Fi in
EUI-64 addresses; and it must be noted that most host operating hotels). [RFC8064] recommends against the use of EUI-64 addresses,
systems do not use EUI-64 addresses anymore and rely on either and it must be noted that most host operating systems do not use
[RFC8981] or [RFC8064]. EUI-64 addresses anymore and rely on either [RFC8981] or [RFC8064].
Randomly generating an interface ID, as described in [RFC8981], is Randomly generating an interface ID, as described in [RFC8981], is
part of SLAAC with so-called privacy extension addresses and is used part of SLAAC with so-called privacy extension addresses and is used
to address some privacy concerns. Privacy extension addresses, to address some privacy concerns. Privacy extension addresses,
a.k.a., temporary addresses may help to mitigate the correlation of a.k.a. temporary addresses, may help to mitigate the correlation of
activities of a node within the same network and may also reduce the activities of a node within the same network and may also reduce the
attack exposure window. But using [RFC8981] privacy extension attack exposure window. But using privacy extension addresses as
addresses might prevent the operator from building host specific described in [RFC8981] might prevent the operator from building host-
access control lists (ACLs). The [RFC8981] privacy extension specific access control lists (ACLs). These privacy extension
addresses could also be used to obfuscate some malevolent activities addresses could also be used to obfuscate some malevolent activities,
and specific user attribution/accountability procedures should be put and specific user attribution/accountability procedures should be put
in place as described in Section 2.6. in place, as described in Section 2.6.
[RFC8064] combined with the address generation mechanism of [RFC7217] [RFC8064] combined with the address generation mechanism of [RFC7217]
specifies another way to generate an address while still keeping the specifies another way to generate an address while still keeping the
same IID for each network prefix; this allows SLAAC nodes to always same IID for each network prefix; this allows SLAAC nodes to always
have the same stable IPv6 address on a specific network while having have the same stable IPv6 address on a specific network while having
different IPv6 addresses on different networks. different IPv6 addresses on different networks.
In some specific use cases where user accountability is more In some specific use cases where user accountability is more
important than user privacy, network operators may consider disabling important than user privacy, network operators may consider disabling
SLAAC and relying only on DHCPv6; but not all operating systems SLAAC and relying only on DHCPv6; however, not all operating systems
support DHCPv6 so some hosts will not get any IPv6 connectivity. support DHCPv6, so some hosts will not get any IPv6 connectivity.
Disabling SLAAC and privacy extension addresses can be done for most Disabling SLAAC and privacy extension addresses can be done for most
operating systems by sending RA messages with a hint to get addresses operating systems by sending RA messages with a hint to get addresses
via DHCPv6 by setting the M-bit and disabling SLAAC by resetting all via DHCPv6 by setting the M-bit and disabling SLAAC by resetting all
A-bits in all prefix information options. However, attackers could A-bits in all PIOs. However, attackers could still find ways to
still find ways to bypass this mechanism if not enforced at the bypass this mechanism if it is not enforced at the switch/router
switch/router level. level.
However, in scenarios where anonymity is a strong desire (protecting However, in scenarios where anonymity is a strong desire (protecting
user privacy is more important than user attribution), privacy user privacy is more important than user attribution), privacy
extension addresses should be used. When mechanisms recommended by extension addresses should be used. When mechanisms recommended by
[RFC8064] are available, the stable privacy address is probably a [RFC8064] are available, the stable privacy address is probably a
good balance between privacy (among different networks) and security/ good balance between privacy (among different networks) and security/
user attribution (within a network). user attribution (within a network).
2.1.6. DHCP Considerations 2.1.6. DHCP Considerations
Some environments use DHCPv6 to provision addresses and other Some environments use DHCPv6 to provision addresses and other
parameters in order to ensure auditability and traceability (see parameters in order to ensure auditability and traceability (see
Section 2.6.1.5 for the limitations of DHCPv6 for auditability). Section 2.6.1.5 for the limitations of DHCPv6 for auditability).
A main security concern is the ability to detect and counteract rogue A main security concern is the ability to detect and counteract rogue
DHCP servers (Section 2.3.3). It must be noted that as opposed to DHCP servers (Section 2.3.3). It must be noted that, as opposed to
DHCPv4, DHCPv6 can lease several IPv6 addresses per client. For DHCPv4, DHCPv6 can lease several IPv6 addresses per client. For
DHCPv4, the lease is bound to the 'client identifier', which may DHCPv4, the lease is bound to the 'client identifier', which may
contain a hardware address, or it may contain another type of contain a hardware address or another type of identifier, such as a
identifier, such as a DNS name. For DHCPv6, the lease is bound to DNS name. For DHCPv6, the lease is bound to the client DHCP Unique
the client DHCP Unique ID (DUID), which may, or may not, be bound to Identifier (DUID), which may or may not be bound to the client L2
the client link-layer address. [RFC7824] describes the privacy address. [RFC7824] describes the privacy issues associated with the
issues associated with the use of DHCPv6 by Internet users. The use of DHCPv6 by Internet users. The anonymity profiles [RFC7844]
anonymity profiles [RFC7844] are designed for clients that wish to are designed for clients that wish to remain anonymous to the visited
remain anonymous to the visited network. [RFC7707] recommends that network. [RFC7707] recommends that DHCPv6 servers issue addresses
DHCPv6 servers issue addresses randomly from a large pool. randomly from a large pool.
2.1.7. DNS Considerations 2.1.7. DNS Considerations
While the security concerns of DNS are not fundamentally different While the security concerns of DNS are not fundamentally different
between IPv4 and IPv6, there are specific considerations in DNS64 between IPv4 and IPv6, there are specific considerations in DNS64
[RFC6147] environments that need to be understood. Specifically, the [RFC6147] environments that need to be understood. Specifically, the
interactions and the potential of interference with DNSSEC interactions and the potential of interference with DNSSEC [RFC4033]
([RFC4033]) implementation need to be understood - these are pointed implementation need to be understood -- these are pointed out in more
out in more detail in Section 2.7.3.2. detail in Section 2.7.3.2.
2.1.8. Using a /64 per host 2.1.8. Using a /64 per Host
An interesting approach is using a /64 per host as proposed in An interesting approach is using a /64 per host, as proposed in
[RFC8273] especially in a shared environment. This allows for easier [RFC8273], especially in a shared environment. This allows for
user attribution (typically based on the host MAC address) as its /64 easier user attribution (typically based on the host MAC address), as
prefix is stable even if applications within the host can change its /64 prefix is stable, even if applications within the host can
their IPv6 address within this /64 prefix. change their IPv6 address within this /64 prefix.
This can also be useful for the generation of ACLs once individual This can also be useful for the generation of ACLs once individual
systems (e.g. admin workstations) have their own prefixes. systems (e.g., admin workstations) have their own prefixes.
2.1.9. Privacy consideration of Addresses 2.1.9. Privacy Consideration of Addresses
Beside the security aspects of IPv6 addresses, there are also privacy In addition to the security aspects of IPv6 addresses, there are also
considerations: mainly because they are of global scope and visible privacy considerations: mainly because they are of global scope and
globally. [RFC7721] goes into more detail on the privacy visible globally. [RFC7721] goes into more detail on the privacy
considerations for IPv6 addresses by comparing the manually considerations for IPv6 addresses by comparing the manually
configured IPv6 address, DHCPv6, and SLAAC. configured IPv6 address, DHCPv6, and SLAAC.
2.2. Extension Headers 2.2. Extension Headers
Extension headers are an important difference between IPv4 and IPv6. Extension headers are an important difference between IPv4 and IPv6.
In IPv4-based packets, it's trivial to find the upper-layer protocol In IPv4-based packets, it's trivial to find the upper-layer protocol
type and protocol header, while in IPv6 it is more complex since the type and protocol header, while, in IPv6, it is more complex since
extension header chain must be parsed completely (even if not the extension header chain must be parsed completely (even if not
processed) in order to find the upper-layer protocol header. IANA processed) in order to find the upper-layer protocol header. IANA
has closed the existing empty "Next Header Types" registry to new has closed the existing empty "Next Header Types" registry to new
entries and is redirecting its users to a new "IPv6 Extension Header entries and is redirecting its users to the "IPv6 Extension Header
Types" registry per [RFC7045]. Types" registry, per [RFC7045].
Extension headers have also become a very controversial topic since Extension headers have also become a very controversial topic since
forwarding nodes that discard packets containing extension headers forwarding nodes that discard packets containing extension headers
are known to cause connectivity failures and deployment problems are known to cause connectivity failures and deployment problems
[RFC7872]. Understanding the role of various extension headers is [RFC7872]. Understanding the role of various extension headers is
important and this section enumerates the ones that need careful important, and this section enumerates the ones that need careful
consideration. consideration.
A clarification on how intermediate nodes should handle packets with A clarification on how intermediate nodes should handle packets with
existing or future extension headers is found in [RFC7045]. The existing or future extension headers is found in [RFC7045]. The
uniform TLV format to be used for defining future extension headers uniform TLV format to be used for defining future extension headers
is described in [RFC6564]. Sections 5.2 and 5.3 of [RFC8504] provide is described in [RFC6564]. Sections 5.2 and 5.3 of [RFC8504] provide
more information on the processing of extension headers by IPv6 more information on the processing of extension headers by IPv6
nodes. nodes.
Vendors of filtering solutions and operations personnel responsible Vendors of filtering solutions and operations personnel responsible
for implementing packet filtering rules should be aware that the for implementing packet filtering rules should be aware that the
'Next Header' field in an IPv6 header can both point to an IPv6 'Next Header' field in an IPv6 header can both point to an IPv6
extension header or to an upper layer protocol header. This has to extension header or to an upper-layer protocol header. This has to
be considered when designing the user interface of filtering be considered when designing the user interface of filtering
solutions or during the creation of filtering rule sets. solutions or during the creation of filtering rule sets.
There is IETF work in progress regarding filtering rules for those [IPV6-EH-FILTERING] discusses filtering rules for those extension
extension headers: [I-D.ietf-opsec-ipv6-eh-filtering] for transit headers at transit routers.
routers.
2.2.1. Order and Repetition of Extension Headers 2.2.1. Order and Repetition of Extension Headers
While [RFC8200] recommends the order and the maximum repetition of While [RFC8200] recommends the order and the maximum repetition of
extension headers, there are still IPv6 implementations, at the time extension headers, at the time of writing, there are still IPv6
of writing, which support a non-recommended order of headers (such as implementations that support an order of headers that is not
ESP before routing) or an illegal repetition of headers (such as recommended (such as Encapsulating Security Payload (ESP) before
multiple routing headers). The same applies for options contained in routing) or an illegal repetition of headers (such as multiple
the extension headers (see [I-D.kampanakis-6man-ipv6-eh-parsing]). routing headers). The same applies for options contained in the
In some cases, it has led to nodes crashing when receiving or extension headers (see [IPV6-EH-PARSING]). In some cases, it has led
forwarding wrongly formatted packets. to nodes crashing when receiving or forwarding wrongly formatted
packets.
A firewall or edge device should be used to enforce the recommended A firewall or edge device should be used to enforce the recommended
order and the maximum occurrences of extension headers by dropping order and the maximum occurrences of extension headers by dropping
non-conforming packets. nonconforming packets.
2.2.2. Hop-by-Hop Options Header 2.2.2. Hop-by-Hop Options Header
In the previous IPv6 specification [RFC2460], the hop-by-hop options In the previous IPv6 specification [RFC2460], the hop-by-hop options
header, when present in an IPv6 packet, forced all nodes to inspect header, when present in an IPv6 packet, forced all nodes to inspect
and possibly process this header. This enabled denial-of-service and possibly process this header. This enabled denial-of-service
attacks as most, if not all, routers cannot process this type of attacks as most, if not all, routers cannot process this type of
packet in hardware but have to process these packets in software and packet in hardware; they have to process these packets in software
hence compete with other software tasks, such as handling the control and, hence, this task competes with other software tasks, such as
and management plane processing. handling the control and management plane processing.
Section 4.3 of the current Internet Standard for IPv6, [RFC8200], has Section 4.3 of [RFC8200], the current Internet Standard for IPv6, has
taken this attack vector into account and made the processing of hop- taken this attack vector into account and made the processing of hop-
by-hop options headers by intermediate routers explicitly by-hop options headers by intermediate routers explicitly
configurable. configurable.
2.2.3. Fragment Header 2.2.3. Fragment Header
The fragment header is used by the source (and only the source) when The fragment header is used by the source (and only the source) when
it has to fragment packets. [RFC7112] and section 4.5 of [RFC8200] it has to fragment packets. [RFC7112] and Section 4.5 of [RFC8200]
explain why it is important that: explain why it is important that:
Firewall and security devices should drop first fragments that do * Firewall and security devices should drop first fragments that do
not contain the entire IPv6 header chain (including the transport- not contain the entire IPv6 header chain (including the transport-
layer header). layer header).
Destination nodes should discard first fragments that do not * Destination nodes should discard first fragments that do not
contain the entire IPv6 header chain (including the transport- contain the entire IPv6 header chain (including the transport-
layer header). layer header).
If those requirements are not met, stateless filtering could be If those requirements are not met, stateless filtering could be
bypassed by a hostile party. [RFC6980] applies a stricter rule to bypassed by a hostile party. [RFC6980] applies a stricter rule to
Neighbor Discovery Protocol (NDP) by enforcing the drop of fragmented NDP by enforcing the drop of fragmented NDP packets (except for
NDP packets (except for "Certification Path Advertisement" messages "Certification Path Advertisement" messages, as noted in section
as noted in section Section 2.3.2.1). [RFC7113] describes how the Section 2.3.2.1). [RFC7113] describes how the RA-Guard function
RA-guard function described in [RFC6105] should behave in the described in [RFC6105] should behave in the presence of fragmented RA
presence of fragmented RA packets. packets.
2.2.4. IP Security Extension Header 2.2.4. IP Security Extension Header
The IPsec [RFC4301] extension headers (AH [RFC4302] and ESP The IPsec [RFC4301] extension headers (Authentication Header (AH)
[RFC4303]) are required if IPsec is to be utilized for network level [RFC4302] and ESP [RFC4303]) are required if IPsec is to be utilized
security. Previously, IPv6 mandated implementation of IPsec but for network-level security. Previously, IPv6 mandated implementation
[RFC6434] updated that recommendation by making support of the IPsec of IPsec, but [RFC6434] updated that recommendation by making support
architecture [RFC4301] a SHOULD for all IPv6 nodes which is also of the IPsec architecture [RFC4301] a 'SHOULD' for all IPv6 nodes
retained in the latest IPv6 Nodes Requirement standard [RFC8504]. that are also retained in the latest IPv6 Nodes Requirement standard
[RFC8504].
2.3. Link-Layer Security 2.3. Link-Layer Security
IPv6 relies heavily on NDP [RFC4861] to perform a variety of link IPv6 relies heavily on NDP [RFC4861] to perform a variety of link
operations such as discovering other nodes on the link, resolving operations, such as discovering other nodes on the link, resolving
their link-layer addresses, and finding routers on the link. If not their link-layer addresses, and finding routers on the link. If not
secured, NDP is vulnerable to various attacks, such as router/ secured, NDP is vulnerable to various attacks, such as router/
neighbor message spoofing, redirect attacks, Duplicate Address neighbor message spoofing, redirect attacks, Duplicate Address
Detection (DAD) DoS attacks, etc. Many of these security threats to Detection (DAD) DoS attacks, etc. Many of these security threats to
NDP have been documented in IPv6 ND Trust Models and Threats NDP have been documented in "IPv6 Neighbor Discovery (ND) Trust
[RFC3756] and in [RFC6583]. Models and Threats" [RFC3756] and in "Operational Neighbor Discovery
Problems" [RFC6583].
Most of the issues are only applicable when the attacker is on the Most of the issues are only applicable when the attacker is on the
same link but NDP also has security issues when the attacker is off- same link, but NDP also has security issues when the attacker is off
link, see the section below Section 2.3.1. link; see Section 2.3.1 below.
2.3.1. Neighbor Solicitation Rate-Limiting 2.3.1. Neighbor Solicitation Rate-Limiting
NDP can be vulnerable to remote denial of service (DoS) attacks; for NDP can be vulnerable to remote DoS attacks, for example, when a
example, when a router is forced to perform address resolution for a router is forced to perform address resolution for a large number of
large number of unassigned addresses, i.e., when a prefix is scanned unassigned addresses, i.e., when a prefix is scanned by an attacker
by an attacker in a fast manner. This can keep new devices from in a fast manner. This can keep new devices from joining the network
joining the network or render the last-hop router ineffective due to or render the last-hop router ineffective due to high CPU usage.
high CPU usage. Easy mitigative steps include rate-limiting Neighbor Easy mitigative steps include rate limiting Neighbor Solicitations,
Solicitations, restricting the amount of state reserved for restricting the amount of state reserved for unresolved
unresolved solicitations, and clever cache/timer management. solicitations, and cleverly managing the cache/timer.
[RFC6583] discusses the potential for off-link DoS in detail and [RFC6583] discusses the potential for off-link DoS in detail and
suggests implementation improvements and operational mitigation suggests implementation improvements and operational mitigation
techniques that may be used to mitigate or alleviate the impact of techniques that may be used to mitigate or alleviate the impact of
such attacks. Here are some feasible mitigation options that can be such attacks. Here are some feasible mitigation options that can be
employed by network operators today: employed by network operators today:
o Ingress filtering of unused addresses by ACL. These require * Ingress filtering of unused addresses by ACL. These require
stable configuration of the addresses; for example, allocating the stable configuration of the addresses, e.g., allocating the
addresses out of a /120 and using a specific ACL to only allow addresses out of a /120 and using a specific ACL to only allow
traffic to this /120 (of course, the actual hosts are configured traffic to this /120 (of course, the actual hosts are configured
with a /64 prefix for the link). with a /64 prefix for the link).
o Tuning of NDP process (where supported), e.g., enforcing limits on * Tuning of NDP process (where supported), e.g., enforcing limits on
data structures such as the number of neighbor cache entries in data structures, such as the number of Neighbor Cache entries in
'incomplete' state (e.g., 256 incomplete entries per interface) or 'incomplete' state (e.g., 256 incomplete entries per interface) or
the rate of NA per interface (e.g., 100 NA per second). the rate of NA per interface (e.g., 100 NA per second).
o Using a /127 on a point-to-point link, per [RFC6164]. * Using a /127 on a point-to-point link, per [RFC6164].
o Using only link-local addresses on links where there are only * Using only link-local addresses on links where there are only
routers, see [RFC7404] routers; see [RFC7404].
2.3.2. Router and Neighbor Advertisements Filtering 2.3.2. Router and Neighbor Advertisements Filtering
2.3.2.1. Router Advertisement Filtering 2.3.2.1. Router Advertisement Filtering
Router Advertisement spoofing is a well-known on-link attack vector Router Advertisement spoofing is a well-known, on-link attack vector
and has been extensively documented. The presence of rogue RAs, and has been extensively documented. The presence of rogue RAs,
either unintentional or malicious, can cause partial or complete either unintentional or malicious, can cause partial or complete
failure of operation of hosts on an IPv6 link. For example, a node failure of operation of hosts on an IPv6 link. For example, a node
can select an incorrect router address which can then be used for an can select an incorrect router address, which can then be used for an
on-path attack or the node can assume wrong prefixes to be used for on-path attack, or the node can assume wrong prefixes to be used for
SLAAC. [RFC6104] summarizes the scenarios in which rogue RAs may be SLAAC. [RFC6104] summarizes the scenarios in which rogue RAs may be
observed and presents a list of possible solutions to the problem. observed and presents a list of possible solutions to the problem.
[RFC6105] (RA-Guard) describes a solution framework for the rogue RA [RFC6105] (RA-Guard) describes a solution framework for the rogue RA
problem where network segments are designed around switching devices problem where network segments are designed around switching devices
that are capable of identifying invalid RAs and blocking them before that are capable of identifying invalid RAs and blocking them before
the attack packets actually reach the target nodes. the attack packets actually reach the target nodes.
However, several evasion techniques that circumvent the protection However, several evasion techniques that circumvent the protection
provided by RA-Guard have surfaced. A key challenge to this provided by RA-Guard have surfaced. A key challenge to this
mitigation technique is introduced by IPv6 fragmentation. Attackers mitigation technique is introduced by IPv6 fragmentation. Attackers
can conceal their attack by fragmenting their packets into multiple can conceal their attack by fragmenting their packets into multiple
fragments such that the switching device that is responsible for fragments such that the switching device that is responsible for
blocking invalid RAs cannot find all the necessary information to blocking invalid RAs cannot find all the necessary information to
perform packet filtering of the same packet. [RFC7113] describes perform packet filtering of the same packet. [RFC7113] describes
such evasion techniques and provides advice to RA-Guard implementers such evasion techniques and provides advice to RA-Guard implementers
such that the aforementioned evasion vectors can be eliminated. such that the aforementioned evasion vectors can be eliminated.
Given that the IPv6 Fragmentation Header can be leveraged to Given that the IPv6 Fragmentation Header can be leveraged to
circumvent some implementations of RA-Guard, [RFC6980] updates circumvent some implementations of RA-Guard, [RFC6980] updates
[RFC4861] such that use of the IPv6 Fragmentation Header is forbidden [RFC4861] such that use of the IPv6 Fragmentation Header is forbidden
in all Neighbor Discovery messages except "Certification Path in all Neighbor Discovery messages, except "Certification Path
Advertisement", thus allowing for simple and effective measures to Advertisement", thus allowing for simple and effective measures to
counter fragmented NDP attacks. counter fragmented NDP attacks.
2.3.2.2. Neighbor Advertisement Filtering 2.3.2.2. Neighbor Advertisement Filtering
The Source Address Validation Improvements (SAVI) working group has The Source Address Validation Improvements (savi) Working Group has
worked on other ways to mitigate the effects of such attacks. worked on other ways to mitigate the effects of such attacks.
[RFC7513] helps in creating bindings between a DHCPv4 [RFC2131] [RFC7513] helps in creating bindings between a source IP address
/DHCPv6 [RFC8415] assigned source IP address and a binding anchor assigned to DHCPv4 [RFC2131] or DHCPv6 [RFC8415] and a binding anchor
[RFC7039] on a SAVI device. Also, [RFC6620] describes how to glean [RFC7039] on a SAVI device. Also, [RFC6620] describes how to glean
similar bindings when DHCP is not used. The bindings can be used to similar bindings when DHCP is not used. The bindings can be used to
filter packets generated on the local link with forged source IP filter packets generated on the local link with forged source IP
addresses. addresses.
2.3.2.3. Host Isolation 2.3.2.3. Host Isolation
Isolating hosts for the NDP traffic can be done by using a /64 per Isolating hosts for the NDP traffic can be done by using a /64 per
host, refer to Section 2.1.8, as NDP is only relevant within a /64 host, refer to Section 2.1.8, as NDP is only relevant within a /64
on-link prefix; 3GPP Section 2.3.4 uses a similar mechanism. on-link prefix; 3GPP (Section 2.3.4) uses a similar mechanism.
A more drastic technique to prevent all NDP attacks is based on A more drastic technique to prevent all NDP attacks is based on
isolation of all hosts with specific configurations. In such a isolation of all hosts with specific configurations. In such a
scenario, hosts (i.e., all nodes that are not routers) are unable to scenario, hosts (i.e., all nodes that are not routers) are unable to
send data-link layer frames to other hosts, therefore, no host-to- send data-link layer frames to other hosts; therefore, no host-to-
host attacks can happen. This specific setup can be established on host attacks can happen. This specific setup can be established on
some switches or Wi-Fi access points. This is not always feasible some switches or Wi-Fi access points. This is not always feasible
when hosts need to communicate with other hosts in the same subnet, when hosts need to communicate with other hosts in the same subnet,
e.g., for access to file shares. e.g., for access to file shares.
2.3.2.4. NDP Recommendations 2.3.2.4. NDP Recommendations
It is still recommended that RA-Guard and SAVI be employed as a first It is still recommended that RA-Guard and SAVI be employed as a first
line of defense against common attack vectors including misconfigured line of defense against common attack vectors, including
hosts. This recommendation also applies when DHCPv6 is used, as RA misconfigured hosts. This recommendation also applies when DHCPv6 is
messages are used to discover the default router(s) and for on-link used, as RA messages are used to discover the default router(s) and
prefix determination. This line of defense is most effective when for on-link prefix determination. This line of defense is most
incomplete fragments are dropped by routers and switches as described effective when incomplete fragments are dropped by routers and L2
in Section 2.2.3. The generated log should also be analyzed to switches, as described in Section 2.2.3. The generated log should
identify and act on violations. also be analyzed to identify and act on violations.
Network operators should be aware that RA-Guard and SAVI do not work Network operators should be aware that RA-Guard and SAVI do not work
as expected or could even be harmful in specific network as expected or could even be harmful in specific network
configurations (notably when there could be multiple routers). configurations (notably when there could be multiple routers).
Enabling RA-Guard by default in managed networks (e.g., Wi-Fi Enabling RA-Guard by default in managed networks (e.g., Wi-Fi
networks, enterprise campus networks, etc.) should be strongly networks, enterprise campus networks, etc.) should be strongly
considered except for specific use cases such as the presence of considered except for specific use cases, such as in the presence of
homenet devices emitting router advertisements. homenet devices emitting router advertisements.
2.3.3. Securing DHCP 2.3.3. Securing DHCP
The Dynamic Host Configuration Protocol for IPv6 (DHCPv6), as The Dynamic Host Configuration Protocol for IPv6 (DHCPv6), as
described in [RFC8415], enables DHCP servers to pass configuration described in [RFC8415], enables DHCP servers to pass configuration
parameters, such as IPv6 network addresses and other configuration parameters, such as IPv6 network addresses and other configuration
information, to IPv6 nodes. DHCP plays an important role in most information, to IPv6 nodes. DHCP plays an important role in most
large networks by providing robust stateful configuration in the large networks by providing robust stateful configuration in the
context of automated system provisioning. context of automated system provisioning.
The two most common threats to DHCP clients come from malicious The two most common threats to DHCP clients come from malicious
(a.k.a., rogue) or unintentionally misconfigured DHCP servers. in (a.k.a. rogue) or unintentionally misconfigured DHCP servers. In
these scenarios, a malicious DHCP server is established with the these scenarios, a malicious DHCP server is established with the
intent of providing incorrect configuration information to the intent of providing incorrect configuration information to the
clients to cause a denial-of-service attack or to mount on-path clients to cause a denial-of-service attack or to mount an on-path
attack. While unintentional, a misconfigured DHCP server can have attack. While unintentional, a misconfigured DHCP server can have
the same impact. Additional threats against DHCP are discussed in the same impact. Additional threats against DHCP are discussed in
the security considerations section of [RFC8415]. the security considerations section of [RFC8415].
DHCPv6-Shield, [RFC7610], specifies a mechanism for protecting DHCPv6-Shield [RFC7610] specifies a mechanism for protecting
connected DHCPv6 clients against rogue DHCPv6 servers. This connected DHCPv6 clients against rogue DHCPv6 servers. This
mechanism is based on DHCPv6 packet-filtering at the layer-2 device, mechanism is based on DHCPv6 packet filtering at the L2 device, i.e.,
i.e., the administrator specifies the interfaces connected to DHCPv6 the administrator specifies the interfaces connected to DHCPv6
servers. However, extension headers could be leveraged to bypass servers. However, extension headers could be leveraged to bypass
DHCPv6-Shield unless [RFC7112] is enforced. DHCPv6-Shield unless [RFC7112] is enforced.
It is recommended to use DHCPv6-Shield and to analyze the It is recommended to use DHCPv6-Shield and to analyze the
corresponding log messages. corresponding log messages.
2.3.4. 3GPP Link-Layer Security 2.3.4. 3GPP Link-Layer Security
The 3GPP link is a point-to-point like link that has no link-layer The 3GPP link is a point-to-point-like link that has no link-layer
address. This implies there can only be one end host (the mobile address. This implies there can only be one end host (the mobile
hand-set) and the first-hop router (i.e., a GPRS Gateway Support Node handset) and the first-hop router (i.e., a Gateway GPRS Support Node
(GGSN) or a Packet Gateway (PGW)) on that link. The GGSN/PGW never (GGSN) or a Packet Data Network Gateway (PGW)) on that link. The
configures a non link-local address on the link using the advertised GGSN/PGW never configures a non-link-local address on the link using
/64 prefix on it; see Section 2.1.8. The advertised prefix must not the advertised /64 prefix on it; see Section 2.1.8. The advertised
be used for on-link determination. There is no need for address prefix must not be used for on-link determination. There is no need
resolution on the 3GPP link, since there are no link-layer addresses. for address resolution on the 3GPP link, since there are no link-
Furthermore, the GGSN/PGW assigns a prefix that is unique within each layer addresses. Furthermore, the GGSN/PGW assigns a prefix that is
3GPP link that uses IPv6 stateless address autoconfiguration. This unique within each 3GPP link that uses IPv6 Stateless Address
avoids the necessity to perform DAD at the network level for every Autoconfiguration. This avoids the necessity to perform DAD at the
address generated by the mobile host. The GGSN/PGW always provides network level for every address generated by the mobile host. The
an IID to the cellular host for the purpose of configuring the link- GGSN/PGW always provides an IID to the cellular host for the purpose
local address and ensures the uniqueness of the IID on the link of configuring the link-local address and ensures the uniqueness of
(i.e., no collisions between its own link-local address and the the IID on the link (i.e., no collisions between its own link-local
mobile host's address). address and the mobile host's address).
The 3GPP link model itself mitigates most of the known NDP-related The 3GPP link model itself mitigates most of the known NDP-related
Denial-of-Service attacks. In practice, the GGSN/PGW only needs to DoS attacks. In practice, the GGSN/PGW only needs to route all
route all traffic to the mobile host that falls under the prefix traffic to the mobile host that falls under the prefix assigned to
assigned to it. As there is also a single host on the 3GPP link, it. As there is also a single host on the 3GPP link, there is no
there is no need to defend that IPv6 address. need to defend that IPv6 address.
See Section 5 of [RFC6459] for a more detailed discussion on the 3GPP See Section 5 of [RFC6459] for a more detailed discussion on the 3GPP
link model, NDP, and the address configuration details. In some link model, NDP, and the address configuration details. In some
mobile networks, DHCPv6 and DHCP-PD are also used. mobile networks, DHCPv6 and DHCP Prefix Delegation (DHCP-PD) are also
used.
2.3.5. Impact of Multicast Traffic 2.3.5. Impact of Multicast Traffic
IPv6 uses multicast extensively for signaling messages on the local IPv6 uses multicast extensively for signaling messages on the local
link to avoid broadcast messages for on-the-wire efficiency. link to avoid broadcast messages for on-the-wire efficiency.
The use of multicast has some side effects on wireless networks, such The use of multicast has some side effects on wireless networks, such
as a negative impact on battery life of smartphones and other as a negative impact on battery life of smartphones and other
battery-operated devices that are connected to such networks. battery-operated devices that are connected to such networks.
[RFC7772] and [RFC6775] (for specific wireless networks) discuss [RFC7772] and [RFC6775] (for specific wireless networks) discuss
methods to rate-limit RAs and other ND messages on wireless networks methods to rate-limit RAs and other ND messages on wireless networks
in order to address this issue. in order to address this issue.
The use of link-layer multicast addresses (e.g., ff02::1 for the all The use of link-layer multicast addresses (e.g., ff02::1 for the all
nodes link-local multicast address) could also be misused for an nodes link-local multicast address) could also be misused for an
amplification attack. Imagine, a hostile node sending an ICMPv6 amplification attack. Imagine a hostile node sending an ICMPv6
ECHO_REQUEST to ff02::1 with a spoofed source address, then, all ECHO_REQUEST to ff02::1 with a spoofed source address, then all link-
link-local nodes will reply with ICMPv6 ECHO_REPLY packets to the local nodes will reply with ICMPv6 ECHO_REPLY packets to the source
source address. This could be a DoS attack for the address owner. address. This could be a DoS attack for the address owner. This
This attack is purely local to the layer-2 network as packets with a attack is purely local to the L2 network, as packets with a link-
link-local destination are never forwarded by an IPv6 router. local destination are never forwarded by an IPv6 router.
This is the reason why large Wi-Fi network deployments often limit This is the reason why large Wi-Fi network deployments often limit
the use of link-layer multicast either from or to the uplink of the the use of link-layer multicast, either from or to the uplink of the
Wi-Fi access point, i.e., Wi-Fi stations are prevented to send link- Wi-Fi access point, i.e., Wi-Fi stations are prevented to send link-
local multicast to their direct neighboring Wi-Fi stations; this local multicast to their direct neighboring Wi-Fi stations; this
policy also blocks service discovery via mDNS ([RFC6762]) and LLMNR policy also blocks service discovery via Multicast DNS (mDNS)
([RFC4795]). [RFC6762] and Link-Local Multicast Name Resolution (LLMNR) [RFC4795].
2.3.6. SeND and CGA 2.3.6. SEND and CGA
SEcure Neighbor Discovery (SeND), as described in [RFC3971], is a SEcure Neighbor Discovery (SEND), as described in [RFC3971], is a
mechanism that was designed to secure ND messages. This approach mechanism that was designed to secure ND messages. This approach
involves the use of new NDP options to carry public key-based involves the use of new NDP options to carry public-key-based
signatures. Cryptographically Generated Addresses (CGA), as signatures. Cryptographically Generated Addresses (CGA), as
described in [RFC3972], are used to ensure that the sender of a described in [RFC3972], are used to ensure that the sender of a
Neighbor Discovery message is the actual "owner" of the claimed IPv6 Neighbor Discovery message is the actual "owner" of the claimed IPv6
address. A new NDP option, the CGA option, was introduced and is address. A new NDP option, the CGA option, was introduced and is
used to carry the public key and associated parameters. Another NDP used to carry the public key and associated parameters. Another NDP
option, the RSA Signature option, is used to protect all messages option, the RSA Signature option, is used to protect all messages
relating to neighbor and Router discovery. relating to neighbor and router discovery.
SeND protects against: SEND protects against:
o Neighbor Solicitation/Advertisement Spoofing * Neighbor Solicitation/Advertisement Spoofing
o Neighbor Unreachability Detection Failure * Neighbor Unreachability Detection Failure
o Duplicate Address Detection DoS Attack * Duplicate Address Detection DoS Attack
o Router Solicitation and Advertisement Attacks
o Replay Attacks * Router Solicitation and Advertisement Attacks
o Neighbor Discovery DoS Attacks * Replay Attacks
SeND does NOT: * Neighbor Discovery DoS Attacks
o Protect statically configured addresses SEND does NOT:
o Protect addresses configured using fixed identifiers (i.e., EUI- * protect statically configured addresses
* protect addresses configured using fixed identifiers (i.e., EUI-
64) 64)
o Provide confidentiality for NDP communications * provide confidentiality for NDP communications
o Compensate for an unsecured link - SeND does not require that the * compensate for an unsecured link -- SEND does not require that the
addresses on the link and Neighbor Advertisements correspond. addresses on the link and Neighbor Advertisements correspond
However, at this time and over a decade since their original However, at this time and over a decade since their original
specifications, CGA and SeND do not have support from widely deployed specifications, CGA and SEND do not have support from widely deployed
IPv6 devices; hence, their usefulness is limited and should not be IPv6 devices; hence, their usefulness is limited and should not be
relied upon. relied upon.
2.4. Control Plane Security 2.4. Control Plane Security
[RFC6192] defines the router control plane and provides detailed [RFC6192] defines the router control plane and provides detailed
guidance to secure it for IPv4 and IPv6 networks. This definition is guidance to secure it for IPv4 and IPv6 networks. This definition is
repeated here for the reader's convenience. Please note that the repeated here for the reader's convenience. Please note that the
definition is completely protocol-version agnostic (most of this definition is completely protocol-version agnostic (most of this
section applies to IPv6 in the same way as to IPv4). section applies to IPv6 in the same way as to IPv4).
Preamble: IPv6 control plane security is vastly congruent with its | Preamble: IPv6 control plane security is vastly congruent with
IPv4 equivalent with the exception of OSPFv3 authentication | its IPv4 equivalent, with the exception of OSPFv3
(Section 2.4.1) and some packet exceptions (see Section 2.4.3) that | authentication (Section 2.4.1) and some packet exceptions (see
are specific to IPv6. | Section 2.4.3) that are specific to IPv6.
Modern router architecture design maintains a strict separation of Modern router architecture design maintains a strict separation of
forwarding and router control plane hardware and software. The forwarding and router control plane hardware and software. The
router control plane supports routing and management functions. It router control plane supports routing and management functions. It
is generally described as the router architecture hardware and is generally described as the router architecture hardware and
software components for handling packets destined to the device software components for handling packets destined to the device
itself, as well as, building and sending packets originated locally itself as well as building and sending packets originated locally on
on the device. The forwarding plane is typically described as the the device. The forwarding plane is typically described as the
router architecture hardware and software components responsible for router architecture hardware and software components responsible for
receiving a packet on an incoming interface, performing a lookup to receiving a packet on an incoming interface, performing a lookup to
identify the packet's IP next hop and best outgoing interface towards identify the packet's IP next hop and best outgoing interface towards
the destination, and forwarding the packet through the appropriate the destination, and forwarding the packet through the appropriate
outgoing interface. outgoing interface.
While the forwarding plane is usually implemented in high-speed While the forwarding plane is usually implemented in high-speed
hardware, the control plane is implemented by a generic processor hardware, the control plane is implemented by a generic processor
(referred to as the route processor (RP)) and cannot process packets (referred to as the routing processor (RP)) and cannot process
at a high rate. Hence, this processor can be attacked by flooding packets at a high rate. Hence, this processor can be attacked by
its input queue with more packets than it can process. The control flooding its input queue with more packets than it can process. The
plane processor is then unable to process valid control packets and control plane processor is then unable to process valid control
the router can lose IGP or BGP adjacencies which can cause a severe packets and the router can lose IGP or BGP adjacencies, which can
network disruption. cause a severe network disruption.
[RFC6192] provides detailed guidance to protect the router control [RFC6192] provides detailed guidance to protect the router control
plane in IPv6 networks. The rest of this section contains simplified plane in IPv6 networks. The rest of this section contains simplified
guidance. guidance.
The mitigation techniques are: The mitigation techniques are:
o To drop non-legit or potentially harmful control packets before * to drop illegitimate or potentially harmful control packets before
they are queued to the RP (this can be done by a forwarding plane they are queued to the RP (this can be done by a forwarding plane
ACL) and ACL) and
o To rate-limit the remaining packets to a rate that the RP can * to rate-limit the remaining packets to a rate that the RP can
sustain. Protocol-specific protection should also be done (for sustain. Protocol-specific protection should also be done (for
example, a spoofed OSPFv3 packet could trigger the execution of example, a spoofed OSPFv3 packet could trigger the execution of
the Dijkstra algorithm, therefore, the frequency of Dijsktra the Dijkstra algorithm; therefore, the frequency of Dijkstra
calculations should be also rate-limited). calculations should also be rate limited).
This section will consider several classes of control packets: This section will consider several classes of control packets:
o Control protocols: routing protocols: such as OSPFv3, BGP, RIPng, Control protocols:
and by extension NDP and ICMP routing protocols, such as OSPFv3, BGP, Routing Information
Protocol Next Generation (RIPng), and, by extension, NDP and ICMP
o Management protocols: SSH, SNMP, NETCONF, RESTCONF, IPFIX, etc. Management protocols:
Secure Shell (SSH), SNMP, Network Configuration Protocol
(NETCONF), RESTCONF, IP Flow Information Export (IPFIX), etc.
o Packet exceptions: normal data packets that require a specific Packet exceptions:
processing such as generating a packet-too-big ICMP message or normal data packets that require a specific processing, such as
processing the hop-by-hop options header. generating a packet-too-big ICMP message or processing the hop-by-
hop options header
2.4.1. Control Protocols 2.4.1. Control Protocols
This class includes OSPFv3, BGP, NDP, ICMP. This class includes OSPFv3, BGP, NDP, and ICMP.
An ingress ACL to be applied on all the router interfaces for packets An ingress ACL to be applied on all the router interfaces for packets
to be processed by the RP should be configured to: to be processed by the RP should be configured to:
o drop OSPFv3 (identified by Next-Header being 89) and RIPng * drop OSPFv3 (identified by Next-Header being 89) and RIPng
(identified by UDP port 521) packets from a non link-local address (identified by UDP port 521) packets from a non-link-local address
(except for OSPFv3 virtual links) (except for OSPFv3 virtual links)
o allow BGP (identified by TCP port 179) packets from all BGP * allow BGP (identified by TCP port 179) packets from all BGP
neighbors and drop the others neighbors and drop the others
o allow all ICMP packets (transit and to the router interfaces) * allow all ICMP packets (transit and to the router interfaces)
Note: dropping OSPFv3 packets which are authenticated by IPsec could | Note: Dropping OSPFv3 packets that are authenticated by IPsec
be impossible on some routers that are unable to parse the IPsec ESP | could be impossible on some routers that are unable to parse
or AH extension headers during ACL classification. | the IPsec ESP or AH extension headers during ACL
| classification.
Rate-limiting of the valid packets should be done, see also [RFC8541] Rate-limiting of the valid packets should be done; see [RFC8541] for
for a side benefit for OSPv3. The exact configuration will depend on a side benefit for OSPv3. The exact configuration will depend on the
the available resources of the router (CPU, TCAM, ...). available resources of the router (CPU, Ternary Content-Addressable
Memory (TCAM), etc.).
2.4.2. Management Protocols 2.4.2. Management Protocols
This class includes: SSH, SNMP, RESTCONF, NETCONF, gRPC, syslog, NTP, This class includes SSH, SNMP, RESTCONF, NETCONF, gRPC Remote
etc. Procedure Calls (gRPC), syslog, NTP, etc.
An ingress ACL to be applied on all the router interfaces (or at An ingress ACL to be applied on all the router interfaces (or at
ingress interfaces of the security perimeter or by using specific ingress interfaces of the security perimeter or by using specific
features of the platform) should be configured for packets destined features of the platform) should be configured for packets destined
to the RP such as: to the RP, such as:
o Drop packets destined to the routers except those belonging to * drop packets destined to the routers, except those belonging to
protocols which are used (for example, permit TCP 22 and drop all protocols that are used (for example, permit TCP 22 and drop all
others when only SSH is used); others when only SSH is used) and
o Drop packets where the source does not match the security policy, * drop packets where the source does not match the security policy
for example, if SSH connections should only be originated from the (for example, if SSH connections should only be originated from
Network Operation Center (NOC), then the ACL should permit TCP the Network Operation Center (NOC), then the ACL should permit TCP
port 22 packets only from the NOC prefix. port 22 packets only from the NOC prefix).
Rate-limiting of valid packets should be done. The exact Rate-limiting of valid packets should be done. The exact
configuration will depend on the available router resources. configuration will depend on the available router resources.
2.4.3. Packet Exceptions 2.4.3. Packet Exceptions
This class covers multiple cases where a data plane packet is punted This class covers multiple cases where a data plane packet is punted
to the route processor because it requires specific processing: to the route processor because it requires specific processing:
o generation of an ICMP packet-too-big message when a data plane * generation of an ICMP packet-too-big message when a data plane
packet cannot be forwarded because it is too large (required to packet cannot be forwarded because it is too large (required to
discover the Path MTU); discover the Path MTU);
o generation of an ICMP hop-limit-expired message when a data plane * generation of an ICMP hop-limit-expired message when a data plane
packet cannot be forwarded because its hop-limit field has reached packet cannot be forwarded because its hop-limit field has reached
0 (also used by the traceroute utility); 0 (also used by the traceroute utility);
o generation of an ICMP destination-unreachable message when a data * generation of an ICMP destination-unreachable message when a data
plane packet cannot be forwarded for any reason; plane packet cannot be forwarded for any reason;
o processing of the hop-by-hop options header, new implementations * processing of the hop-by-hop options header; new implementations
follow section 4.3 of [RFC8200] where this processing is optional; follow Section 4.3 of [RFC8200] where this processing is optional;
or
o or more specific to some router implementation: an oversized * more specific to some router implementations, an oversized
extension header chain which cannot be processed by the hardware extension header chain that cannot be processed by the hardware
and force the packet to be punted to the RP. and cannot force the packet to be punted to the RP.
On some routers, not everything can be done by the specialized data On some routers, not everything can be done by the specialized data
plane hardware which requires some packets to be 'punted' to the plane hardware that requires some packets to be 'punted' to the
generic RP. This could include for example the processing of a long generic RP. This could include, for example, the processing of a
extension header chain in order to apply an ACL based on layer-4 long extension header chain in order to apply an ACL based on Layer 4
information. [RFC6980] and more generally [RFC7112] highlight the information. [RFC6980] and more generally [RFC7112] highlight the
security implications of oversized extension header chains on routers security implications of oversized extension header chains on routers
and updates the original IPv6 specifications, [RFC2460], such that and update the original IPv6 specifications [RFC2460] such that the
the first fragment of a packet is required to contain the entire IPv6 first fragment of a packet is required to contain the entire IPv6
header chain. Those changes are incorporated in the IPv6 standard header chain. Those changes are incorporated in the IPv6 standard
[RFC8200] [RFC8200].
An ingress ACL cannot mitigate a control plane attack using these An ingress ACL cannot mitigate a control plane attack using these
packet exceptions. The only protection for the RP is to rate-limit packet exceptions. The only protection for the RP is to rate-limit
those packet exceptions that are forwarded to the RP, this means that those packet exceptions that are forwarded to the RP. This means
some data plane packets will be dropped without an ICMP message sent that some data plane packets will be dropped without an ICMP message
to the source which may delay Path MTU discovery and cause drops. sent to the source, which may delay Path MTU Discovery and cause
drops.
In addition to limiting the rate of data plane packets queued to the In addition to limiting the rate of data plane packets queued to the
RP, it is also important to rate-limit the generation of ICMP RP, it is also important to rate-limit the generation of ICMP
messages. This is important both to preserve RP resources and also messages. This is important both to preserve RP resources and also
to prevent an amplification attack using the router as a reflector. to prevent an amplification attack using the router as a reflector.
It is worth noting that some platforms implement this rate-limiting It is worth noting that some platforms implement this rate-limiting
in hardware. Of course, a consequence of not generating an ICMP in hardware. Of course, a consequence of not generating an ICMP
message will break some IPv6 mechanisms such as Path MTU discovery or message will break some IPv6 mechanisms, such as Path MTU Discovery
a simple traceroute. or a simple traceroute.
2.5. Routing Security 2.5. Routing Security
Preamble: IPv6 routing security is congruent with IPv4 routing | Preamble: IPv6 routing security is congruent with IPv4 routing
security with the exception of OSPv3 neighbor authentication (see | security, with the exception of OSPv3 neighbor authentication
Section 2.5.2). | (see Section 2.5.2).
Routing security in general can be broadly divided into three Routing security in general can be broadly divided into three
sections: sections:
1. Authenticating neighbors/peers 1. authenticating neighbors/peers
2. Securing routing updates between peers 2. securing routing updates between peers
3. Route filtering
3. route filtering
[RFC5082] is also applicable to IPv6 and can ensure that routing [RFC5082] is also applicable to IPv6 and can ensure that routing
protocol packets are coming from the local network; it must also be protocol packets are coming from the local network; it must also be
noted that in IPv6 all interior gateway protocols use link-local noted that in IPv6 all interior gateway protocols use link-local
addresses. addresses.
As for IPv4, it is recommended to enable a routing protocol only on As for IPv4, it is recommended to enable a routing protocol only on
interfaces where it is required. interfaces where it is required.
2.5.1. BGP Security 2.5.1. BGP Security
As BGP is identical for IPv4 and IPv6 and as [RFC7454] covers all the As BGP is identical for IPv4 and IPv6 and as [RFC7454] covers all the
security aspects for BGP in detail, [RFC7454] is also applicable to security aspects for BGP in detail, [RFC7454] is also applicable to
IPv6. IPv6.
2.5.2. Authenticating OSPFv3 Neighbors 2.5.2. Authenticating OSPFv3 Neighbors
OSPFv3 can rely on IPsec to fulfill the authentication function. OSPFv3 can rely on IPsec to fulfill the authentication function.
Operators should note that IPsec support is not standard on all Operators should note that IPsec support is not standard on all
routing platforms. In some cases, this requires specialized hardware routing platforms. In some cases, this requires specialized hardware
that offloads crypto over to dedicated ASICs or enhanced software that offloads crypto over to dedicated Application-Specific
images (both of which often come with added financial cost) to Integrated Circuits (ASICs) or enhanced software images (both of
provide such functionality. An added detail is to determine whether which often come with added financial cost) to provide such
OSPFv3 IPsec implementations use AH or ESP-Null for integrity functionality. An added detail is to determine whether OSPFv3 IPsec
protection. In early implementations, all OSPFv3 IPsec implementations use AH or ESP-NULL for integrity protection. In
configurations relied on AH since the details weren't specified in early implementations, all OSPFv3 IPsec configurations relied on AH
[RFC5340]. However, the document which specifically describes how since the details weren't specified in [RFC5340]. However, the
IPsec should be implemented for OSPFv3 [RFC4552] specifically states document that specifically describes how IPsec should be implemented
that "ESP-Null MUST and AH MAY be implemented" since it follows the for OSPFv3 [RFC4552] states that "implementations MUST support ESP[-
overall IPsec standards wording. OSPFv3 can also use normal ESP to NULL] and MAY support AH" since it follows the overall IPsec
encrypt the OSPFv3 payload to provide confidentiality for the routing standards wording. OSPFv3 can also use normal ESP to encrypt the
OSPFv3 payload to provide confidentiality for the routing
information. information.
[RFC7166] changes OSPFv3 reliance on IPsec by appending an [RFC7166] changes OSPFv3 reliance on IPsec by appending an
authentication trailer to the end of the OSPFv3 packets; it does not authentication trailer to the end of the OSPFv3 packets. It does not
specifically authenticate the specific originator of an OSPFv3 authenticate the specific originator of an OSPFv3 packet; rather, it
packet; rather, it allows a router to confirm that the packet has allows a router to confirm that the packet has been issued by a
been issued by a router that had access to the shared authentication router that had access to the shared authentication key.
key.
With all authentication mechanisms, operators should confirm that With all authentication mechanisms, operators should confirm that
implementations can support re-keying mechanisms that do not cause implementations can support rekeying mechanisms that do not cause
outages. There have been instances where any re-keying causes outages. There have been instances where any rekeying causes
outages and therefore, the tradeoff between utilizing this outages; therefore, the trade-off between utilizing this
functionality needs to be weighed against the protection it provides. functionality needs to be weighed against the protection it provides.
[RFC4107] documents some guidelines for crypto keys management. [RFC4107] documents some guidelines for crypto keys management.
2.5.3. Securing Routing Updates 2.5.3. Securing Routing Updates
IPv6 initially mandated the provisioning of IPsec capability in all IPv6 initially mandated the provisioning of IPsec capability in all
nodes. However, in the updated IPv6 Nodes Requirement standard nodes. However, in the updated IPv6 Nodes Requirement standard
[RFC8504], IPsec is a 'SHOULD' and not a 'MUST' implement. [RFC8504], IPsec is a 'SHOULD' and not a 'MUST' implementation.
Theoretically, it is possible that all communication between two IPv6 Theoretically, it is possible that all communication between two IPv6
nodes, especially routers exchanging routing information, is nodes, especially routers exchanging routing information, is
encrypted using IPsec. In practice however, deploying IPsec is not encrypted using IPsec. However, in practice, deploying IPsec is not
always feasible given hardware and software limitations of the always feasible given hardware and software limitations of the
various platforms deployed. various platforms deployed.
Many routing protocols support the use of cryptography to protect the Many routing protocols support the use of cryptography to protect the
routing updates, the use of this protection is recommended; [RFC8177] routing updates; the use of this protection is recommended.
is a YANG data model for key chains that includes re-keying [RFC8177] is a YANG data model for key chains that includes rekeying
functionality. functionality.
2.5.4. Route Filtering 2.5.4. Route Filtering
Route filtering policies will be different depending on whether they Route filtering policies will be different depending on whether they
pertain to edge route filtering vs. internal route filtering. At a pertain to edge route filtering or internal route filtering. At a
minimum, IPv6 routing policy as it pertains to routing between minimum, the IPv6 routing policy, as it pertains to routing between
different administrative domains should aim to maintain parity with different administrative domains, should aim to maintain parity with
IPv4 from a policy perspective, e.g., IPv4 from a policy perspective, for example:
o Filter internal-use, non-globally routable IPv6 addresses at the * filter internal-use IPv6 addresses that are not globally routable
perimeter; at the perimeter;
o Discard routes for bogon [CYMRU] and reserved space (see * discard routes for bogon [CYMRU] and reserved space (see
[RFC8190]); [RFC8190]); and
o Configure ingress route filters that validate route origin, prefix * configure ingress route filters that validate route origin, prefix
ownership, etc. through the use of various routing databases, ownership, etc., through the use of various routing databases,
e.g., [RADB]. [RFC8210] formally validates the origin ASs of BGP e.g., [RADB]. [RFC8210] formally validates the origin Autonomous
announcements. Systems (ASes) of BGP announcements.
Some good guidance can be found at [RFC7454]. Some good guidance can be found at [RFC7454].
A valid routing table can also be used to apply network ingress A valid routing table can also be used to apply network ingress
filtering (see [RFC2827]). filtering (see [RFC2827]).
2.6. Logging/Monitoring 2.6. Logging/Monitoring
In order to perform forensic research in the cases of a security In order to perform forensic research in the cases of a security
incident or detecting abnormal behavior, network operators should log incident or detecting abnormal behavior, network operators should log
multiple pieces of information. In some cases, this requires a multiple pieces of information. In some cases, this requires a
frequent poll of devices via a Network Management Station. frequent poll of devices via a Network Management Station.
This logging should include, but not limited to: This logging should include but is not limited to:
o logs of all applications using the network (including user space * logs of all applications using the network (including user space
and kernel space) when available (for example web servers that the and kernel space) when available (for example, web servers that
network operator manages); the network operator manages);
o data from IP Flow Information Export [RFC7011] also known as * data from IP Flow Information Export [RFC7011], also known as
IPFIX; IPFIX;
o data from various SNMP MIBs [RFC4293] or YANG data via RESTCONF * data from various SNMP MIBs [RFC4293] or YANG data via RESTCONF
[RFC8040] or NETCONF [RFC6241]; [RFC8040] or NETCONF [RFC6241];
o historical data of Neighbor Cache entries; * historical data of Neighbor Cache entries;
o stateful DHCPv6 [RFC8415] lease cache, especially when a relay * stateful DHCPv6 [RFC8415] lease cache, especially when a relay
agent [RFC6221] is used; agent [RFC6221] is used;
o Source Address Validation Improvement (SAVI) [RFC7039] events, * Source Address Validation Improvement (SAVI) [RFC7039] events,
especially the binding of an IPv6 address to a MAC address and a especially the binding of an IPv6 address to a MAC address and a
specific switch or router interface; specific switch or router interface;
o firewall ACL log; * firewall ACL logs;
o authentication server log; * authentication server logs; and
o RADIUS [RFC2866] accounting records. * RADIUS [RFC2866] accounting records.
Please note that there are privacy issues or regulations related to Please note that there are privacy issues or regulations related to
how these logs are collected, stored, used, and safely discarded. how these logs are collected, stored, used, and safely discarded.
Operators are urged to check their country legislation (e.g., General Operators are urged to check their country legislation (e.g., General
Data Protection Regulation GDPR [GDPR] in the European Union). Data Protection Regulation [GDPR] in the European Union).
All those pieces of information can be used for: All those pieces of information can be used for:
o forensic (Section 2.6.2.1) investigations such as who did what and * forensic (Section 2.6.2.1) investigations: who did what and when?
when?
o correlation (Section 2.6.2.3): which IP addresses were used by a * correlation (Section 2.6.2.3): which IP addresses were used by a
specific node (assuming the use of privacy extensions addresses specific node (assuming the use of privacy extensions addresses
[RFC8981]) [RFC8981])?
o inventory (Section 2.6.2.2): which IPv6 nodes are on my network? * inventory (Section 2.6.2.2): which IPv6 nodes are on my network?
o abnormal behavior detection (Section 2.6.2.4): unusual traffic * abnormal behavior detection (Section 2.6.2.4): unusual traffic
patterns are often the symptoms of an abnormal behavior which is patterns are often the symptoms of an abnormal behavior, which is
in turn a potential attack (denial-of-service, network scan, a in turn a potential attack (denial of service, network scan, a
node being part of a botnet, etc.) node being part of a botnet, etc.).
2.6.1. Data Sources 2.6.1. Data Sources
This section lists the most important sources of data that are useful This section lists the most important sources of data that are useful
for operational security. for operational security.
2.6.1.1. Application Logs 2.6.1.1. Application Logs
Those logs are usually text files where the remote IPv6 address is Those logs are usually text files where the remote IPv6 address is
stored in clear text (not binary). This can complicate the stored in cleartext (not binary). This can complicate the processing
processing since one IPv6 address, for example 2001:db8::1 can be since one IPv6 address, for example, 2001:db8::1, can be written in
written in multiple ways, such as: multiple ways, such as:
o 2001:DB8::1 (in uppercase) * 2001:DB8::1 (in uppercase),
o 2001:0db8::0001 (with leading 0) * 2001:0db8::0001 (with leading 0), and
o and many other ways including the reverse DNS mapping into a FQDN * many other ways, including the reverse DNS mapping into a Fully
(which should not be trusted). Qualified Domain Name (FQDN) (which should not be trusted).
[RFC5952] explains this problem in detail and recommends the use of a [RFC5952] explains this problem in detail and recommends the use of a
single canonical format. This document recommends the use of single canonical format. This document recommends the use of
canonical format [RFC5952] for IPv6 addresses in all possible cases. canonical format [RFC5952] for IPv6 addresses in all possible cases.
If the existing application cannot log using the canonical format, If the existing application cannot log using the canonical format,
then it is recommended to use an external post-processing program in then it is recommended to use an external post-processing program in
order to canonicalize all IPv6 addresses. order to canonicalize all IPv6 addresses.
2.6.1.2. IP Flow Information Export by IPv6 Routers 2.6.1.2. IP Flow Information Export by IPv6 Routers
IPFIX [RFC7012] defines some data elements that are useful for IPFIX [RFC7012] defines some data elements that are useful for
security: security:
o nextHeaderIPv6, sourceIPv6Address, and destinationIPv6Address; * nextHeaderIPv6, sourceIPv6Address, and destinationIPv6Address
o sourceMacAddress and destinationMacAddress. * sourceMacAddress and destinationMacAddress
The IP version is the ipVersion element defined in [IANA-IPFIX]. The IP version is the ipVersion element defined in [IANA-IPFIX].
Moreover, IPFIX is very efficient in terms of data handling and Moreover, IPFIX is very efficient in terms of data handling and
transport. It can also aggregate flows by a key such as transport. It can also aggregate flows by a key, such as
sourceMacAddress in order to have aggregated data associated with a sourceMacAddress, in order to have aggregated data associated with a
specific sourceMacAddress. This memo recommends the use of IPFIX and specific sourceMacAddress. This memo recommends the use of IPFIX and
aggregation on nextHeaderIPv6, sourceIPv6Address, and aggregation on nextHeaderIPv6, sourceIPv6Address, and
sourceMacAddress. sourceMacAddress.
2.6.1.3. SNMP MIB and NETCONF/RESTCONF YANG Modules data by IPv6 2.6.1.3. SNMP MIB and NETCONF/RESTCONF YANG Modules Data by IPv6
Routers Routers
RFC 4293 [RFC4293] defines a Management Information Base (MIB) for [RFC4293] defines a Management Information Base (MIB) for the two
the two address families of IP. This memo recommends the use of: address families of IP. This memo recommends the use of:
o ipIfStatsTable table which collects traffic counters per * ipIfStatsTable table, which collects traffic counters per
interface; interface, and
o ipNetToPhysicalTable table which is the content of the Neighbor * ipNetToPhysicalTable table, which is the content of the Neighbor
cache, i.e., the mapping between IPv6 and data-link layer Cache, i.e., the mapping between IPv6 and data-link layer
addresses. addresses.
There are also YANG modules relating to the two IP addresses families There are also YANG modules relating to the two IP address families
and can be used with [RFC6241] and [RFC8040]. This memo recommends and that can be used with [RFC6241] and [RFC8040]. This memo
the use of: recommends the use of:
o interfaces-state/interface/statistics from ietf- * interfaces-state/interface/statistics from
interfaces@2018-02-20.yang [RFC8343] which contains counters for ietf-interfaces@2018-02-20.yang [RFC8343], which contains counters
interfaces. for interfaces, and
o ipv6/neighbor from ietf-ip@2018-02-22.yang [RFC8344] which is the * ipv6/neighbor from ietf-ip@2018-02-22.yang [RFC8344], which is the
content of the Neighbor cache, i.e., the mapping between IPv6 and content of the Neighbor Cache, i.e., the mapping between IPv6 and
data-link layer addresses. data-link layer addresses.
2.6.1.4. Neighbor Cache of IPv6 Routers 2.6.1.4. Neighbor Cache of IPv6 Routers
The neighbor cache of routers contains all mappings between IPv6 The Neighbor Cache of routers contains all mappings between IPv6
addresses and data-link layer addresses. There are multiple ways to addresses and data-link layer addresses. There are multiple ways to
collect the current entries in the Neighbor Cache, notably but not collect the current entries in the Neighbor Cache, notably, but not
limited to: limited to:
o the SNMP MIB (Section 2.6.1.3) as explained above; * using the SNMP MIB (Section 2.6.1.3), as explained above;
o using streaming telemetry or NETCONF [RFC6241] and RESTCONF * using streaming telemetry or NETCONF [RFC6241] and RESTCONF
[RFC8040] to collect the operational state of the neighbor cache; [RFC8040] to collect the operational state of the Neighbor Cache;
and
o also, by connecting over a secure management channel (such as SSH) * connecting over a secure management channel (such as SSH) and
and explicitly requesting a neighbor cache dump via the Command explicitly requesting a Neighbor Cache dump via the Command-Line
Line Interface (CLI) or another monitoring mechanism. Interface (CLI) or another monitoring mechanism.
The neighbor cache is highly dynamic as mappings are added when a new The Neighbor Cache is highly dynamic, as mappings are added when a
IPv6 address appears on the network. This could be quite frequently new IPv6 address appears on the network. This could be quite
with privacy extension addresses [RFC8981] or when they are removed frequently with privacy extension addresses [RFC8981] or when they
when the state goes from UNREACH to removed (the default time for a are removed when the state goes from UNREACH to removed (the default
removal per Neighbor Unreachability Detection [RFC4861] algorithm is time for a removal per Neighbor Unreachability Detection [RFC4861]
38 seconds for a host using Windows 7). This means that the content algorithm is 38 seconds for a host using Windows 7). This means that
of the neighbor cache must periodically be fetched at an interval the content of the Neighbor Cache must be fetched periodically at an
which does not exhaust the router resources and still provides interval that does not exhaust the router resources and still
valuable information (suggested value is 30 seconds but this should provides valuable information (the suggested value is 30 seconds, but
be verified in the actual deployment) and stored for later use. this should be verified in the actual deployment) and stored for
later use.
This is an important source of information because it is trivial (on This is an important source of information because it is trivial (on
a switch not using the SAVI [RFC7039] algorithm) to defeat the a switch not using the SAVI [RFC7039] algorithm) to defeat the
mapping between data-link layer address and IPv6 address. Let us mapping between data-link layer address and an IPv6 address. Put
rephrase the previous statement: having access to the current and another way, having access to the current and past content of the
past content of the neighbor cache has a paramount value for the Neighbor Cache has a paramount value for the forensic and audit
forensic and audit trail. It should also be noted that in certain trails. It should also be noted that, in certain threat models, this
threat models this information is also deemed valuable and could information is also deemed valuable and could itself be a target.
itself be a target.
When using one /64 per host (Section 2.1.8) or DHCP-PD, it is When using one /64 per host (Section 2.1.8) or DHCP-PD, it is
sufficient to keep the history of the allocated prefixes when sufficient to keep the history of the allocated prefixes when
combined with strict source address prefix enforcement on the routers combined with strict source address prefix enforcement on the routers
and layer-2 switches to prevent IPv6 spoofing. and L2 switches to prevent IPv6 spoofing.
2.6.1.5. Stateful DHCPv6 Lease 2.6.1.5. Stateful DHCPv6 Lease
In some networks, IPv6 addresses/prefixes are managed by a stateful In some networks, IPv6 addresses/prefixes are managed by a stateful
DHCPv6 server [RFC8415] that leases IPv6 addresses/prefixes to DHCPv6 server [RFC8415] that leases IPv6 addresses/prefixes to
clients. It is indeed quite similar to DHCP for IPv4, so it can be clients. It is indeed quite similar to DHCP for IPv4, so it can be
tempting to use this DHCP lease file to discover the mapping between tempting to use this DHCP lease file to discover the mapping between
IPv6 addresses/prefixes and data-link layer addresses as is commonly IPv6 addresses/prefixes and data-link layer addresses, as is commonly
used in IPv4 networking. used in IPv4 networking.
It is not so easy in the IPv6 networks, because not all nodes will It is not so easy in the IPv6 networks, because not all nodes will
use DHCPv6 (there are nodes which can only do stateless use DHCPv6 (there are nodes that can only do stateless
autoconfiguration) but also because DHCPv6 clients are identified not autoconfiguration) and also because DHCPv6 clients are identified not
by their hardware-client address as in IPv4 but by a DHCP Unique ID by their hardware-client address, as in IPv4, but by a DHCP Unique
(DUID), which can have several formats: some being the data-link Identifier (DUID). The DUID can have several formats: the data-link
layer address, some being data-link layer address prepended with time layer address, the data-link layer address prepended with time
information, or even an opaque number that requires correlation with information, or even an opaque number that requires correlation with
another data source to be usable for operational security. Moreover, another data source to be usable for operational security. Moreover,
when the DUID is based on the data-link address, this address can be when the DUID is based on the data-link address, this address can be
of any client interface (such as the wireless interface while the of any client interface (such as the wireless interface, while the
client actually uses its wired interface to connect to the network). client actually uses its wired interface to connect to the network).
If a lightweight DHCP relay agent [RFC6221] is used in a layer-2 If a lightweight DHCP relay agent [RFC6221] is used in a L2 switch,
switch, then the DHCP servers also receive the Interface-ID then the DHCP servers also receive the interface ID information,
information which could be saved in order to identify the interface which could be saved in order to identify the interface on which the
on which the switch received a specific leased IPv6 address. Also, switch received a specific leased IPv6 address. Also, if a 'normal'
if a 'normal' (not lightweight) relay agent adds the data-link layer (not lightweight) relay agent adds the data-link layer address in the
address in the option for Relay Agent Remote-ID [RFC4649] or option for Relay Agent Remote-ID [RFC4649] [RFC6939], then the DHCPv6
[RFC6939], then the DHCPv6 server can keep track of the data-link and server can keep track of the data-link and leased IPv6 addresses.
leased IPv6 addresses.
In short, the DHCPv6 lease file is less interesting than for IPv4 In short, the DHCPv6 lease file is less interesting than lease files
networks. If possible, it is recommended to use DHCPv6 servers that for IPv4 networks. If possible, it is recommended to use DHCPv6
keep the relayed data-link layer address in addition to the DUID in servers that keep the relayed data-link layer address in addition to
the lease file as those servers have the equivalent information to the DUID in the lease file, as those servers have the equivalent
IPv4 DHCP servers. information to IPv4 DHCP servers.
The mapping between data-link layer address and the IPv6 address can The mapping between the data-link layer address and the IPv6 address
be secured by deploying switches implementing the SAVI [RFC7513] can be secured by deploying switches implementing the SAVI [RFC7513]
mechanisms. Of course, this also requires that the data-link layer mechanisms. Of course, this also requires that the data-link layer
address is protected by using a layer-2 mechanism such as address be protected by using a L2 mechanism, such as [IEEE-802.1X].
[IEEE-802.1X].
2.6.1.6. RADIUS Accounting Log 2.6.1.6. RADIUS Accounting Log
For interfaces where the user is authenticated via a RADIUS [RFC2866] For interfaces where the user is authenticated via a RADIUS [RFC2866]
server, and if RADIUS accounting is enabled, then the RADIUS server server, and if RADIUS accounting is enabled, then the RADIUS server
receives accounting Acct-Status-Type records at the start and at the receives accounting Acct-Status-Type records at the start and at the
end of the connection which include all IPv6 (and IPv4) addresses end of the connection, which include all IPv6 (and IPv4) addresses
used by the user. This technique can be used notably for Wi-Fi used by the user. This technique can be used notably for Wi-Fi
networks with Wi-Fi Protected Address (WPA) or other IEEE 802.1X networks with Wi-Fi Protected Access (WPA) or other IEEE 802.1X
[IEEE-802.1X] wired interface on an Ethernet switch. [IEEE-802.1X] wired interfaces on an Ethernet switch.
2.6.1.7. Other Data Sources 2.6.1.7. Other Data Sources
There are other data sources for log information that must be There are other data sources for log information that must be
collected (as currently collected in IPv4 networks): collected (as currently collected in IPv4 networks):
o historical mapping of IPv6 addresses to users of remote access * historical mappings of IPv6 addresses to users of remote access
VPN; VPN and
o historical mappings of MAC addresses to switch ports in a wired * historical mappings of MAC addresses to switch ports in a wired
network. network.
2.6.2. Use of Collected Data 2.6.2. Use of Collected Data
This section leverages the data collected as described before This section leverages the data collected, as described in
(Section 2.6.1) in order to achieve several security benefits. Section 2.6.1, in order to achieve several security benefits.
Section 9.1 of [RFC7934] contains more details about host tracking. Section 9.1 of [RFC7934] contains more details about host tracking.
2.6.2.1. Forensic and User Accountability 2.6.2.1. Forensic and User Accountability
The forensic use case is when the network operator must locate an The forensic use case is when the network operator must locate an
IPv6 address (and the assocated port, access point/switch, or VPN IPv6 address (and the associated port, access point/switch, or VPN
tunnel) that was present in the network at a certain time or is tunnel) that was present in the network at a certain time or is
currently in the network. currently in the network.
To locate an IPv6 address in an enterprise network where the operator To locate an IPv6 address in an enterprise network where the operator
has control over all resources, the source of information can be the has control over all resources, the source of information can be the
neighbor cache, or, if not found, the DHCP lease file. Then, the Neighbor Cache, or, if not found, the DHCP lease file. Then, the
procedure is: procedure is:
1. Based on the IPv6 prefix of the IPv6 address, find the router(s) 1. based on the IPv6 prefix of the IPv6 address; find one or more
which is(are) used to reach this prefix (assuming that anti- routers that are used to reach this prefix (assuming that anti-
spoofing mechanisms are used) perhaps based on an IPAM. spoofing mechanisms are used), perhaps based on an IPAM.
2. Based on this limited set of routers, on the incident time and on 2. based on this limited set of routers, on the incident time, and
the IPv6 address, retrieve the data-link address from the live on the IPv6 address; retrieve the data-link address from the live
neighbor cache, from the historical neighbor cache data, or from Neighbor Cache, from the historical Neighbor Cache data, or from
SAVI events, or retrieve the data-link address from the DHCP SAVI events, or retrieve the data-link address from the DHCP
lease file (Section 2.6.1.5). lease file (Section 2.6.1.5).
3. Based on the data-link layer address, look-up the switch 3. based on the data-link layer address; look up the switch
interface associated with the data-link layer address. In the interface associated with the data-link layer address. In the
case of wireless LAN with RADIUS accounting (see case of wireless LAN with RADIUS accounting (see
Section 2.6.1.6), the RADIUS log has the mapping between the user Section 2.6.1.6), the RADIUS log has the mapping between the user
identification and the MAC address. If a Configuration identification and the MAC address. If a Configuration
Management Data Base (CMDB) is used, then it can be used to map Management Database (CMDB) is used, then it can be used to map
the data-link layer address to a switch port. the data-link layer address to a switch port.
At the end of the process, the interface of the host originating, or At the end of the process, the interface of the host originating or
the subscriber identity associated with, the activity in question has the subscriber identity associated with the activity in question has
been determined. been determined.
To identify the subscriber of an IPv6 address in a residential To identify the subscriber of an IPv6 address in a residential
Internet Service Provider, the starting point is the DHCP-PD leased Internet Service Provider, the starting point is the DHCP-PD leased
prefix covering the IPv6 address; this prefix can often be linked to prefix covering the IPv6 address; this prefix can often be linked to
a subscriber via the RADIUS log. Alternatively, the Forwarding a subscriber via the RADIUS log. Alternatively, the Forwarding
Information Base (FIB) of the Cable Modem Termination System (CMTS) Information Base (FIB) of the Cable Modem Termination System (CMTS)
or Broadband Network Gateway (BNG) indicates the CPE of the or Broadband Network Gateway (BNG) indicates the Customer Premises
subscriber and the RADIUS log can be used to retrieve the actual Equipment (CPE) of the subscriber and the RADIUS log can be used to
subscriber. retrieve the actual subscriber.
More generally, a mix of the above techniques can be used in most, if More generally, a mix of the above techniques can be used in most, if
not all, networks. not all, networks.
2.6.2.2. Inventory 2.6.2.2. Inventory
RFC 7707 [RFC7707] describes the difficulties for an attacker to scan [RFC7707] describes the difficulties for an attacker to scan an IPv6
an IPv6 network due to the vast number of IPv6 addresses per link network due to the vast number of IPv6 addresses per link (and why in
(and why in some cases it can still be done). While the huge some cases it can still be done). While the huge addressing space
addressing space can sometimes be perceived as a 'protection', it can sometimes be perceived as a 'protection', it also makes the
also makes the inventory task difficult in an IPv6 network while it inventory task difficult in an IPv6 network while it was trivial to
was trivial to do in an IPv4 network (a simple enumeration of all do in an IPv4 network (a simple enumeration of all IPv4 addresses,
IPv4 addresses, followed by a ping and a TCP/UDP port scan). Getting followed by a ping and a TCP/UDP port scan). Getting an inventory of
an inventory of all connected devices is of prime importance for a all connected devices is of prime importance for a secure network
secure network operation. operation.
There are many ways to do an inventory of an IPv6 network. There are many ways to do an inventory of an IPv6 network.
The first technique is to use passive inspection such as IPFIX. The first technique is to use passive inspection, such as IPFIX.
Using exported IPFIX information and extracting the list of all IPv6 Using exported IPFIX information and extracting the list of all IPv6
source addresses allows finding all IPv6 nodes that sent packets source addresses allows finding all IPv6 nodes that sent packets
through a router. This is very efficient but, alas, will not through a router. This is very efficient but, alas, will not
discover silent nodes that never transmitted packets traversing the discover silent nodes that never transmitted packets traversing the
IPFIX target router. Also, it must be noted that link-local IPFIX target router. Also, it must be noted that link-local
addresses will never be discovered by this means. addresses will never be discovered by this means.
The second way is again to use the collected neighbor cache content The second way is again to use the collected Neighbor Cache content
to find all IPv6 addresses in the cache. This process will also to find all IPv6 addresses in the cache. This process will also
discover all link-local addresses. See Section 2.6.1.4. discover all link-local addresses. See Section 2.6.1.4.
Another way that works only for a local network, consists of sending Another way that works only for a local network consists of sending
a ICMP ECHO_REQUEST to the link-local multicast address ff02::1 which an ICMP ECHO_REQUEST to the link-local multicast address ff02::1,
addresses all IPv6 nodes on the network. All nodes should reply to which addresses all IPv6 nodes on the network. All nodes should
this ECHO_REQUEST per [RFC4443]. reply to this ECHO_REQUEST, per [RFC4443].
Other techniques involve obtaining data from DNS, parsing log files, Other techniques involve obtaining data from DNS, parsing log files,
leveraging service discovery such as mDNS [RFC6762] and [RFC6763]. and leveraging service discovery, such as mDNS [RFC6762] [RFC6763].
Enumerating DNS zones, especially looking at reverse DNS records and Enumerating DNS zones, especially looking at reverse DNS records and
CNAMES, is another common method employed by various tools. As CNAMEs, is another common method employed by various tools. As
already mentioned in [RFC7707], this allows an attacker to prune the already mentioned in [RFC7707], this allows an attacker to prune the
IPv6 reverse DNS tree, and hence enumerate it in a feasible time. IPv6 reverse DNS tree and hence enumerate it in a feasible time.
Furthermore, authoritative servers that allow zone transfers (AXFR) Furthermore, authoritative servers that allow zone transfers (i.e.,
may be a further information source. An interesting research paper Authoritative Transfers (AXFRs)) may be a further information source.
has analysed the entropy in various IPv6 addresses: see [ENTROPYIP]. An interesting research paper has analyzed the entropy in various
IPv6 addresses: see [ENTROPYIP].
2.6.2.3. Correlation 2.6.2.3. Correlation
In an IPv4 network, it is easy to correlate multiple logs, for In an IPv4 network, it is easy to correlate multiple logs, for
example to find events related to a specific IPv4 address. A simple example, to find events related to a specific IPv4 address. A simple
Unix grep command is enough to scan through multiple text-based files Unix grep command is enough to scan through multiple text-based files
and extract all lines relevant to a specific IPv4 address. and extract all lines relevant to a specific IPv4 address.
In an IPv6 network, this is slightly more difficult because different In an IPv6 network, this is slightly more difficult because different
character strings can express the same IPv6 address. Therefore, the character strings can express the same IPv6 address. Therefore, the
simple Unix grep command cannot be used. Moreover, an IPv6 node can simple Unix grep command cannot be used. Moreover, an IPv6 node can
have multiple IPv6 addresses. have multiple IPv6 addresses.
In order to do correlation in IPv6-related logs, it is advised to In order to do correlation in IPv6-related logs, it is advised to
have all logs in a format with only canonical IPv6 addresses have all logs in a format with only canonical IPv6 addresses
[RFC5952]. Then, the neighbor cache current (or historical) data set [RFC5952]. Then, the current (or historical) Neighbor Cache data set
must be searched to find the data-link layer address of the IPv6 must be searched to find the data-link layer address of the IPv6
address. Then, the current and historical neighbor cache data sets address. Next, the current and historical Neighbor Cache data sets
must be searched for all IPv6 addresses associated with this data- must be searched for all IPv6 addresses associated with this data-
link layer address to derive the search set. The last step is to link layer address to derive the search set. The last step is to
search in all log files (containing only IPv6 addresses in canonical search in all log files (containing only IPv6 addresses in canonical
format) for any IPv6 addresses in the search set. format) for any IPv6 addresses in the search set.
Moreover, [RFC7934] recommends using multiple IPv6 addresses per Moreover, [RFC7934] recommends using multiple IPv6 addresses per
prefix, so, the correlation must also be done among those multiple prefix, so the correlation must also be done among those multiple
IPv6 addresses, for example by discovering in the NDP cache IPv6 addresses, for example, by discovering all IPv6 addresses
(Section 2.6.1.4) all IPv6 addresses associated with the same MAC associated with the same MAC address and interface in the NDP cache
address and interface. (Section 2.6.1.4).
2.6.2.4. Abnormal Behavior Detection 2.6.2.4. Abnormal Behavior Detection
Abnormal behavior (such as network scanning, spamming, denial-of- Abnormal behavior (such as network scanning, spamming, DoS) can be
service) can be detected in the same way as in an IPv4 network. detected in the same way as in an IPv4 network:
o Sudden increase of traffic detected by interface counter (SNMP) or * a sudden increase of traffic detected by interface counter (SNMP)
by aggregated traffic from IPFIX records [RFC7012]. or by aggregated traffic from IPFIX records [RFC7012],
o Rapid growth of ND cache size. * rapid growth of ND cache size, or
o Change in traffic pattern (number of connections per second, * change in traffic pattern (number of connections per second,
number of connections per host...) observed with the use of IPFIX number of connections per host, etc.) observed with the use of
[RFC7012]. IPFIX [RFC7012].
2.6.3. Summary 2.6.3. Summary
While some data sources (IPFIX, MIB, switch CAM tables, logs, ...) While some data sources (IPFIX, MIB, switch Content Addressable
used in IPv4 are also used in the secure operation of an IPv6 Memory (CAM) tables, logs, etc.) used in IPv4 are also used in the
network, the DHCPv6 lease file is less reliable and the neighbor secure operation of an IPv6 network, the DHCPv6 lease file is less
cache is of prime importance. reliable and the Neighbor Cache is of prime importance.
The fact that there are multiple ways to express the same IPv6 The fact that there are multiple ways to express the same IPv6
address in a character string renders the use of filters mandatory address in a character string renders the use of filters mandatory
when correlation must be done. when correlation must be done.
2.7. Transition/Coexistence Technologies 2.7. Transition/Coexistence Technologies
As it is expected that some networks will not run in a pure IPv6-only As it is expected that some networks will not run in a pure IPv6-only
mode, the different transition mechanisms must be deployed and mode, the different transition mechanisms must be deployed and
operated in a secure way. This section proposes operational operated in a secure way. This section proposes operational
guidelines for the most known and deployed transition techniques. guidelines for the most-known and deployed transition techniques.
[RFC4942] also contains security considerations for transition or [RFC4942] also contains security considerations for transition or
coexistence scenarios. coexistence scenarios.
2.7.1. Dual Stack 2.7.1. Dual Stack
Dual stack is often the first deployment choice for network Dual stack is often the first deployment choice for network
operators. Dual stacking the network offers some advantages over operators. Dual stacking the network offers some advantages over
other transition mechanisms. Firstly, the impact on existing IPv4 other transition mechanisms. Firstly, the impact on existing IPv4
operations is reduced. Secondly, in the absence of tunnels or operations is reduced. Secondly, in the absence of tunnels or
address translation, the IPv4 and IPv6 traffic are native (easier to address translation, the IPv4 and IPv6 traffic are native (easier to
observe and secure) and should have the same network processing observe and secure) and should have the same network processing
(network path, quality of service, ...). Dual stack enables a (network path, quality of service, etc.). Dual stack enables a
gradual termination of the IPv4 operations when the IPv6 network is gradual termination of the IPv4 operations when the IPv6 network is
ready for prime time. On the other hand, the operators have to ready for prime time. On the other hand, the operators have to
manage two network stacks with the added complexities. manage two network stacks with the added complexities.
From an operational security perspective, this now means that the From an operational security perspective, this now means that the
network operator has twice the exposure. One needs to think about network operator has twice the exposure. One needs to think about
protecting both protocols now. At a minimum, the IPv6 portion of a protecting both protocols now. At a minimum, the IPv6 portion of a
dual-stacked network should be consistent with IPv4 from a security dual-stacked network should be consistent with IPv4 from a security
policy point of view. Typically, the following methods are employed policy point of view. Typically, the following methods are employed
to protect IPv4 networks at the edge or security perimeter: to protect IPv4 networks at the edge or security perimeter:
o ACLs to permit or deny traffic; * ACLs to permit or deny traffic,
o Firewalls with stateful packet inspection; * firewalls with stateful packet inspection, and
o Application firewalls inspecting the application flows. * application firewalls inspecting the application flows.
It is recommended that these ACLs and/or firewalls be additionally It is recommended that these ACLs and/or firewalls be additionally
configured to protect IPv6 communications. The enforced IPv6 configured to protect IPv6 communications. The enforced IPv6
security must be congruent with the IPv4 security policy, otherwise security must be congruent with the IPv4 security policy; otherwise,
the attacker will use the protocol version having the more relaxed the attacker will use the protocol version that has the more relaxed
security policy. Maintaining the congruence between security security policy. Maintaining the congruence between security
policies can be challenging (especially over time); it is recommended policies can be challenging (especially over time); it is recommended
to use a firewall or an ACL manager that is dual-stack, i.e., a to use a firewall or an ACL manager that is dual stack, i.e., a
system that can apply a single ACL entry to a mixed group of IPv4 and system that can apply a single ACL entry to a mixed group of IPv4 and
IPv6 addresses. IPv6 addresses.
Application firewalls work at the application layer and are oblivious Application firewalls work at the application layer and are oblivious
to the IP version, i.e., they work as well for IPv6 as for IPv4 and to the IP version, i.e., they work as well for IPv6 as for IPv4 and
the same application security policy will work for both protocol the same application security policy will work for both protocol
versions. versions.
Also, given the end-to-end connectivity that IPv6 provides, it is Also, given the end-to-end connectivity that IPv6 provides, it is
recommended that hosts be fortified against threats. General device recommended that hosts be fortified against threats. General device
hardening guidelines are provided in Section 2.8. hardening guidelines are provided in Section 2.8.
For many years, all host operating systems have IPv6 enabled by For many years, all host operating systems have IPv6 enabled by
default, so, it is possible even in an 'IPv4-only' network to attack default, so it is possible even in an 'IPv4-only' network to attack
layer-2 adjacent victims via their IPv6 link-local address or via a L2-adjacent victims via their IPv6 link-local address or via a global
global IPv6 address when the attacker provides rogue RAs or a rogue IPv6 address when the attacker provides rogue RAs or a rogue DHCPv6
DHCPv6 service. service.
[RFC7123] discusses the security implications of native IPv6 support [RFC7123] discusses the security implications of native IPv6 support
and IPv6 transition/coexistence technologies on "IPv4-only" networks and IPv6 transition/coexistence technologies on 'IPv4-only' networks
and describes possible mitigations for the aforementioned issues. and describes possible mitigations for the aforementioned issues.
2.7.2. Encapsulation Mechanisms 2.7.2. Encapsulation Mechanisms
There are many tunnels used for specific use cases. Except when There are many tunnels used for specific use cases. Except when
protected by IPsec [RFC4301] or alternative tunnel encryption protected by IPsec [RFC4301] or alternative tunnel encryption
methods, all those tunnels have a number of security issues as methods, all those tunnels have a number of security issues, as
described in RFC 6169 [RFC6169]; described in [RFC6169]:
o tunnel injection: a malevolent actor knowing a few pieces of tunnel injection:
information (for example the tunnel endpoints and the A malevolent actor knowing a few pieces of information (for
encapsulation protocol) can forge a packet which looks like a example, the tunnel endpoints and the encapsulation protocol) can
legitimate and valid encapsulated packet that will gladly be forge a packet that looks like a legitimate and valid encapsulated
accepted by the destination tunnel endpoint. This is a specific packet that will gladly be accepted by the destination tunnel
case of spoofing; endpoint. This is a specific case of spoofing.
o traffic interception: no confidentiality is provided by the tunnel traffic interception:
protocols (without the use of IPsec or alternative encryption No confidentiality is provided by the tunnel protocols (without
methods), therefore anybody on the tunnel path can intercept the the use of IPsec or alternative encryption methods); therefore,
traffic and have access to the clear-text IPv6 packet; combined anybody on the tunnel path can intercept the traffic and have
with the absence of authentication, an on-path attack can also be access to the cleartext IPv6 packet. Combined with the absence of
mounted; authentication, an on-path attack can also be mounted.
o service theft: as there is no authorization, even a non-authorized service theft:
user can use a tunnel relay for free (this is a specific case of As there is no authorization, even an unauthorized user can use a
tunnel injection); tunnel relay for free (this is a specific case of tunnel
injection).
o reflection attack: another specific use case of tunnel injection reflection attack:
where the attacker injects packets with an IPv4 destination Another specific use case of tunnel injection where the attacker
address not matching the IPv6 address causing the first tunnel injects packets with an IPv4 destination address not matching the
endpoint to re-encapsulate the packet to the destination... Hence, IPv6 address causing the first tunnel endpoint to re-encapsulate
the final IPv4 destination will not see the original IPv4 address the packet to the destination. Hence, the final IPv4 destination
but only the IPv4 address of the relay router. will not see the original IPv4 address but only the IPv4 address
of the relay router.
o bypassing security policy: if a firewall or an Intrusion bypassing security policy:
Prevention System (IPS) is on the path of the tunnel, then it may If a firewall or an Intrusion Prevention System (IPS) is on the
neither inspect nor detect malevolent IPv6 traffic transmitted path of the tunnel, then it may neither inspect nor detect
over the tunnel. malevolent IPv6 traffic transmitted over the tunnel.
To mitigate the bypassing of security policies, it is often To mitigate the bypassing of security policies, it is often
recommended to block all automatic tunnels in default OS recommended to block all automatic tunnels in default OS
configuration (if they are not required) by denying IPv4 packets configuration (if they are not required) by denying IPv4 packets
matching: matching:
o IP protocol 41: this will block ISATAP (Section 2.7.2.2), 6to4 IP protocol 41: This will block Intra-Site Automatic Tunnel
(Section 2.7.2.7), 6rd (Section 2.7.2.3), as well as, 6in4 Addressing Protocol (ISATAP) (Section 2.7.2.2), 6to4
(Section 2.7.2.1) tunnels; (Section 2.7.2.7), 6rd (Section 2.7.2.3), and 6in4
(Section 2.7.2.1) tunnels.
o IP protocol 47: this will block GRE (Section 2.7.2.1) tunnels; IP protocol 47: This will block GRE (Section 2.7.2.1) tunnels.
o UDP port 3544: this will block the default encapsulation of Teredo UDP port 3544: This will block the default encapsulation of Teredo
(Section 2.7.2.8) tunnels. (Section 2.7.2.8) tunnels.
Ingress filtering [RFC2827] should also be applied on all tunnel Ingress filtering [RFC2827] should also be applied on all tunnel
endpoints if applicable to prevent IPv6 address spoofing. endpoints, if applicable, to prevent IPv6 address spoofing.
The reflection attack cited above should also be prevented by using The reflection attack cited above should also be prevented by using
an IPv6 ACL preventing the hair pinning of the traffic. an IPv6 ACL preventing the hair pinning of the traffic.
As several of the tunnel techniques share the same encapsulation As several of the tunnel techniques share the same encapsulation
(i.e., IPv4 protocol 41) and embed the IPv4 address in the IPv6 (i.e., IPv4 protocol 41) and embed the IPv4 address in the IPv6
address, there are a set of well-known looping attacks described in address, there are a set of well-known looping attacks described in
RFC 6324 [RFC6324]. This RFC also proposes mitigation techniques. [RFC6324]. This RFC also proposes mitigation techniques.
2.7.2.1. Site-to-Site Static Tunnels 2.7.2.1. Site-to-Site Static Tunnels
Site-to-site static tunnels are described in RFC 2529 [RFC2529] and Site-to-site static tunnels are described in [RFC2529] and in GRE
in GRE [RFC2784]. As the IPv4 endpoints are statically configured [RFC2784]. As the IPv4 endpoints are statically configured and are
and are not dynamic, they are slightly more secure (bi-directional not dynamic, they are slightly more secure (bidirectional service
service theft is mostly impossible) but traffic interception and theft is mostly impossible), but traffic interception and tunnel
tunnel injection are still possible. Therefore, the use of IPsec injection are still possible. Therefore, the use of IPsec [RFC4301]
[RFC4301] in transport mode to protect the encapsulated IPv4 packets in transport mode to protect the encapsulated IPv4 packets is
is recommended for those tunnels. Alternatively, IPsec in tunnel recommended for those tunnels. Alternatively, IPsec in tunnel mode
mode can be used to transport IPv6 traffic over a non-trusted IPv4 can be used to transport IPv6 traffic over an untrusted IPv4 network.
network.
2.7.2.2. ISATAP 2.7.2.2. ISATAP
ISATAP tunnels [RFC5214] are mainly used within a single ISATAP tunnels [RFC5214] are mainly used within a single
administrative domain and to connect a single IPv6 host to the IPv6 administrative domain and to connect a single IPv6 host to the IPv6
network. This often implies that those systems are usually managed network. This often implies that those systems are usually managed
by a single entity; therefore, audit trail and strict anti-spoofing by a single entity; therefore, audit trail and strict anti-spoofing
are usually possible and this raises the overall security. Even if are usually possible, and this raises the overall security. Even if
ISATAP is no more often used, its security issues are relevant per ISATAP is no more often used, its security issues are relevant, per
[KRISTOFF]. [KRISTOFF].
Special care must be taken to avoid a looping attack by implementing Special care must be taken to avoid a looping attack by implementing
the measures of [RFC6324] and [RFC6964] (especially the section 3.6). the measures of [RFC6324] and [RFC6964] (especially in Section 3.6).
IPsec [RFC4301] in transport or tunnel mode can be used to secure the IPsec [RFC4301] in transport or tunnel mode can be used to secure the
IPv4 ISATAP traffic to provide IPv6 traffic confidentiality and IPv4 ISATAP traffic to provide IPv6 traffic confidentiality and
prevent service theft. prevent service theft.
2.7.2.3. 6rd 2.7.2.3. 6rd
While 6rd tunnels share the same encapsulation as 6to4 tunnels While 6rd tunnels share the same encapsulation as 6to4 tunnels
(Section 2.7.2.7), they are designed to be used within a single SP (Section 2.7.2.7), they are designed to be used within a single SP
domain, in other words, they are deployed in a more constrained domain; in other words, they are deployed in a more constrained
environment (e.g., anti-spoofing, protocol 41 filtering at the edge) environment (e.g., anti-spoofing, protocol 41 filtering at the edge)
than 6to4 tunnels and have few security issues other than lack of than 6to4 tunnels and have few security issues other than lack of
confidentiality. The security considerations (Section 12) of confidentiality. The security considerations in Section 12 of
[RFC5969] describes how to secure 6rd tunnels. [RFC5969] describes how to secure 6rd tunnels.
IPsec [RFC4301] for the transported IPv6 traffic can be used if IPsec [RFC4301] for the transported IPv6 traffic can be used if
confidentiality is important. confidentiality is important.
2.7.2.4. 6PE, 6VPE, and LDPv6 2.7.2.4. 6PE, 6VPE, and LDPv6
Organizations using MPLS in their core can also use 6PE [RFC4798] and Organizations using MPLS in their core can also use IPv6 Provider
6VPE [RFC4659] to enable IPv6 access over MPLS. As 6PE and 6VPE are Edge (6PE) [RFC4798] and IPv6 Virtual Private Extension (6VPE)
[RFC4659] to enable IPv6 access over MPLS. As 6PE and 6VPE are
really similar to BGP/MPLS IP VPNs described in [RFC4364], the really similar to BGP/MPLS IP VPNs described in [RFC4364], the
security properties of these networks are also similar to those security properties of these networks are also similar to those
described in [RFC4381] (please note that this RFC may resemble a described in [RFC4381] (please note that this RFC may resemble a
published IETF work but it is not based on an IETF review and the published IETF work, but it is not based on an IETF review and the
IETF disclaims any knowledge of the fitness of this RFC for any IETF disclaims any knowledge of the fitness of this RFC for any
purpose). They rely on: purpose). They rely on:
o Address space, routing, and traffic separation with the help of * address space, routing, and traffic separation with the help of
VRFs (only applicable to 6VPE); VRFs (only applicable to 6VPE);
o Hiding the IPv4 core, hence removing all attacks against * hiding the IPv4 core, hence, removing all attacks against
P-routers; P-routers; and
o Securing the routing protocol between CE and PE; in the case of * securing the routing protocol between Customer Edge (CE) and
6PE and 6VPE, link-local addresses (see [RFC7404]) can be used and Provider Edge (PE); in the case of 6PE and 6VPE, link-local
as these addresses cannot be reached from outside of the link, the addresses (see [RFC7404]) can be used, and, as these addresses
security of 6PE and 6VPE is even higher than an IPv4 BGP/MPLS IP cannot be reached from outside of the link, the security of 6PE
VPN. and 6VPE is even higher than an IPv4 BGP/MPLS IP VPN.
LDPv6 itself does not induce new risks, see also [RFC7552]. LDPv6 itself does not induce new risks; see [RFC7552].
2.7.2.5. DS-Lite 2.7.2.5. DS-Lite
DS-lite is also a translation mechanism and is therefore analyzed Dual-Stack Lite (DS-Lite) is also a translation mechanism and is
further (Section 2.7.3.3) in this document as it includes IPv4 NAPT. therefore analyzed further (Section 2.7.3.3) in this document, as it
includes IPv4 NAPT.
2.7.2.6. Mapping of Address and Port 2.7.2.6. Mapping of Address and Port
With the encapsulation and translation versions of mapping of Address With the encapsulation and translation versions of Mapping of Address
and Port (MAP) (MAP-E [RFC7597] and MAP-T [RFC7599]), the access and Port (MAP) -- abbreviated MAP-E [RFC7597] and MAP-T [RFC7599] --
network is purely an IPv6 network and MAP protocols are used to the access network is purely an IPv6 network, and MAP protocols are
provide IPv4 hosts on the subscriber network access to IPv4 hosts on used to provide IPv4 hosts on the subscriber network access to IPv4
the Internet. The subscriber router does stateful operations in hosts on the Internet. The subscriber router does stateful
order to map all internal IPv4 addresses and layer-4 ports to the operations in order to map all internal IPv4 addresses and Layer 4
IPv4 address and the set of layer-4 ports received through the MAP ports to the IPv4 address and the set of Layer 4 ports received
configuration process. The SP equipment always does stateless through the MAP configuration process. The SP equipment always does
operations (either decapsulation or stateless translation). stateless operations (either decapsulation or stateless translation).
Therefore, as opposed to Section 2.7.3.3, there is no state- Therefore, as opposed to Section 2.7.3.3, there is no state
exhaustion DoS attack against the SP equipment because there is no exhaustion DoS attack against the SP equipment because there is no
state and there is no operation caused by a new layer-4 connection state and there is no operation caused by a new Layer 4 connection
(no logging operation). (no logging operation).
The SP MAP equipment should implement all the security considerations The SP MAP equipment should implement all the security considerations
of [RFC7597]; notably, ensuring that the mapping of the IPv4 address of [RFC7597], notably ensuring that the mapping of the IPv4 address
and port are consistent with the configuration. As MAP has a and port are consistent with the configuration. As MAP has a
predictable IPv4 address and port mapping, the audit logs are easier predictable IPv4 address and port mapping, the audit logs are easier
to use as there is a clear mapping between the IPv6 address and the to use, as there is a clear mapping between the IPv6 address and the
IPv4 address and ports. IPv4 address and ports.
2.7.2.7. 6to4 2.7.2.7. 6to4
In [RFC3056]; 6to4 tunnels require a public routable IPv4 address in In [RFC3056], 6to4 tunnels require a public-routable IPv4 address in
order to work correctly. They can be used to provide either single order to work correctly. They can be used to provide either single
IPv6 host connectivity to the IPv6 Internet or multiple IPv6 networks IPv6 host connectivity to the IPv6 Internet or multiple IPv6 networks
connectivity to the IPv6 Internet. The 6to4 relay was historically connectivity to the IPv6 Internet. The 6to4 relay was historically
the anycast address defined in [RFC3068] which has been deprecated by the anycast address defined in [RFC3068], which has been deprecated
[RFC7526] and is no longer used by recent Operating Systems. Some by [RFC7526] and is no longer used by recent Operating Systems. Some
security considerations are explained in [RFC3964]. security considerations are explained in [RFC3964].
[RFC6343] points out that if an operator provides well-managed [RFC6343] points out that if an operator provides well-managed
servers and relays for 6to4, non-encapsulated IPv6 packets will pass servers and relays for 6to4, nonencapsulated IPv6 packets will pass
through well-defined points (the native IPv6 interfaces of those through well-defined points (the native IPv6 interfaces of those
servers and relays) at which security mechanisms may be applied. servers and relays) at which security mechanisms may be applied.
Client usage of 6to4 by default is now discouraged, and significant Client usage of 6to4 by default is now discouraged, and significant
precautions are needed to avoid operational problems. precautions are needed to avoid operational problems.
2.7.2.8. Teredo 2.7.2.8. Teredo
Teredo tunnels [RFC4380] are mainly used in a residential environment Teredo tunnels [RFC4380] are mainly used in a residential environment
because Teredo easily traverses an IPv4 NAPT device thanks to its UDP because Teredo easily traverses an IPv4 NAPT device thanks to its UDP
encapsulation. Teredo tunnels connect a single host to the IPv6 encapsulation. Teredo tunnels connect a single host to the IPv6
Internet. Teredo shares the same issues as other tunnels: no Internet. Teredo shares the same issues as other tunnels: no
authentication, no confidentiality, possible spoofing and reflection authentication, no confidentiality, possible spoofing, and reflection
attacks. attacks.
IPsec [RFC4301] for the transported IPv6 traffic is recommended. IPsec [RFC4301] for the transported IPv6 traffic is recommended.
The biggest threat to Teredo is probably for an IPv4-only network as The biggest threat to Teredo is probably for an IPv4-only network, as
Teredo has been designed to easily traverse IPv4 NAT-PT devices which Teredo has been designed to easily traverse IPv4 NAT-PT devices,
are quite often co-located with a stateful firewall. Therefore, if which are quite often co-located with a stateful firewall.
the stateful IPv4 firewall allows unrestricted UDP outbound and Therefore, if the stateful IPv4 firewall allows unrestricted UDP
accepts the return UDP traffic, then Teredo actually punches a hole outbound and accepts the return UDP traffic, then Teredo actually
in this firewall for all IPv6 traffic to the Internet and from the punches a hole in this firewall for all IPv6 traffic to and from the
Internet. Host policies can be deployed to block Teredo in an Internet. Host policies can be deployed to block Teredo in an
IPv4-only network in order to avoid this firewall bypass. On the IPv4-only network in order to avoid this firewall bypass. On the
IPv4 firewall all outbound UDP should be blocked except for the IPv4 firewall, all outbound UDPs should be blocked except for the
commonly used services (e.g., port 53 for DNS, port 123 for NTP, port commonly used services (e.g., port 53 for DNS, port 123 for NTP, port
443 for QUIC, port 500 for IKE, port 3478 for STUN, etc.). 443 for QUIC, port 500 for Internet Key Exchange Protocol (IKE), port
3478 for Session Traversal Utilities for NAT (STUN), etc.).
Teredo is now hardly ever used and no longer enabled by default in Teredo is now hardly ever used and no longer enabled by default in
most environments, so it is less of a threat, however, special most environments so it is less of a threat; however, special
consideration must be taken in cases when devices with older or non- consideration must be made in cases when devices with older or
updated operating systems may be present and by default were running operating systems that have not been updated may be present and by
Teredo. default were running Teredo.
2.7.3. Translation Mechanisms 2.7.3. Translation Mechanisms
Translation mechanisms between IPv4 and IPv6 networks are alternate Translation mechanisms between IPv4 and IPv6 networks are alternate
coexistence strategies while networks transition to IPv6. While a coexistence strategies while networks transition to IPv6. While a
framework is described in [RFC6144], the specific security framework is described in [RFC6144], the specific security
considerations are documented with each individual mechanism. For considerations are documented with each individual mechanism. For
the most part, they specifically mention interference with IPsec or the most part, they specifically mention interference with IPsec or
DNSSEC deployments, how to mitigate spoofed traffic, and what some DNSSEC deployments, how to mitigate spoofed traffic, and what some
effective filtering strategies may be. effective filtering strategies may be.
While not really a transition mechanism to IPv6, this section also While not really a transition mechanism to IPv6, this section also
includes the discussion about the use of heavy IPv4-to-IPv4 network includes the discussion about the use of heavy IPv4-to-IPv4 network
address and port translation to prolong the life of IPv4-only addresses and port translation to prolong the life of IPv4-only
networks. networks.
2.7.3.1. Carrier-Grade NAT (CGN) 2.7.3.1. Carrier-Grade NAT (CGN)
Carrier-Grade NAT (CGN), also called NAT444 CGN or Large Scale NAT Carrier-Grade NAT (CGN), also called NAT444 CGN or Large-Scale NAT
(LSN) or SP NAT is described in [RFC6264] and is utilized as an (LSN) or SP NAT, is described in [RFC6264] and is utilized as an
interim measure to extend the use of IPv4 in a large service provider interim measure to extend the use of IPv4 in a large service provider
network until the provider can deploy an effective IPv6 solution. network until the provider can deploy an effective IPv6 solution.
[RFC6598] requested a specific IANA allocated /10 IPv4 address block [RFC6598] requested a specific IANA-allocated /10 IPv4 address block
to be used as address space shared by all access networks using CGN. to be used as address space shared by all access networks using CGN.
This has been allocated as 100.64.0.0/10. This has been allocated as 100.64.0.0/10.
Section 13 of [RFC6269] lists some specific security-related issues Section 13 of [RFC6269] lists some specific security-related issues
caused by large scale address sharing. The Security Considerations caused by large-scale address sharing. The Security Considerations
section of [RFC6598] also lists some specific mitigation techniques section of [RFC6598] also lists some specific mitigation techniques
for potential misuse of shared address space. Some Law Enforcement for potential misuse of shared address space. Some law enforcement
Agencies have identified CGN as impeding their cyber-crime agencies have identified CGN as impeding their cybercrime
investigations (for example Europol press release on CGN investigations (for example, see the Europol press release on CGN
[europol-cgn]). Many translation techniques (NAT64, DS-lite, ...) [europol-cgn]). Many translation techniques (NAT64, DS-Lite, etc.)
have the same security issues as CGN when one part of the connection have the same security issues as CGN when one part of the connection
is IPv4-only. is IPv4 only.
[RFC6302] has recommendations for Internet-facing servers to also log [RFC6302] has recommendations for Internet-facing servers to also log
the source TCP or UDP ports of incoming connections in an attempt to the source TCP or UDP ports of incoming connections in an attempt to
help identify the users behind such a CGN. help identify the users behind such a CGN.
[RFC7422] suggests the use of deterministic address mapping in order [RFC7422] suggests the use of deterministic address mapping in order
to reduce logging requirements for CGN. The idea is to have a known to reduce logging requirements for CGN. The idea is to have a known
algorithm for mapping the internal subscriber to/from public TCP and algorithm for mapping the internal subscriber to/from public TCP and
UDP ports. UDP ports.
[RFC6888] lists common requirements for CGNs. [RFC6967] analyzes [RFC6888] lists common requirements for CGNs. [RFC6967] analyzes
some solutions to enforce policies on misbehaving nodes when address some solutions to enforce policies on misbehaving nodes when address
sharing is used. [RFC7857] also updates the NAT behavioral sharing is used. [RFC7857] also updates the NAT behavioral
requirements. requirements.
2.7.3.2. NAT64/DNS64 and 464XLAT 2.7.3.2. NAT64/DNS64 and 464XLAT
Stateful NAT64 translation [RFC6146] allows IPv6-only clients to Stateful NAT64 translation [RFC6146] allows IPv6-only clients to
contact IPv4 servers using unicast UDP, TCP, or ICMP. It can be used contact IPv4 servers using unicast UDP, TCP, or ICMP. It can be used
in conjunction with DNS64 [RFC6147], a mechanism which synthesizes in conjunction with DNS64 [RFC6147], a mechanism that synthesizes
AAAA records from existing A records. There is also a stateless AAAA records from existing A records. There is also a stateless
NAT64 [RFC7915], which has similar security aspects but with the NAT64 [RFC7915], which has similar security aspects but with the
added benefit of being stateless, so, less prone to a state added benefit of being stateless and is thereby less prone to a state
exhaustion attack. exhaustion attack.
The Security Consideration sections of [RFC6146] and [RFC6147] list The Security Consideration sections of [RFC6146] and [RFC6147] list
the comprehensive issues; in section 8 of [RFC6147] there are some the comprehensive issues; in Section 8 of [RFC6147], there are some
considerations on the interaction between NAT64 and DNSSEC. A considerations on the interaction between NAT64 and DNSSEC. A
specific issue with the use of NAT64 is that it will interfere with specific issue with the use of NAT64 is that it will interfere with
most IPsec deployments unless UDP encapsulation is used. most IPsec deployments unless UDP encapsulation is used.
Another translation mechanism relying on a combination of stateful Another translation mechanism relying on a combination of stateful
and stateless translation, 464XLAT [RFC6877], can be used to do host and stateless translation, 464XLAT [RFC6877], can be used to do a
local translation from IPv4 to IPv6 and a network provider host-local translation from IPv4 to IPv6 and a network provider
translation from IPv6 to IPv4, i.e., giving IPv4-only application translation from IPv6 to IPv4, i.e., giving IPv4-only application
access to an IPv4-only server over an IPv6-only network. 464XLAT access to an IPv4-only server over an IPv6-only network. 464XLAT
shares the same security considerations as NAT64 and DNS64, however shares the same security considerations as NAT64 and DNS64; however,
it can be used without DNS64, avoiding the DNSSEC implications. it can be used without DNS64, avoiding the DNSSEC implications.
2.7.3.3. DS-Lite 2.7.3.3. DS-Lite
Dual-Stack Lite (DS-Lite) [RFC6333] is a transition technique that Dual-Stack Lite (DS-Lite) [RFC6333] is a transition technique that
enables a service provider to share IPv4 addresses among customers by enables a service provider to share IPv4 addresses among customers by
combining two well-known technologies: IP in IP (IPv4-in-IPv6) and combining two well-known technologies: IP in IP (IPv4-in-IPv6) and
IPv4 NAPT. IPv4 NAPT.
Security considerations with respect to DS-Lite mainly revolve around Security considerations, with respect to DS-Lite, mainly revolve
logging data, preventing DoS attacks from rogue devices (as the around logging data, preventing DoS attacks from rogue devices (as
Address Family Translation Router (AFTR) [RFC6333] function is the Address Family Translation Router (AFTR) [RFC6333] function is
stateful) and restricting service offered by the AFTR only to stateful), and restricting service offered by the AFTR only to
registered customers. registered customers.
Section 11 of [RFC6333] and section 2 of [RFC7785] describe important Section 11 of [RFC6333] and Section 2 of [RFC7785] describe important
security issues associated with this technology. security issues associated with this technology.
2.8. General Device Hardening 2.8. General Device Hardening
With almost all devices being IPv6 enabled by default and with many With almost all devices being IPv6 enabled by default and with many
end points having IPv6 connectivity to the Internet, it is critical endpoints having IPv6 connectivity to the Internet, it is critical to
to also harden those devices against attacks over IPv6. also harden those devices against attacks over IPv6.
The ame techniques used to protect devices against attack over IPv4 The same techniques used to protect devices against attacks over IPv4
should be used for IPv6 and should include, but not limited to: should be used for IPv6 and should include but are not limited to:
o Restrict device access to authorized individuals * restricting device access to authorized individuals;
o Monitor and audit access to the device * monitoring and auditing access to the device;
o Turn off any unused services on the end node * turning off any unused services on the end node
o Understand which IPv6 addresses are being used to source traffic * understanding which IPv6 addresses are being used to source
and change defaults if necessary traffic and changing defaults if necessary;
o Use cryptographically protected protocols for device management * using cryptographically protected protocols for device management
(SCP, SNMPv3, SSH, TLS, etc.) (Secure Copy Protocol (SCP), SNMPv3, SSH, TLS, etc.);
o Use host firewall capabilities to control traffic that gets * using host firewall capabilities to control traffic that gets
processed by upper-layer protocols processed by upper-layer protocols;
o apply firmware, OS and application patches/upgrades to the devices * applying firmware, OS, and application patches/upgrades to the
in a timely manner devices in a timely manner;
o use multi-factor credentials to authenticate to devices * using multifactor credentials to authenticate to devices; and
o Use virus scanners to detect malicious programs * using virus scanners to detect malicious programs.
3. Enterprises Specific Security Considerations 3. Enterprises-Specific Security Considerations
Enterprises [RFC7381] generally have robust network security policies Enterprises [RFC7381] generally have robust network security policies
in place to protect existing IPv4 networks. These policies have been in place to protect existing IPv4 networks. These policies have been
distilled from years of experiential knowledge of securing IPv4 distilled from years of experiential knowledge of securing IPv4
networks. At the very least, it is recommended that enterprise networks. At the very least, it is recommended that enterprise
networks have parity between their security policies for both networks have parity between their security policies for both
protocol versions. This section also applies to the enterprise part protocol versions. This section also applies to the enterprise part
of all SP networks, i.e., the part of the network where the SP of all SP networks, i.e., the part of the network where the SP
employees are connected. employees are connected.
Security considerations in the enterprise can be broadly categorized Security considerations in the enterprise can be broadly categorized
into two groups: External and Internal. into two groups: external and internal.
3.1. External Security Considerations 3.1. External Security Considerations
The external aspect deals with providing security at the edge or The external aspect deals with providing security at the edge or
perimeter of the enterprise network where it meets the service perimeter of the enterprise network where it meets the service
provider's network. This is commonly achieved by enforcing a provider's network. This is commonly achieved by enforcing a
security policy either by implementing dedicated firewalls with security policy, either by implementing dedicated firewalls with
stateful packet inspection or a router with ACLs. A common default stateful packet inspection or a router with ACLs. A common default
IPv4 policy on firewalls that could easily be ported to IPv6 is to IPv4 policy on firewalls that could easily be ported to IPv6 is to
allow all traffic outbound while only allowing specific traffic, such allow all traffic outbound while only allowing specific traffic, such
as established sessions, inbound (see also [RFC6092]). Section 3.2 as established sessions, inbound (see [RFC6092]). Section 3.2 of
of [RFC7381] also provides similar recommendations. [RFC7381] also provides similar recommendations.
Here are a few more things that could enhance the default policy: Here are a few more things that could enhance the default policy:
o Filter internal-use IPv6 addresses at the perimeter, this will * Filter internal-use IPv6 addresses at the perimeter; this will
also mitigate the vulnerabilities listed in [RFC7359] also mitigate the vulnerabilities listed in [RFC7359].
o Discard packets from and to bogon and reserved space, see also * Discard packets from and to bogon and reserved space; see [CYMRU]
[CYMRU] and [RFC8190] and [RFC8190].
o Accept certain ICMPv6 messages to allow proper operation of ND and * Accept certain ICMPv6 messages to allow proper operation of ND and
PMTUD, see also [RFC4890] or [REY_PF] for hosts Path MTU Discovery (PMTUD); see [RFC4890] or [REY_PF] for hosts.
o Based on the use of the network, filter specific extension headers * Based on the use of the network, filter specific extension headers
by accepting only the required ones (permit list approach) such as by accepting only the required ones (permit list approach), such
ESP, AH, and not forgetting the required transport layers: ICMP, as ESP, AH, and not forgetting the required transport layers:
TCP, UDP, ... This filtering should be done where applicable at ICMP, TCP, UDP, etc. This filtering should be done where
the edge and possibly inside the perimeter; see also applicable at the edge and possibly inside the perimeter; see
[I-D.ietf-opsec-ipv6-eh-filtering] [IPV6-EH-FILTERING].
o Filter packets having an illegal IPv6 headers chain at the * Filter packets having an illegal IPv6 header chain at the
perimeter (and if possible, inside the network as well), see perimeter (and, if possible, inside the network as well); see
Section 2.2 Section 2.2.
o Filter unneeded services at the perimeter * Filter unneeded services at the perimeter.
o Implement ingress and egress anti-spoofing in the forwarding and * Implement ingress and egress anti-spoofing in the forwarding and
control planes, see [RFC2827] and [RFC3704] control planes; see [RFC2827] and [RFC3704].
o Implement appropriate rate-limiters and control-plane policers * Implement appropriate rate-limiters and control plane policers
based on traffic baselines based on traffic baselines.
Having global IPv6 addresses on all the enterprise sites is different Having global IPv6 addresses on all the enterprise sites is different
than in IPv4 where [RFC1918] addresses are often used internally and than in IPv4, where [RFC1918] addresses are often used internally and
not routed over the Internet. [RFC7359] and [WEBER_VPN] explain that not routed over the Internet. [RFC7359] and [WEBER_VPN] explain that
without careful design, there could be IPv6 leakages from layer-3 without careful design, there could be IPv6 leakages from Layer 3
VPNs. VPNs.
3.2. Internal Security Considerations 3.2. Internal Security Considerations
The internal aspect deals with providing security inside the The internal aspect deals with providing security inside the
perimeter of the network, including end hosts. Internal networks of perimeter of the network, including end hosts. Internal networks of
enterprises are often different: University campus, wireless guest enterprises are often different, e.g., University campus, wireless
access, ... so there is no "one size fits all" recommendation. guest access, etc., so there is no "one size fits all"
recommendation.
The most significant concerns here are related to Neighbor Discovery. The most significant concerns here are related to Neighbor Discovery.
At the network level, it is recommended that all security At the network level, it is recommended that all security
considerations discussed in Section 2.3 be reviewed carefully and the considerations discussed in Section 2.3 be reviewed carefully and the
recommendations be considered in-depth as well. Section 4.1 of recommendations be considered in-depth as well. Section 4.1 of
[RFC7381] also provides some recommendations. [RFC7381] also provides some recommendations.
As mentioned in Section 2.7.2, care must be taken when running As mentioned in Section 2.7.2, care must be taken when running
automated IPv6-in-IPv4 tunnels. automated IPv6-in-IPv4 tunnels.
When site-to-site VPNs are used it should be kept in mind that, given When site-to-site VPNs are used, it should be kept in mind that,
the global scope of IPv6 global addresses as opposed to the common given the global scope of IPv6 global addresses as opposed to the
use of IPv4 private address space [RFC1918], sites might be able to common use of IPv4 private address space [RFC1918], sites might be
communicate with each other over the Internet even when the VPN able to communicate with each other over the Internet even when the
mechanism is not available and hence no traffic encryption is VPN mechanism is not available. Hence, no traffic encryption is
performed and traffic could be injected from the Internet into the performed and traffic could be injected from the Internet into the
site, see [WEBER_VPN]. It is recommended to filter at Internet site; see [WEBER_VPN]. It is recommended to filter at Internet
connection(s) packets having a source or destination address connection(s) packets having a source or destination address
belonging to the site internal prefix(es); this should be done for belonging to the site internal prefix or prefixes; this should be
ingress and egress traffic. done for ingress and egress traffic.
Hosts need to be hardened directly through security policy to protect Hosts need to be hardened directly through security policy to protect
against security threats. The host firewall default capabilities against security threats. The host firewall default capabilities
have to be clearly understood. In some cases, 3rd party firewalls have to be clearly understood. In some cases, third-party firewalls
have no IPv6 support whereas the native firewall installed by default have no IPv6 support, whereas the native firewall installed by
has IPv6 support. General device hardening guidelines are provided default has IPv6 support. General device hardening guidelines are
in Section 2.8. provided in Section 2.8.
It should also be noted that many hosts still use IPv4 for It should also be noted that many hosts still use IPv4 for
transporting logs for RADIUS, DIAMETER, TACACS+, SYSLOG, etc. transporting logs for RADIUS, DIAMETER, TACACS+, syslog, etc.
Operators cannot rely on an IPv6-only security policy to secure such Operators cannot rely on an IPv6-only security policy to secure such
protocols that are still using IPv4. protocols that are still using IPv4.
4. Service Providers Security Considerations 4. Service Provider Security Considerations
4.1. BGP 4.1. BGP
The threats and mitigation techniques are identical between IPv4 and The threats and mitigation techniques are identical between IPv4 and
IPv6. Broadly speaking they are: IPv6. Broadly speaking, they are:
o Authenticating the TCP session; * authenticating the TCP session;
o TTL security (which becomes hop-limit security in IPv6) as * TTL security (which becomes hop-limit security in IPv6), as in
[RFC5082]; [RFC5082];
o bogon AS filtering, see [CYMRU]; * bogon AS filtering; see [CYMRU]; and
o Prefix filtering. * prefix filtering.
These are explained in more detail in Section 2.5. Also, the These are explained in more detail in Section 2.5. Also, the
recommendations of [RFC7454] should be considered. recommendations of [RFC7454] should be considered.
4.1.1. Remote Triggered Black Hole Filtering (RTBH) 4.1.1. Remote Triggered Black Hole Filtering
RTBH [RFC5635] works identically in IPv4 and IPv6. IANA has A Remote Triggered Black Hole (RTBH) [RFC5635] works identically in
allocated the 100::/64 prefix to be used as the discard prefix IPv4 and IPv6. IANA has allocated the 100::/64 prefix to be used as
[RFC6666] the discard prefix [RFC6666].
4.2. Transition/Coexistence Mechanism 4.2. Transition/Coexistence Mechanism
SPs will typically use transition mechanisms such as 6rd, 6PE, MAP, SPs will typically use transition mechanisms, such as 6rd, 6PE, MAP,
and NAT64 which have been analyzed in the transition and coexistence and NAT64, which have been analyzed in the transition and coexistence
Section 2.7 section. (Section 2.7).
4.3. Lawful Intercept 4.3. Lawful Intercept
The Lawful Intercept requirements are similar for IPv6 and IPv4 The lawful intercept requirements are similar for IPv6 and IPv4
architectures and will be subject to the laws enforced in different architectures and will be subject to the laws enforced in different
geographic regions. The local issues with each jurisdiction can make geographic regions. The local issues with each jurisdiction can make
this challenging and both corporate legal and privacy personnel this challenging and both corporate legal and privacy personnel
should be involved in discussions pertaining to what information gets should be involved in discussions pertaining to what information gets
logged and with regard to the respective log retention policies for logged and with regard to the respective log retention policies for
this information. this information.
The target of interception will usually be a residential subscriber The target of interception will usually be a residential subscriber
(e.g., his/her PPP session, physical line, or CPE MAC address). In (e.g., his/her PPP session, physical line, or CPE MAC address). In
the absence of IPv6 NAT on the CPE, IPv6 has the possibility to allow the absence of IPv6 NAT on the CPE, IPv6 has the possibility to allow
for intercepting the traffic from a single host (i.e., a /128 target) for intercepting the traffic from a single host (i.e., a /128 target)
rather than the whole set of hosts of a subscriber (which could be a rather than the whole set of hosts of a subscriber (which could be a
/48, /60, or /64). /48, /60, or /64).
In contrast, in mobile environments, since the 3GPP specifications In contrast, in mobile environments, since the 3GPP specifications
allocate a /64 per device, it may be sufficient to intercept traffic allocate a /64 per device, it may be sufficient to intercept traffic
from the /64 rather than specific /128's (since each time the device from the /64 rather than specific /128s (since each time the device
establishes a data connection it gets a new IID). establishes a data connection, it gets a new IID).
5. Residential Users Security Considerations 5. Residential Users Security Considerations
The IETF Homenet working group is working on standards and guidelines The IETF Home Networking (homenet) Working Group is working on
for IPv6 residential networks; this obviously includes operational standards and guidelines for IPv6 residential networks; this
security considerations; but this is still work in progress. obviously includes operational security considerations, but this is
[RFC8520] is an interesting approach on how firewalls could retrieve still a work in progress. [RFC8520] is an interesting approach on
and apply specific security policies to some residential devices. how firewalls could retrieve and apply specific security policies to
some residential devices.
Some residential users have less experience and knowledge about Some residential users have less experience and knowledge about
security or networking than experimented operators. As most of the security or networking than experimented operators. As most of the
recent hosts (e.g., smartphones, tablets) have IPv6 enabled by recent hosts (e.g., smartphones and tablets) have IPv6 enabled by
default, IPv6 security is important for those users. Even with an default, IPv6 security is important for those users. Even with an
IPv4-only ISP, those users can get IPv6 Internet access with the help IPv4-only ISP, those users can get IPv6 Internet access with the help
of Teredo (Section 2.7.2.8) tunnels. Several peer-to-peer programs of Teredo (Section 2.7.2.8) tunnels. Several peer-to-peer programs
support IPv6 and those programs can initiate a Teredo tunnel through support IPv6, and those programs can initiate a Teredo tunnel through
an IPv4 residential gateway, with the consequence of making the an IPv4 residential gateway, with the consequence of making the
internal host reachable from any IPv6 host on the Internet. It is internal host reachable from any IPv6 host on the Internet.
therefore recommended that all host security products (including Therefore, it is recommended that all host security products
personal firewalls) are configured with a dual-stack security policy. (including personal firewalls) are configured with a dual-stack
security policy.
If the residential CPE has IPv6 connectivity, [RFC7084] defines the If the residential CPE has IPv6 connectivity, [RFC7084] defines the
requirements of an IPv6 CPE and does not take a position on the requirements of an IPv6 CPE and does not take a position on the
debate of default IPv6 security policy as defined in [RFC6092]: debate of default IPv6 security policy, as defined in [RFC6092]:
o outbound only: allowing all internally initiated connections and outbound only:
block all externally initiated ones, which is a common default Allowing all internally initiated connections and blocking all
security policy enforced by IPv4 Residential Gateway doing NAPT externally initiated ones, which is a common default security
but it also breaks the end-to-end reachability promise of IPv6. policy enforced by IPv4 residential gateway doing NAPT, but it
[RFC6092] lists several recommendations to design such a CPE; also breaks the end-to-end reachability promise of IPv6.
[RFC6092] lists several recommendations to design such a CPE.
o open/transparent: allowing all internally and externally initiated open/transparent:
connections, therefore restoring the end-to-end nature of the Allowing all internally and externally initiated connections,
Internet for IPv6 traffic but having a different security policy therefore, restoring the end-to-end nature of the Internet for
for IPv6 than for IPv4. IPv6 traffic but having a different security policy for IPv6 than
for IPv4.
[RFC6092] REC-49 states that a choice must be given to the user to REC-49 states that a choice must be given to the user to select one
select one of those two policies. of those two policies [RFC6092].
6. Further Reading 6. Further Reading
There are several documents that describe in more detail the security There are several documents that describe in more detail the security
of an IPv6 network; these documents are not written by the IETF and of an IPv6 network; these documents are not written by the IETF and
some of them are dated but are listed here for the reader's some of them are dated but are listed here for the reader's
convenience: convenience:
1. Guidelines for the Secure Deployment of IPv6 [NIST] * Guidelines for the Secure Deployment of IPv6 [NIST]
2. North American IPv6 Task Force Technology Report - IPv6 Security
Technology Paper [NAv6TF_Security]
3. IPv6 Security [IPv6_Security_Book]
7. Acknowledgements * North American IPv6 Task Force Technology Report - IPv6 Security
Technology Paper [NAv6TF_Security]
The authors would like to thank the following people for their useful * IPv6 Security [IPv6_Security_Book]
comments: Mikael Abrahamsson, Fred Baker, Mustafa Suha Botsali,
Mohamed Boucadair, Brian Carpenter, Tim Chown, Lorenzo Colitti, Roman
Danyliw (IESG review), Markus de Bruen, Lars Eggert (IESG review),
Tobias Fiebig, Fernando Gont, Jeffry Handal, Lee Howard, Benjamin
Kaduk (IESG review), Panos Kampanakis, Erik Kline, Jouni Korhonen,
Warren Kumari (IESG review), Ted Lemon, Mark Lentczner, Acee Lindem
(and his detailed nits), Jen Linkova (and her detailed review), Gyan
S. Mishra (the document shepherd), Jordi Palet, Alvaro Retana (IESG
review), Zaheduzzaman Sarker (IESG review), Bob Sleigh, Donald Smith,
Tarko Tikan, Ole Troan, Bernie Volz (by alphabetical order).
8. Security Considerations 7. Security Considerations
This memo attempts to give an overview of security considerations of This memo attempts to give an overview of security considerations of
operating an IPv6 network both for an IPv6-only network and for operating an IPv6 network both for an IPv6-only network and for
networks utilizing the most widely deployed IPv4/IPv6 coexistence networks utilizing the most widely deployed IPv4/IPv6 coexistence
strategies. strategies.
8. IANA Considerations
This document has no IANA actions.
9. References 9. References
9.1. Normative References 9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200, (IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017, DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>. <https://www.rfc-editor.org/info/rfc8200>.
9.2. Informative References 9.2. Informative References
[CYMRU] Team, C., "The Bogon Reference", Existing in 2021, [CYMRU] Team Cymru, "The Bogon Reference", <https://team-
<https://team-cymru.com/community-services/bogon- cymru.com/community-services/bogon-reference/>.
reference/>.
[ENTROPYIP] [ENTROPYIP]
Foremski, P., Plonka, D., and A. Berger, "Entropy/IP: Foremski, P., Plonka, D., and A. Berger, "Entropy/IP:
Uncovering Structure in IPv6 Addresses", Uncovering Structure in IPv6 Addresses", November 2016,
<http://www.entropy-ip.com/>. <http://www.entropy-ip.com/>.
[europol-cgn] [europol-cgn]
Europol, "ARE YOU SHARING THE SAME IP ADDRESS AS A Europol, "Are you sharing the same IP address as a
CRIMINAL? LAW ENFORCEMENT CALL FOR THE END OF CARRIER criminal? Law enforcement call for the end of Carrier
GRADE NAT (CGN) TO INCREASE ACCOUNTABILITY ONLINE", Grade Nat (CGN) to increase accountability online",
October 2017, October 2017,
<https://www.europol.europa.eu/newsroom/news/are-you- <https://www.europol.europa.eu/newsroom/news/are-you-
sharing-same-ip-address-criminal-law-enforcement-call-for- sharing-same-ip-address-criminal-law-enforcement-call-for-
end-of-carrier-grade-nat-cgn-to-increase-accountability- end-of-carrier-grade-nat-cgn-to-increase-accountability-
online>. online>.
[GDPR] Union, O. J. O. T. E., "Regulation (EU) 2016/679 of the [GDPR] European Union, "Regulation (EU) 2016/679 of the European
European Parliament and of the Council of 27 April 2016 on Parliament and of the Council of 27 April 2016 on the
the protection of natural persons with regard to the protection of natural persons with regard to the
processing of personal data and on the free movement of processing of personal data and on the free movement of
such data, and repealing Directive 95/46/EC (General Data such data, and repealing Directive 95/46/EC (General Data
Protection Regulation)", April 2016, Protection Regulation)", Official Journal of the European
Union, April 2016,
<https://eur-lex.europa.eu/eli/reg/2016/679/oj>. <https://eur-lex.europa.eu/eli/reg/2016/679/oj>.
[I-D.ietf-opsec-ipv6-eh-filtering]
Gont, F. and W. Liu, "Recommendations on the Filtering of
IPv6 Packets Containing IPv6 Extension Headers at Transit
Routers", draft-ietf-opsec-ipv6-eh-filtering-07 (work in
progress), January 2021.
[I-D.kampanakis-6man-ipv6-eh-parsing]
Kampanakis, P., "Implementation Guidelines for parsing
IPv6 Extension Headers", draft-kampanakis-6man-ipv6-eh-
parsing-01 (work in progress), August 2014.
[IANA-IPFIX] [IANA-IPFIX]
IANA, "IP Flow Information Export (IPFIX) Entities", IANA, "IP Flow Information Export (IPFIX) Entities",
<http://www.iana.org/assignments/ipfix>. <http://www.iana.org/assignments/ipfix>.
[IEEE-802.1X] [IEEE-802.1X]
IEEE, "IEEE Standard for Local and metropolitan area IEEE, "IEEE Standard for Local and Metropolitan Area
networks - Port-Based Network Access Control", IEEE Std Networks--Port-Based Network Access Control", IEEE Std
802.1X-2010, February 2010. 802.1X-2020, February 2020.
[IPV6-EH-FILTERING]
Gont, F. and W. Liu, "Recommendations on the Filtering of
IPv6 Packets Containing IPv6 Extension Headers at Transit
Routers", Work in Progress, Internet-Draft, draft-ietf-
opsec-ipv6-eh-filtering-08, 3 June 2021,
<https://datatracker.ietf.org/doc/html/draft-ietf-opsec-
ipv6-eh-filtering-08>.
[IPV6-EH-PARSING]
Kampanakis, P., "Implementation Guidelines for parsing
IPv6 Extension Headers", Work in Progress, Internet-Draft,
draft-kampanakis-6man-ipv6-eh-parsing-01, 5 August 2014,
<https://datatracker.ietf.org/doc/html/draft-kampanakis-
6man-ipv6-eh-parsing-01>.
[IPv6_Security_Book] [IPv6_Security_Book]
Hogg, S. and E. Vyncke, "IPv6 Security", Hogg, S. and É. Vyncke, "IPv6 Security", CiscoPress,
ISBN 1-58705-594-5, Publisher CiscoPress, December 2008. ISBN 1587055945, December 2008.
[KRISTOFF] [KRISTOFF] Kristoff, J., Ghasemisharif, M., Kanich, C., and J.
Kristoff, J., Ghasemisharif, M., Kanich, C., and J.
Polakis, "Plight at the End of the Tunnel: Legacy IPv6 Polakis, "Plight at the End of the Tunnel: Legacy IPv6
Transition Mechanisms in the Wild", March 2021, Transition Mechanisms in the Wild", March 2021,
<https://dataplane.org/jtk/publications/kgkp-pam-21.pdf>. <https://dataplane.org/jtk/publications/kgkp-pam-21.pdf>.
[NAv6TF_Security] [NAv6TF_Security]
Kaeo, M., Green, D., Bound, J., and Y. Pouffary, "North Kaeo, M., Green, D., Bound, J., and Y. Pouffary, "North
American IPv6 Task Force Technology Report - IPv6 Security American IPv6 Task Force (NAv6TF) Technology Report "IPv6
Technology Paper", 2006, Security Technology Paper", July 2006,
<http://www.ipv6forum.com/dl/white/ <http://www.ipv6forum.com/dl/white/
NAv6TF_Security_Report.pdf>. NAv6TF_Security_Report.pdf>.
[NIST] Frankel, S., Graveman, R., Pearce, J., and M. Rooks, [NIST] Frankel, S., Graveman, R., Pearce, J., and M. Rooks,
"Guidelines for the Secure Deployment of IPv6", 2010, "Guidelines for the Secure Deployment of IPv6", December
<http://csrc.nist.gov/publications/nistpubs/800-119/ 2010, <http://csrc.nist.gov/publications/nistpubs/800-119/
sp800-119.pdf>. sp800-119.pdf>.
[RADB] INC., M. N., "RADb The Internet Routing Registry", [RADB] Merit Network, Inc., "RADb: The Internet Routing
Existing in 2021, <https://www.radb.net/>. Registry", <https://www.radb.net/>.
[REY_PF] Rey, E., "Local Packet Filtering with IPv6", July 2017, [REY_PF] Rey, E., "Local Packet Filtering with IPv6", July 2017,
<https://labs.ripe.net/Members/enno_rey/local-packet- <https://labs.ripe.net/Members/enno_rey/local-packet-
filtering-with-ipv6>. filtering-with-ipv6>.
[RFC0826] Plummer, D., "An Ethernet Address Resolution Protocol: Or [RFC0826] Plummer, D., "An Ethernet Address Resolution Protocol: Or
Converting Network Protocol Addresses to 48.bit Ethernet Converting Network Protocol Addresses to 48.bit Ethernet
Address for Transmission on Ethernet Hardware", STD 37, Address for Transmission on Ethernet Hardware", STD 37,
RFC 826, DOI 10.17487/RFC0826, November 1982, RFC 826, DOI 10.17487/RFC0826, November 1982,
<https://www.rfc-editor.org/info/rfc826>. <https://www.rfc-editor.org/info/rfc826>.
[RFC1918] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G., [RFC1918] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G.
and E. Lear, "Address Allocation for Private Internets", J., and E. Lear, "Address Allocation for Private
BCP 5, RFC 1918, DOI 10.17487/RFC1918, February 1996, Internets", BCP 5, RFC 1918, DOI 10.17487/RFC1918,
<https://www.rfc-editor.org/info/rfc1918>. February 1996, <https://www.rfc-editor.org/info/rfc1918>.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol", [RFC2131] Droms, R., "Dynamic Host Configuration Protocol",
RFC 2131, DOI 10.17487/RFC2131, March 1997, RFC 2131, DOI 10.17487/RFC2131, March 1997,
<https://www.rfc-editor.org/info/rfc2131>. <https://www.rfc-editor.org/info/rfc2131>.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460, (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
December 1998, <https://www.rfc-editor.org/info/rfc2460>. December 1998, <https://www.rfc-editor.org/info/rfc2460>.
[RFC2529] Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4 [RFC2529] Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4
skipping to change at page 45, line 45 skipping to change at line 2161
[RFC3704] Baker, F. and P. Savola, "Ingress Filtering for Multihomed [RFC3704] Baker, F. and P. Savola, "Ingress Filtering for Multihomed
Networks", BCP 84, RFC 3704, DOI 10.17487/RFC3704, March Networks", BCP 84, RFC 3704, DOI 10.17487/RFC3704, March
2004, <https://www.rfc-editor.org/info/rfc3704>. 2004, <https://www.rfc-editor.org/info/rfc3704>.
[RFC3756] Nikander, P., Ed., Kempf, J., and E. Nordmark, "IPv6 [RFC3756] Nikander, P., Ed., Kempf, J., and E. Nordmark, "IPv6
Neighbor Discovery (ND) Trust Models and Threats", Neighbor Discovery (ND) Trust Models and Threats",
RFC 3756, DOI 10.17487/RFC3756, May 2004, RFC 3756, DOI 10.17487/RFC3756, May 2004,
<https://www.rfc-editor.org/info/rfc3756>. <https://www.rfc-editor.org/info/rfc3756>.
[RFC3924] Baker, F., Foster, B., and C. Sharp, "Cisco Architecture
for Lawful Intercept in IP Networks", RFC 3924,
DOI 10.17487/RFC3924, October 2004,
<https://www.rfc-editor.org/info/rfc3924>.
[RFC3964] Savola, P. and C. Patel, "Security Considerations for [RFC3964] Savola, P. and C. Patel, "Security Considerations for
6to4", RFC 3964, DOI 10.17487/RFC3964, December 2004, 6to4", RFC 3964, DOI 10.17487/RFC3964, December 2004,
<https://www.rfc-editor.org/info/rfc3964>. <https://www.rfc-editor.org/info/rfc3964>.
[RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander, [RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander,
"SEcure Neighbor Discovery (SEND)", RFC 3971, "SEcure Neighbor Discovery (SEND)", RFC 3971,
DOI 10.17487/RFC3971, March 2005, DOI 10.17487/RFC3971, March 2005,
<https://www.rfc-editor.org/info/rfc3971>. <https://www.rfc-editor.org/info/rfc3971>.
[RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)", [RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)",
skipping to change at page 53, line 5 skipping to change at line 2499
[RFC7039] Wu, J., Bi, J., Bagnulo, M., Baker, F., and C. Vogt, Ed., [RFC7039] Wu, J., Bi, J., Bagnulo, M., Baker, F., and C. Vogt, Ed.,
"Source Address Validation Improvement (SAVI) Framework", "Source Address Validation Improvement (SAVI) Framework",
RFC 7039, DOI 10.17487/RFC7039, October 2013, RFC 7039, DOI 10.17487/RFC7039, October 2013,
<https://www.rfc-editor.org/info/rfc7039>. <https://www.rfc-editor.org/info/rfc7039>.
[RFC7045] Carpenter, B. and S. Jiang, "Transmission and Processing [RFC7045] Carpenter, B. and S. Jiang, "Transmission and Processing
of IPv6 Extension Headers", RFC 7045, of IPv6 Extension Headers", RFC 7045,
DOI 10.17487/RFC7045, December 2013, DOI 10.17487/RFC7045, December 2013,
<https://www.rfc-editor.org/info/rfc7045>. <https://www.rfc-editor.org/info/rfc7045>.
[RFC7050] Savolainen, T., Korhonen, J., and D. Wing, "Discovery of
the IPv6 Prefix Used for IPv6 Address Synthesis",
RFC 7050, DOI 10.17487/RFC7050, November 2013,
<https://www.rfc-editor.org/info/rfc7050>.
[RFC7084] Singh, H., Beebee, W., Donley, C., and B. Stark, "Basic [RFC7084] Singh, H., Beebee, W., Donley, C., and B. Stark, "Basic
Requirements for IPv6 Customer Edge Routers", RFC 7084, Requirements for IPv6 Customer Edge Routers", RFC 7084,
DOI 10.17487/RFC7084, November 2013, DOI 10.17487/RFC7084, November 2013,
<https://www.rfc-editor.org/info/rfc7084>. <https://www.rfc-editor.org/info/rfc7084>.
[RFC7112] Gont, F., Manral, V., and R. Bonica, "Implications of [RFC7112] Gont, F., Manral, V., and R. Bonica, "Implications of
Oversized IPv6 Header Chains", RFC 7112, Oversized IPv6 Header Chains", RFC 7112,
DOI 10.17487/RFC7112, January 2014, DOI 10.17487/RFC7112, January 2014,
<https://www.rfc-editor.org/info/rfc7112>. <https://www.rfc-editor.org/info/rfc7112>.
skipping to change at page 57, line 25 skipping to change at line 2698
Shortest Path First (SPF) Trigger and Delay Strategies on Shortest Path First (SPF) Trigger and Delay Strategies on
IGP Micro-loops", RFC 8541, DOI 10.17487/RFC8541, March IGP Micro-loops", RFC 8541, DOI 10.17487/RFC8541, March
2019, <https://www.rfc-editor.org/info/rfc8541>. 2019, <https://www.rfc-editor.org/info/rfc8541>.
[RFC8981] Gont, F., Krishnan, S., Narten, T., and R. Draves, [RFC8981] Gont, F., Krishnan, S., Narten, T., and R. Draves,
"Temporary Address Extensions for Stateless Address "Temporary Address Extensions for Stateless Address
Autoconfiguration in IPv6", RFC 8981, Autoconfiguration in IPv6", RFC 8981,
DOI 10.17487/RFC8981, February 2021, DOI 10.17487/RFC8981, February 2021,
<https://www.rfc-editor.org/info/rfc8981>. <https://www.rfc-editor.org/info/rfc8981>.
[SCANNING] [SCANNING] Barnes, R., Altmann, R., and D. Kerr, "Mapping the Great
Barnes, R., Altmann, R., and D. Kerr, "Mapping the Great
Void - Smarter scanning for IPv6", February 2012, Void - Smarter scanning for IPv6", February 2012,
<http://www.caida.org/workshops/isma/1202/slides/ <http://www.caida.org/workshops/isma/1202/slides/
aims1202_rbarnes.pdf>. aims1202_rbarnes.pdf>.
[WEBER_VPN] [WEBER_VPN]
Weber, J., "Dynamic IPv6 Prefix - Problems and VPNs", Weber, J., "Dynamic IPv6 Prefix - Problems and VPNs",
March 2018, <https://blog.webernetz.net/wp- March 2018, <https://blog.webernetz.net/wp-
content/uploads/2018/03/TR18-Johannes-Weber-Dynamic-IPv6- content/uploads/2018/03/TR18-Johannes-Weber-Dynamic-IPv6-
Prefix-Problems-and-VPNs.pdf>. Prefix-Problems-and-VPNs.pdf>.
Acknowledgements
The authors would like to thank the following people for their useful
comments (in alphabetical order): Mikael Abrahamsson, Fred Baker,
Mustafa Suha Botsali, Mohamed Boucadair, Brian Carpenter, Tim Chown,
Lorenzo Colitti, Roman Danyliw (IESG Review), Markus de Bruen, Lars
Eggert (IESG review), Tobias Fiebig, Fernando Gont, Jeffry Handal,
Lee Howard, Benjamin Kaduk (IESG review), Panos Kampanakis, Erik
Kline, Jouni Korhonen, Warren Kumari (IESG review), Ted Lemon, Mark
Lentczner, Acee Lindem (and his detailed nits), Jen Linkova (and her
detailed review), Gyan S. Mishra (the Document Shepherd), Jordi
Palet, Alvaro Retana (IESG review), Zaheduzzaman Sarker (IESG
review), Bob Sleigh, Donald Smith, Tarko Tikan, Ole Troan, and Bernie
Volz.
Authors' Addresses Authors' Addresses
Eric Vyncke Éric Vyncke
Cisco Cisco
De Kleetlaan 6a De Kleetlaan 6a
Diegem 1831 1831 Diegem
Belgium Belgium
Phone: +32 2 778 4677 Phone: +32 2 778 4677
Email: evyncke@cisco.com Email: evyncke@cisco.com
Kiran Kumar
Square Kiran Kumar Chittimaneni
1455 Market Street, Suite 600
San Francisco 94103
United States of America
Email: kk.chittimaneni@gmail.com Email: kk.chittimaneni@gmail.com
Merike Kaeo Merike Kaeo
Double Shot Security Double Shot Security
3518 Fremont Ave N 363 3518 Fremont Ave N 363
Seattle 98103 Seattle, 98103
United States of America United States of America
Phone: +12066696394 Phone: +12066696394
Email: merike@doubleshotsecurity.com Email: merike@doubleshotsecurity.com
Enno Rey Enno Rey
ERNW ERNW
Carl-Bosch-Str. 4 Carl-Bosch-Str. 4
Heidelberg, Baden-Wuertemberg 69115 69115 Heidelberg Baden-Wuertemberg
Germany Germany
Phone: +49 6221 480390 Phone: +49 6221 480390
Email: erey@ernw.de Email: erey@ernw.de
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