IPv6 Security – Part 2

The second part of the 3-part series is where the rubber meets the road. The first part was an introduction to IPv6 for those without a foundation in IPv6. This article will look at the various security options that come with many of the new protocols that are part of the IPv6 protocol stack.

IPv6 had for a long time a reputation for being less secure than IPv4, and in all fairness, some of the decisions made in the beginning, back in the 90s, did weaken some of the features in a modern infrastructure environment. Those weaknesses have all been removed from the version of IPv6 that we are deploying currently. On top of that, even with the larger packet because of the 128-bit addresses spaces, IPv6 is faster than IPv4 because of routing efficiencies due to the new addresses.

Security features

IPv6 introduces several security features compared to its predecessor, IPv4. Some of the key security features of IPv6 include:

  • IPsec (Internet Protocol Security): IPsec is a set of protocols that provides confidentiality, integrity, and authenticity for IP packet traffic. It offers end-to-end security by encrypting and authenticating IPv6 packets. IPsec can be used to establish secure communication channels between devices, protecting against eavesdropping, tampering, and spoofing attacks.
  • Larger Address Space: IPv6 significantly expands the address space compared to IPv4, which helps mitigate certain types of attacks, such as IP address scanning and IP address exhaustion. The larger address space allows for better address management and allocation policies, reducing the likelihood of address conflicts and facilitating more secure network designs.
  • Stateless Address Autoconfiguration (SLAAC) Enhancements: SLAAC is a feature in IPv6 that allows hosts to automatically configure their addresses without relying on a DHCP server. In IPv6, SLAAC has been enhanced to include Secure Neighbor Discovery (SEND), which provides secure address configuration and neighbor discovery processes, protecting against address spoofing and impersonation attacks.
  • Mandatory Support for Extension Headers: IPv6 mandates support for extension headers, which provide additional functionality beyond the base IPv6 header. This allows for the inclusion of security-related extension headers, such as the Authentication Header (AH) and Encapsulating Security Payload (ESP), which are used for IPsec encryption and authentication.
  • Improved Routing Security: IPv6 includes features like Secure Neighbor Discovery (SEND) and Router Advertisement (RA) Guard that help protect against rogue router advertisements and neighbor discovery attacks. These mechanisms help ensure that hosts receive legitimate routing information and prevent attackers from redirecting traffic.
  • Simplified Network Address Translation (NAT): IPv6 eliminates the need for Network Address Translation (NAT) in most cases. NAT was commonly used in IPv4 networks as a security measure, but it introduced complexities and potential vulnerabilities. With IPv6, end-to-end connectivity is the default, reducing the reliance on NAT and improving network security.
  • Privacy Extensions for Addressing: IPv6 offers privacy extensions for temporary address generation, known as Temporary Address Privacy Extensions (TAP). These extensions help protect the privacy of devices by generating temporary addresses that change over time, making it more difficult to track and identify individual devices.

The next few sections will dig into more detail on each of the above points, including DHCPv6 and IGMPv6.


You might ask yourself why IPsec is part of IPv6. IPsec was added to IPv4 originally, but has been designed into IPv6 from the beginning, making it a core part of the IPv6 protocol stack. If you are already familiar with IPsec from IPv4, then feel free to skip to the next section!

Some of the key IPsec features in IPv6 are as follows:

  • Authentication Header (AH): AH is an IPsec protocol that provides authentication and integrity protection for IPv6 packets. It ensures that the contents of the packet are not modified during transmission and that the sender’s identity is verified. AH can protect the entire IPv6 packet, including the IPv6 header and upper-layer protocol data.
  • Encapsulating Security Payload (ESP): ESP is another IPsec protocol that provides confidentiality, authentication, and integrity protection for IPv6 packets. It encrypts the payload of the IPv6 packet to ensure that it remains confidential during transmission. ESP can operate in either transport mode, where only the payload is encrypted, or tunnel mode, where the entire IP packet is encapsulated and encrypted.
  • Security Associations (SAs): SAs are used in IPsec to establish and maintain the security parameters between communicating entities. SAs define the security services applied to the traffic, including the encryption algorithms, integrity algorithms, and keying material used for authentication. IPv6 incorporates the use of SAs for IPsec communication, ensuring that both ends of a communication channel agree on the security parameters.
  • Manual Keying or IKEv2: IPv6 supports both manual keying and Internet Key Exchange version 2 (IKEv2) for establishing and managing security associations. Manual keying involves manually configuring the security parameters on each end of the communication channel. On the other hand, IKEv2 is a key exchange protocol that allows for automated negotiation and management of security associations, providing a more flexible and scalable approach.
  • IPv6-in-IPv6 Tunneling: IPv6 provides support for IPsec over IPv6-in-IPv6 tunneling. This allows the establishment of secure communication channels between IPv6 hosts or networks across IPv6 tunnel connections. IPsec can be applied to the inner IPv6 packets, ensuring end-to-end security over the tunnel.
  • Mobility and IPsec: IPv6 incorporates IPsec functionality within the Mobile IPv6 protocol, allowing mobile nodes to establish secure communication while roaming between different IPv6 networks. IPsec protects the signaling and data traffic between the mobile node and its home agent or correspondent node, ensuring secure mobility management.


DHCPv6 (Dynamic Host Configuration Protocol for IPv6) includes several security features to ensure secure address assignment and configuration for IPv6 networks. Some of the key security features in DHCPv6 are:

  • Secure DHCPv6 (DHCPv6-Secure): DHCPv6-Secure is an extension to DHCPv6 that provides security enhancements. It includes mechanisms for authentication and integrity protection of DHCPv6 messages exchanged between clients and servers. Authentication can be achieved using techniques like IPsec or Transport Layer Security (TLS), ensuring that DHCPv6 messages are exchanged only with trusted entities.
  • Cryptographically Generated Addresses (CGA): DHCPv6 can support Cryptographically Generated Addresses (CGA), which are IPv6 addresses generated based on cryptographic techniques. CGA addresses can provide additional security by ensuring that only authorized devices with valid cryptographic credentials can acquire specific IPv6 addresses through DHCPv6.
  • Prefix Delegation (PD) Authorization: DHCPv6 supports Prefix Delegation (PD), which allows routers to delegate portions of the IPv6 address prefix to requesting routers. DHCPv6 servers can include authorization mechanisms to ensure that only authorized routers can receive prefix delegations, preventing unauthorized network reconfiguration or rogue routing.
  • IPv6 Prefix Stability: DHCPv6 offers mechanisms to ensure the stability and consistency of assigned IPv6 prefixes. This helps prevent address spoofing and unauthorized network renumbering. DHCPv6 servers can maintain a consistent mapping of prefixes to clients and enforce stability by providing fixed prefixes or verifying the validity of changes requested by clients.
  • Secure Neighbor Discovery (SEND): While SEND is not specific to DHCPv6, it complements DHCPv6 security by providing secure neighbor discovery mechanisms. SEND enhances IPv6 address assignment by ensuring the authenticity and integrity of Neighbor Discovery Protocol (NDP) messages, protecting against address spoofing and impersonation attacks.
  • DHCPv6 Server Access Control: Access control mechanisms can be implemented on DHCPv6 servers to restrict access and control the clients that can make requests. This helps prevent unauthorized clients from obtaining IPv6 addresses or configuration information from the DHCPv6 server.
  • DHCPv6 Relay Agent Guard: DHCPv6 relay agent guard is a security feature implemented on switches to protect against rogue DHCPv6 servers or relay agents. It verifies the authenticity and legitimacy of DHCPv6 server and relay agent messages, preventing malicious entities from intercepting or modifying DHCPv6 traffic.

The relay agent mentioned last, requires that the various network vendors have implemented this feature on the switches. All of the bigger networking vendors, Fortinet, Cisco, HPE, and Juniper have all done that, but it might not be the case if your network infrastructures is older or on smaller networking vendors.

It’s important to note that the effective implementation of DHCPv6 security features requires proper configuration, adherence to security best practices, and the use of compatible network infrastructure. Network administrators should consider these security features and deploy DHCPv6 in a secure manner to protect against potential vulnerabilities and threats.


IGMPv6 (Internet Group Management Protocol version 6) is a protocol used in IPv6 networks for managing multicast group memberships. While IGMPv6 itself does not provide extensive security features, there are certain considerations and security mechanisms that can be implemented to enhance the security of IGMPv6 deployments. These include:

  • Router Access Control Lists (ACLs): Router ACLs can be configured to control which hosts are allowed to send IGMPv6 messages. By filtering IGMPv6 messages based on source addresses or other criteria, unauthorized or malicious hosts can be prevented from joining or leaving multicast groups.
  • Querier Election: In IGMPv6, the Querier is responsible for sending Group Membership Queries and managing group memberships within a network segment. It’s important to ensure that Querier election mechanisms are secure, as an unauthorized device masquerading as a Querier could manipulate or disrupt multicast group memberships. Implementing authentication and access control for Querier election protocols can help prevent such attacks.
  • IGMPv6 Snooping: IGMPv6 snooping is a feature available in some network switches that listens to IGMPv6 messages and intelligently forwards multicast traffic only to the appropriate ports. IGMPv6 snooping prevents multicast traffic from being unnecessarily flooded to all ports, enhancing network efficiency and reducing the risk of eavesdropping or unauthorized access to multicast traffic.
  • Access Control: Implementing access control mechanisms at the network layer, such as firewalls or access control lists, can help control access to multicast groups. This ensures that only authorized hosts or network segments can join or receive multicast traffic.
  • Multicast Source Authentication: In scenarios where the authenticity of multicast sources is crucial, multicast source authentication mechanisms can be used. This involves verifying the authenticity and integrity of the multicast sources to prevent unauthorized or malicious sources from injecting false or malicious multicast traffic.

Like for the DHCPv6 above, many of the security features in IGMPv6 require that various other security features are already implemented in the IPv6 infrastructure to support the IGMPv6 security features.

IPv6 Extension Headers

IPv6 extension headers provide additional functionality beyond the base IPv6 header, allowing for more advanced features and options. While extension headers themselves do not have specific security features, their usage can impact the security of IPv6 communications. Here are some important considerations regarding the security implications of IPv6 extension headers:

  • Header Order and Processing: The order and processing of extension headers can affect security. Certain extension headers, such as the Authentication Header (AH) and Encapsulating Security Payload (ESP), provide security services like integrity, authentication, and encryption. It is important to ensure that security-related extension headers are processed early in the packet processing chain to prevent security-related issues or attacks.
  • Extension Header Inspection: Network devices, such as firewalls and intrusion detection/prevention systems, need to inspect and analyze extension headers to enforce security policies effectively. These devices should be capable of handling and parsing different extension headers correctly to identify potential security threats or anomalies.
  • Extension Header Fragmentation: Fragmentation of IPv6 packets containing extension headers can pose challenges for security devices and introduce potential security vulnerabilities. Reassembly and inspection of fragmented packets with extension headers may require additional processing and could potentially bypass security checks. Proper handling of fragmented packets containing extension headers is essential to maintain security.
  • Malicious or Unknown Extension Headers: IPv6 extension headers allow for flexibility, but they can also be misused or abused. Attackers may craft or inject malicious extension headers to bypass security mechanisms, exploit vulnerabilities, or disrupt network operations. It is crucial to validate and filter extension headers to ensure that only known, trusted, and necessary extension headers are allowed.
  • Routing Considerations: Some IPv6 extension headers, such as Routing Header (RH), can be leveraged to manipulate routing paths. Unauthorized or incorrect modification of routing information through extension headers can lead to traffic diversion, man-in-the-middle attacks, or network disruptions. Careful configuration and access control are required to prevent misuse of routing-related extension headers.
  • IPv6 Transition Mechanisms: During the transition from IPv4 to IPv6, certain mechanisms like IPv6-over-IPv4 tunneling (e.g., 6to4, Teredo) or IPv6-in-IPv4 encapsulation (e.g., GRE, IP-in-IP) may introduce additional extension headers. It is important to consider the security implications of these transition mechanisms and ensure that security policies are extended to the encapsulated IPv6 packets as well.

Overall, proper configuration, validation, inspection, and filtering of IPv6 extension headers are crucial for maintaining the security of IPv6 networks. Network administrators should stay updated with the latest security guidelines, best practices, and vendor recommendations to effectively secure IPv6 extension headers in their deployments.


There are many, many more features within IPv6 that can affect the security of an IPv6 network. Make sure that your foundation of IPv6 knowledge is up to speed before starting a serious IPv6 rollout in your own infrastructures.

The next and last article in this series will investigate how we can microsegment, while using IPv6. This is an area that has not received much attention, in my opinion, so I will give you some pointers on how to do it with IPv6.

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Tom Madsen
Senior Security Consulting Manager at Accenture | + posts

Tom Madsen has been active in the cybersecurity industry for more than 20 years. Tom graduated from the University of Aalborg and covered several technical roles in security during his professional career. He is certified as CISSP, CISA, CISM, CGEIT, CRISK, CCSP, CDSPE and CSSLP, and has published the book "The Art of War for Cybersecurity". He is currently writing a book 'Security Architecture - How & Why'.

Tom Madsen

Tom Madsen has been active in the cybersecurity industry for more than 20 years. Tom graduated from the University of Aalborg and covered several technical roles in security during his professional career. He is certified as CISSP, CISA, CISM, CGEIT, CRISK, CCSP, CDSPE and CSSLP, and has published the book "The Art of War for Cybersecurity". He is currently writing a book 'Security Architecture - How & Why'.

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