IPv6 First Hop Security for Registered Locations

300-410 By islever Editorial Last updated Oct 18, 2026

Describe IPv6 First Hop security features (RA guard, DHCP guard, binding table, ND inspection/snooping, source guard)

Short answer

D Implement IPv6 Prefix Guard (DHCPv6 Guard) to validate that devices connect from assigned locations using registered IP addresses via the binding table.

Question

The network administrator must implement IPv6 in the network to allow only devices that not only have registered IP addresses but are also connecting from assigned locations. Which security feature must be implemented?

IPv6 Snooping
IPv6 Destination Guard
IPv6 Router Advertisement Guard
IPv6 Prefix Guard Correct Answer

Key Takeaways

The question requires a feature that validates both the IP address and the physical location (port/VLAN) of the connecting device, pointing towards a mechanism that checks against a dynamic binding table.

This question tests the selection of IPv6 First Hop Security features required to enforce that devices connect from assigned locations with registered IP addresses. The correct implementation is DHCPv6 Guard (often referred to as IPv6 Prefix Guard in this specific exam context) which utilizes the binding table.

Common mistake: Many learners choose IPv6 Destination Guard because it also uses a binding table but filters based on MAC addresses rather than verifying the registration process via DHCP/SLAAC interactions in the same way. Others mistakenly select Router Advertisement Guard, which only prevents rogue advertisements and does not verify client identity or location.

Expert Analysis

Why the Answer Is Correct

The requirement to allow devices that have 'registered IP addresses' and are 'connecting from assigned locations' describes the function of DHCPv6 Guard (listed here as IPv6 Prefix Guard). This feature operates by monitoring DHCPv6 messages and maintaining a database of bindings between IPv6 addresses, MAC addresses, and VLAN/interface information. When a packet arrives, the switch verifies if the source address matches an entry in this binding table, ensuring the device is using a legitimately assigned address at that specific port.

Why the Other Options Are Wrong

IPv6 Destination Guard filters traffic based on the destination IP and MAC address, primarily preventing IP spoofing, but it does not inherently manage the 'registration' aspect of the IP address assignment process itself. IPv6 Router Advertisement Guard protects against rogue RAs but does not validate individual client connections or their assigned IPs. IPv6 Snooping is a broader term often associated with Neighbor Discovery Inspection, which builds the binding table but is the underlying mechanism rather than the enforcement policy described.

Community Comment Notes

Community consensus is divided. User Zizu007 confirms option D, citing Cisco documentation regarding IPv6 Security. However, users like XxnightwingxX argue for B, noting that Destination Guard uses the binding table too. Another user points out that IPv6 Snooping bundles these features. Despite the confusion, the specific phrasing 'registered IP' strongly implies the use of the binding table created by guard mechanisms like DHCPv6 Guard (Prefix Guard).

Official Reference

https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipv6_fhsec/configuration/xe-16-10/ip6f-xe-16-10-book/ip6-snooping.pdf

This link opens the official vendor documentation in a new tab.

Exam Strategy

When you see keywords like 'registered', 'binding table', and 'assigned locations' in IPv6 security questions, prioritize DHCPv6 Guard or its equivalent name (Prefix Guard) over simple filtering mechanisms like RA Guard or Destination Guard.

Frequently Asked Questions

Why is IPv6 Prefix Guard preferred over Destination Guard?

Prefix Guard (DHCPv6 Guard) specifically manages the registration of IPs via DHCP/SLAAC and binds them to ports, whereas Destination Guard focuses on filtering based on existing bindings without managing the registration.

Does IPv6 Snooping provide the same security?

No, IPv6 Snooping (ND Inspection) helps build the binding table but does not actively drop packets from unregistered sources at the edge in the same enforcement manner as the Guard features.

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Discussion 5 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 5

Zizu007 👍 4 Answered D

Correct! https://www.cisco.com/c/en/us/td/docs/routers/7600/ios/15S/configuration/guide/7600_15_0s_book/IPv6_Security.html#62638
XxnightwingxX 👍 2 Answered B

I believe the answer is B. Prefix Guard doesn't use the binding table and Destination Guard does which aligns best with the "registered IP" requirement. Prefix Guard is more concerned with unauthorized prefix advertisements.
1chung 👍 2 Answered A

Correct answer is A
Luongchacha1 👍 1 Answered A

i go with A. https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipv6_fhsec/configuration/xe-16-10/ip6f-xe-16-10-book/ip6-snooping.pdf The IPv6 Snooping feature bundles several Layer 2 IPv6 first-hop security features, including IPv6 neighbor discovery inspection, IPv6 device tracking, IPv6 address glean, and IPv6 binding table recovery, to provide security and scalability. IPv6 ND inspection operates at Layer 2, or between Layer 2 and Layer 3, to provide IPv6 functions with security and scalability.
deech 👍 1 Answered B

B is correct

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