mediumMultiple Choice
300-410 Practice Question: In IPv6 First Hop Security, which feature is used…
In IPv6 First Hop Security, which feature is used to prevent duplicate address detection (DAD) attacks by snooping Neighbor Discovery (ND) messages?
⚠ Common exam trap
It's easy for candidates to confuse ND Snooping with RA Guard or DHCPv6 Guard, thinking any 'Guard' feature handles DAD attacks, but only ND Snooping directly inspects Neighbor Discovery messages used in the DAD process.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
ND Snooping
C is correct because ND Snooping (Neighbor Discovery Snooping) is the IPv6 First Hop Security feature that prevents duplicate address detection (DAD) attacks by inspecting Neighbor Solicitation (NS) and Neighbor Advertisement (NA) messages. It builds a binding table of valid IPv6-to-MAC address mappings and drops any NS messages that attempt to claim an address already in use by another device, thereby blocking DAD-based spoofing attacks.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
RA Guard
Why it's wrong here
RA Guard filters ICMPv6 Router Advertisement and Redirect messages on untrusted ports, blocking rogue routers; it does not snoop Neighbor Solicitation or Advertisement used by DAD. It is tempting because both are IPv6 First Hop Security features operating on ICMPv6.
- ✗
DHCPv6 Guard
Why it's wrong here
DHCPv6 Guard filters DHCPv6 server and relay messages on untrusted ports; it does not inspect Neighbor Discovery traffic, so DAD attacks pass through. It is tempting because both are First Hop Security features, but DHCPv6 Guard operates on UDP 546/547, not ICMPv6 ND.
- ✓
ND Snooping
Why this is correct
ND Snooping inspects Neighbor Discovery messages and builds a binding table of IPv6 address-to-MAC mappings, letting the switch drop spoofed Neighbor Solicitation and Advertisement packets. This directly satisfies the stem's constraint: blocking duplicate address detection attacks by snooping ND traffic at the access layer.
- ✗
Source Guard
Why it's wrong here
Source Guard builds a binding table from DHCPv6 snooping and drops traffic whose IPv6 source does not match the binding; it does not inspect ND messages for DAD. It is tempting because it also mitigates spoofing, but its enforcement is source-address based, not ND-based.
Quick reference
Access Control Model Comparison
| Model | Acronym | Who Controls Access? | Best For |
|---|---|---|---|
| Discretionary Access Control | DAC | Resource owner | Small teams, file shares |
| Mandatory Access Control | MAC | System / security labels | Classified govt / military |
| Role-Based Access Control | RBAC | Administrator (via roles) | Enterprise environments |
| Attribute-Based Access Control | ABAC | Policy engine (user + resource attributes) | Fine-grained, dynamic policies |
| Rule-Based Access Control | RuBAC | System rules / ACLs | Firewall rules, network ACLs |
Go deeper
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 300-410 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 300-410 exam.