- A
IPv6 hosts on a segment are unable to obtain a global unicast address via SLAAC, even though a legitimate router is present.
This could be due to RA Guard blocking the router's Router Advertisements, preventing SLAAC.
- B
A newly connected switch causes existing hosts to lose IPv6 connectivity to the default gateway.
This may indicate ND Inspection or IPv6 Source Guard dropping valid ND packets from the new switch, or a binding table issue.
- C
Hosts on a VLAN receive Router Advertisements but do not update their default gateway.
RA Guard can be configured to drop RAs from unauthorized sources, or the policy may incorrectly mark the legitimate router as a host, causing hosts to ignore the RAs.
- D
IPv6 pings between two hosts on the same VLAN succeed, but pings to the router fail.
Why wrong: This could be a routing or gateway issue, but not necessarily an FHS problem; FHS typically blocks at Layer 2, not Layer 3 forwarding.
- E
The switch logs show frequent 'IPv6 address collision' messages.
Why wrong: Address collisions are typically detected by DAD (Duplicate Address Detection) and are not directly caused by FHS misconfiguration; they indicate a different issue.
Quick Answer
The answer is that the three symptoms indicating IPv6 First Hop Security misconfiguration are hosts failing to obtain IPv6 addresses via DHCPv6, sudden connectivity loss after a new switch is introduced, and hosts receiving Router Advertisements but not updating their default gateway. These symptoms point directly to specific FHS features being blocked or misapplied: DHCPv6 Guard prevents legitimate DHCP servers from assigning addresses, ND Inspection or Source Guard can drop traffic from an unknown switch port, and RA Guard misconfiguration can cause hosts to ignore valid RAs, leaving their gateway unchanged. On the Cisco CCNP ENARSI 300-410 exam, this question tests your ability to map real-world behavior to FHS mechanisms like RA Guard, ND Inspection, and DHCPv6 Guard, often with distractors that describe normal IPv6 operations or unrelated issues like duplicate address detection. A common trap is confusing a host’s failure to update its gateway with a simple routing problem, when the root cause is RA Guard filtering. Remember the mnemonic “DNR” for the three symptoms: DHCP failure, New switch disruption, and Router Advertisement ignored.
300-410 IPv6 First Hop Security Practice Question
This 300-410 practice question tests your understanding of ipv6 first hop security. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Which THREE symptoms indicate that IPv6 First Hop Security features are misconfigured or not functioning correctly? (Choose THREE.)
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"first"Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
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
IPv6 hosts on a segment are unable to obtain a global unicast address via SLAAC, even though a legitimate router is present.
These three symptoms are direct indicators of FHS issues: devices failing to obtain addresses suggests DHCPv6 Guard blocking, connectivity loss after a new switch suggests ND Inspection or Source Guard issues, and RA Guard misconfiguration can cause hosts to ignore RAs. The other options are not specific to FHS or are normal behavior.
Key principle: A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
IPv6 hosts on a segment are unable to obtain a global unicast address via SLAAC, even though a legitimate router is present.
- ✓
A newly connected switch causes existing hosts to lose IPv6 connectivity to the default gateway.
Why this is correct
This may indicate ND Inspection or IPv6 Source Guard dropping valid ND packets from the new switch, or a binding table issue.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Access ports place end devices into a single VLAN.
- ✓
Hosts on a VLAN receive Router Advertisements but do not update their default gateway.
Why this is correct
RA Guard can be configured to drop RAs from unauthorized sources, or the policy may incorrectly mark the legitimate router as a host, causing hosts to ignore the RAs.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Access ports place end devices into a single VLAN.
- ✗
IPv6 pings between two hosts on the same VLAN succeed, but pings to the router fail.
Why it's wrong here
This could be a routing or gateway issue, but not necessarily an FHS problem; FHS typically blocks at Layer 2, not Layer 3 forwarding.
- ✗
The switch logs show frequent 'IPv6 address collision' messages.
Why it's wrong here
Address collisions are typically detected by DAD (Duplicate Address Detection) and are not directly caused by FHS misconfiguration; they indicate a different issue.
Common exam traps
Common exam trap: an active trunk can still block the VLAN you need
A trunk being up does not prove every VLAN is crossing it. Check allowed VLAN lists, native VLAN mismatch, VLAN existence and access-port assignment.
Detailed technical explanation
How to think about this question
VLAN questions usually combine access-port and trunking clues. The key is to identify whether the issue is local to one switchport, caused by the trunk, or caused by the VLAN not existing where it needs to exist.
KKey Concepts to Remember
- Access ports place end devices into a single VLAN.
- Trunk ports carry multiple VLANs between switches.
- Allowed VLAN lists decide which VLANs can cross a trunk.
- Native VLAN mismatch can create confusing symptoms.
TExam Day Tips
- Use show vlan brief to verify access VLANs.
- Use show interfaces trunk to verify trunk state and allowed VLANs.
- Do not treat every same-VLAN issue as a routing problem.
Key takeaway
A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
Real-world example
How this comes up in practice
A help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
What to study next
Got this wrong? Here's your next step.
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 300-410 questions on switching, trunking, and access-port configuration.
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IPv6 First Hop Security — study guide chapter
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FAQ
Questions learners often ask
What does this 300-410 question test?
IPv6 First Hop Security — This question tests IPv6 First Hop Security — Access ports place end devices into a single VLAN..
What is the correct answer to this question?
The correct answer is: IPv6 hosts on a segment are unable to obtain a global unicast address via SLAAC, even though a legitimate router is present. — These three symptoms are direct indicators of FHS issues: devices failing to obtain addresses suggests DHCPv6 Guard blocking, connectivity loss after a new switch suggests ND Inspection or Source Guard issues, and RA Guard misconfiguration can cause hosts to ignore RAs. The other options are not specific to FHS or are normal behavior.
What should I do if I get this 300-410 question wrong?
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 300-410 questions on switching, trunking, and access-port configuration.
Are there clue words in this question I should notice?
Yes — watch for: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
What is the key concept behind this question?
Access ports place end devices into a single VLAN.
About these practice questions
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Last reviewed: Jun 18, 2026
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.
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