Question 592 of 2,152

IPv6 First Hop Security →hardMultiple ChoiceObjective-mapped

Quick Answer

The answer is that the RA Guard policy is misconfigured with device-role host on the router port Gi1/0/1. RA Guard is a First Hop Security feature that validates Router Advertisement messages; when a port is set to device-role host, the switch treats any device on that port as an end host and drops all incoming RAs, even from the legitimate router. This explains why the router sends RAs but hosts never receive them—the switch is actively blocking the advertisements at the port level. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding of IPv6 RA Guard policy application and the critical distinction between device-role router and device-role host. A common trap is assuming RA Guard only blocks rogue devices, but misassigning the role on the trusted router port will also drop legitimate RAs. Remember the memory tip: “Host drops, Router allows”—if you want RAs to pass, the port facing the router must be configured with device-role router.

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.

An engineer is troubleshooting an IPv6 connectivity issue where hosts on VLAN 10 cannot reach the internet. The switch is configured with IPv6 First Hop Security features including RA Guard and DHCPv6 Guard. The legitimate router is connected to port Gi1/0/1. The engineer notices that the router is sending RAs, but hosts are not receiving them. The switch shows that RA Guard is dropping packets on port Gi1/0/1. What is the most likely misconfiguration?

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.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.

Question 1hardmultiple choice

Open the full VLAN trunking answer →

A
The RA Guard policy is configured with 'device-role host' on port Gi1/0/1, which causes the switch to drop all RAs received on that port.
Correct because 'device-role host' tells the switch that only hosts are allowed on that port; RAs from a router will be dropped.
B
DHCPv6 Guard is configured on port Gi1/0/1, blocking the router's DHCPv6 server messages.
Why wrong: Incorrect because DHCPv6 Guard blocks DHCPv6 server messages, not RAs; the symptom is about RAs being dropped.
C
IPv6 Source Guard is enabled on the VLAN, and the router's IPv6 address is not in the binding table.
Why wrong: Incorrect because IPv6 Source Guard filters traffic based on source address, not RAs; RAs are multicast and typically not filtered by Source Guard.
D
The switch has IPv6 unicast-routing enabled, and it is sending its own RAs, causing a conflict.
Why wrong: Incorrect because the issue is that the router's RAs are being dropped, not that there are conflicting RAs.

Full breakdown with real-world context →

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

✓

The RA Guard policy is configured with 'device-role host' on port Gi1/0/1, which causes the switch to drop all RAs received on that port.

RA Guard drops RAs from devices that are not authorized as routers. If the legitimate router's MAC address is not included in the RA Guard policy's allowed list, or if the port is not configured with the correct device-role, the RAs will be dropped.

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.

✓
The RA Guard policy is configured with 'device-role host' on port Gi1/0/1, which causes the switch to drop all RAs received on that port.
Why this is correct
Correct because 'device-role host' tells the switch that only hosts are allowed on that port; RAs from a router will be dropped.
Clue confirmation
The clue words "first", "most likely" in the question point toward this answer.
Related concept
Access ports place end devices into a single VLAN.
✗
DHCPv6 Guard is configured on port Gi1/0/1, blocking the router's DHCPv6 server messages.
Why it's wrong here
Incorrect because DHCPv6 Guard blocks DHCPv6 server messages, not RAs; the symptom is about RAs being dropped.
✗
IPv6 Source Guard is enabled on the VLAN, and the router's IPv6 address is not in the binding table.
Why it's wrong here
Incorrect because IPv6 Source Guard filters traffic based on source address, not RAs; RAs are multicast and typically not filtered by Source Guard.
✗
The switch has IPv6 unicast-routing enabled, and it is sending its own RAs, causing a conflict.
Why it's wrong here
Incorrect because the issue is that the router's RAs are being dropped, not that there are conflicting RAs.

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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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: The RA Guard policy is configured with 'device-role host' on port Gi1/0/1, which causes the switch to drop all RAs received on that port. — RA Guard drops RAs from devices that are not authorized as routers. If the legitimate router's MAC address is not included in the RA Guard policy's allowed list, or if the port is not configured with the correct device-role, the RAs will be dropped.

What should I do if I get this 300-410 question wrong?

Are there clue words in this question I should notice?

Yes — watch for: "first", "most likely". 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.

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