- A
Configure RA Guard with a policy that sets the legitimate router's port as 'device-role router' and all other ports as 'device-role host', and apply the policy globally.
Correct because RA Guard will allow RAs only on ports configured as 'device-role router', blocking rogue RAs on host ports.
- B
Enable DHCPv6 Guard on all ports to block any DHCPv6 server messages, which will also block RAs.
Why wrong: Incorrect because DHCPv6 Guard does not block RAs; it only blocks DHCPv6 server messages.
- C
Use IPv6 Source Guard to filter traffic from the rogue router based on its IPv6 address.
Why wrong: Incorrect because IPv6 Source Guard filters data traffic, not control plane messages like RAs; RA Guard is the appropriate feature.
- D
Configure a static IPv6 neighbor entry for the legitimate router on the switch to override rogue RAs.
Why wrong: Incorrect because static neighbor entries do not prevent the switch from processing rogue RAs; RA Guard is needed to drop them.
Quick Answer
The correct configuration approach is to configure RA Guard with a policy that sets the legitimate router’s port as device-role router and all other ports as device-role host, then apply the policy globally. This works because RA Guard is an IPv6 First Hop Security feature that inspects incoming Router Advertisements and drops any RA received on a port not explicitly trusted as a router port, thereby preventing rogue router advertisement prevention while allowing the authorized router to send legitimate RAs. On the Cisco CCNP ENARSI 300-410 exam, this topic tests your understanding of IPv6 RA Guard configuration under the First Hop Security domain, often appearing in scenario-based questions where a malicious RA attack must be mitigated without disrupting legitimate traffic. A common trap is applying the policy per-interface instead of globally, or forgetting to set the device-role on the trusted port. Memory tip: think “trust the port, guard the rest”—only the port with device-role router is allowed to send RAs.
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 issue where a rogue IPv6 router is sending false Router Advertisements on the network, causing hosts to use a malicious default gateway. The switch is configured with IPv6 First Hop Security features. The engineer wants to prevent this attack while allowing the legitimate router to send RAs. What is the correct configuration approach?
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
Configure RA Guard with a policy that sets the legitimate router's port as 'device-role router' and all other ports as 'device-role host', and apply the policy globally.
RA Guard is designed to prevent rogue RAs by allowing only authorized routers to send RAs. The correct approach is to configure RA Guard with a policy that trusts the legitimate router's port and drops RAs from all other ports.
Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Configure RA Guard with a policy that sets the legitimate router's port as 'device-role router' and all other ports as 'device-role host', and apply the policy globally.
Why this is correct
Correct because RA Guard will allow RAs only on ports configured as 'device-role router', blocking rogue RAs on host ports.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
OSPF neighbours must agree on key parameters.
- ✗
Enable DHCPv6 Guard on all ports to block any DHCPv6 server messages, which will also block RAs.
Why it's wrong here
Incorrect because DHCPv6 Guard does not block RAs; it only blocks DHCPv6 server messages.
- ✗
Use IPv6 Source Guard to filter traffic from the rogue router based on its IPv6 address.
Why it's wrong here
Incorrect because IPv6 Source Guard filters data traffic, not control plane messages like RAs; RA Guard is the appropriate feature.
- ✗
Configure a static IPv6 neighbor entry for the legitimate router on the switch to override rogue RAs.
Why it's wrong here
Incorrect because static neighbor entries do not prevent the switch from processing rogue RAs; RA Guard is needed to drop them.
Common exam traps
Common exam trap: OSPF can fail even when IP connectivity looks correct
OSPF neighbour formation depends on matching areas, timers, network type, authentication and passive-interface behaviour. Do not choose an answer only because the devices can ping.
Detailed technical explanation
How to think about this question
OSPF questions usually test the details that control adjacency and route selection. Read the neighbour state, area, router ID and interface configuration before deciding what is wrong.
KKey Concepts to Remember
- OSPF neighbours must agree on key parameters.
- Router ID selection can affect neighbour relationships and LSDB output.
- OSPF cost influences the preferred path.
- A route can appear in OSPF information but not become the installed route.
TExam Day Tips
- Check area mismatch first when OSPF adjacency fails.
- Review passive interfaces when a network is advertised but no neighbour forms.
- Use show ip ospf neighbor and show ip route clues carefully.
Key takeaway
OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Real-world example
How this comes up in practice
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
What to study next
Got this wrong? Here's your next step.
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.
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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 — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: Configure RA Guard with a policy that sets the legitimate router's port as 'device-role router' and all other ports as 'device-role host', and apply the policy globally. — RA Guard is designed to prevent rogue RAs by allowing only authorized routers to send RAs. The correct approach is to configure RA Guard with a policy that trusts the legitimate router's port and drops RAs from all other ports.
What should I do if I get this 300-410 question wrong?
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.
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?
OSPF neighbours must agree on key parameters.
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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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