Question 617 of 2,152

IPv6 First Hop Security →mediumMultiple ChoiceObjective-mapped

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.

A network engineer runs the following command to troubleshoot an IPv6 First Hop Security issue:

R1# debug ipv6 nd raguard

*Mar  1 00:01:23.456: IPv6-ND-RA-Guard: R1, Fa0/0, RA received on port Fa0/0, src fe80::1, dst ff02::1
*Mar  1 00:01:23.456: IPv6-ND-RA-Guard: R1, Fa0/0, RA from fe80::1 is allowed by policy TRUSTED
*Mar  1 00:01:24.789: IPv6-ND-RA-Guard: R1, Fa0/0, RA received on port Fa0/0, src fe80::2, dst ff02::1
*Mar  1 00:01:24.789: IPv6-ND-RA-Guard: R1, Fa0/0, RA from fe80::2 is blocked by policy UNTRUSTED

What does this output indicate?

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.

A
RA Guard is configured with a policy that trusts fe80::1 and blocks fe80::2, preventing rogue RA attacks.
The debug confirms that fe80::1 is allowed by policy TRUSTED and fe80::2 is blocked by policy UNTRUSTED, which is the expected behavior for RA Guard.
B
RA Guard is blocking all RAs regardless of source, indicating a misconfiguration.
Why wrong: The output shows one RA allowed and one blocked, so not all RAs are blocked.
C
RA Guard is allowing all RAs but logging them for analysis.
Why wrong: The output explicitly shows a blocked RA, so not all are allowed.
D
RA Guard is not configured; the debug output is from default IPv6 ND behavior.
Why wrong: The debug output specifically references RA Guard policies, indicating it is configured.

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

✓

RA Guard is configured with a policy that trusts fe80::1 and blocks fe80::2, preventing rogue RA attacks.

The debug output shows that RA Guard is actively filtering Router Advertisement (RA) messages on interface Fa0/0. The first RA from fe80::1 is explicitly allowed by a policy named TRUSTED, while the second RA from fe80::2 is blocked by a policy named UNTRUSTED. This confirms that RA Guard is correctly configured to permit only authorized routers (fe80::1) and block potential rogue RA sources (fe80::2), preventing RA-based attacks in an IPv6 First Hop Security deployment.

Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.

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 is configured with a policy that trusts fe80::1 and blocks fe80::2, preventing rogue RA attacks.
Why this is correct
The debug confirms that fe80::1 is allowed by policy TRUSTED and fe80::2 is blocked by policy UNTRUSTED, which is the expected behavior for RA Guard.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
RA Guard is blocking all RAs regardless of source, indicating a misconfiguration.
Why it's wrong here
The output shows one RA allowed and one blocked, so not all RAs are blocked.
✗
RA Guard is allowing all RAs but logging them for analysis.
Why it's wrong here
The output explicitly shows a blocked RA, so not all are allowed.
✗
RA Guard is not configured; the debug output is from default IPv6 ND behavior.
Why it's wrong here
The debug output specifically references RA Guard policies, indicating it is configured.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Cisco often tests the misconception that RA Guard blocks all RAs or only logs them, when in fact it uses policy-based filtering that can selectively permit or deny based on the source link-local address and the configured device role.

Trap categories for this question

Command / output trap
The output shows one RA allowed and one blocked, so not all RAs are blocked.

Detailed technical explanation

How to think about this question

RA Guard, defined in RFC 6105 and implemented via the 'ipv6 nd raguard' command, uses port ACLs and device-tracking to classify hosts as routers or hosts. The policy names (TRUSTED/UNTRUSTED) are configured under 'ipv6 nd raguard policy' and can be applied per switchport; the switch then validates the source link-local address against the policy's 'device-role' setting. In a real-world scenario, an attacker on an untrusted port sending RAs with a spoofed source would be blocked, while a legitimate router on a trusted port is allowed, preventing man-in-the-middle attacks via rogue default gateways.

KKey Concepts to Remember

Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.

TExam Day Tips

Watch for words such as best, first, most likely and least administrative effort.
Review why wrong options are wrong, not only why the correct option is correct.

Key takeaway

Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.

Real-world example

How this comes up in practice

A security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.

What to study next

Got this wrong? Here's your next step.

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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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 — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: RA Guard is configured with a policy that trusts fe80::1 and blocks fe80::2, preventing rogue RA attacks. — The debug output shows that RA Guard is actively filtering Router Advertisement (RA) messages on interface Fa0/0. The first RA from fe80::1 is explicitly allowed by a policy named TRUSTED, while the second RA from fe80::2 is blocked by a policy named UNTRUSTED. This confirms that RA Guard is correctly configured to permit only authorized routers (fe80::1) and block potential rogue RA sources (fe80::2), preventing RA-based attacks in an IPv6 First Hop Security deployment.

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

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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?

Read the scenario before looking for a memorised answer.

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