Question 787 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 is troubleshooting an issue where IPv6 hosts are receiving multiple Router Advertisements from different routers, causing routing instability. The switch is configured with IPv6 First Hop Security features. The engineer wants to ensure that only the primary router's RAs are accepted by hosts. What is the most effective solution?

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: "primary"
Why it matters: Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.

Question 1mediummultiple choice

Study the full IPv6 explanation →

A
Configure RA Guard with a policy that includes the primary router's MAC address in the allowed list and apply it to all ports.
Correct because RA Guard will drop RAs from any router not in the allowed list, preventing multiple routers from sending RAs.
B
Enable DHCPv6 Guard to block DHCPv6 messages from the secondary router.
Why wrong: Incorrect because DHCPv6 Guard does not affect RAs; it only blocks DHCPv6 server messages.
C
Use IPv6 Source Guard to filter traffic from the secondary router.
Why wrong: Incorrect because IPv6 Source Guard filters data traffic, not RAs.
D
Configure the switch to act as a router and send its own RAs with a higher priority to override the secondary router.
Why wrong: Incorrect because this would add another router sending RAs, potentially worsening the instability; RA Guard is the correct tool.

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

✓

Configure RA Guard with a policy that includes the primary router's MAC address in the allowed list and apply it to all ports.

RA Guard can be used to allow only authorized routers to send RAs. By configuring an RA Guard policy that permits only the primary router's MAC address, RAs from other routers will be dropped, ensuring stability.

Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.

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 includes the primary router's MAC address in the allowed list and apply it to all ports.
Why this is correct
Correct because RA Guard will drop RAs from any router not in the allowed list, preventing multiple routers from sending RAs.
Clue confirmation
The clue words "first", "primary" in the question point toward this answer.
Related concept
Standard ACLs match source addresses.
✗
Enable DHCPv6 Guard to block DHCPv6 messages from the secondary router.
Why it's wrong here
Incorrect because DHCPv6 Guard does not affect RAs; it only blocks DHCPv6 server messages.
✗
Use IPv6 Source Guard to filter traffic from the secondary router.
Why it's wrong here
Incorrect because IPv6 Source Guard filters data traffic, not RAs.
✗
Configure the switch to act as a router and send its own RAs with a higher priority to override the secondary router.
Why it's wrong here
Incorrect because this would add another router sending RAs, potentially worsening the instability; RA Guard is the correct tool.

Common exam traps

Common exam trap: ACLs stop at the first match

ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.

Detailed technical explanation

How to think about this question

ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.

KKey Concepts to Remember

Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.

TExam Day Tips

Check inbound versus outbound direction.
Read the ACL from top to bottom.
Look for a broader permit or deny above the intended line.

Key takeaway

ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.

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.

Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related 300-410 ACL questions on filtering logic and placement.

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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 — Standard ACLs match source addresses..

What is the correct answer to this question?

The correct answer is: Configure RA Guard with a policy that includes the primary router's MAC address in the allowed list and apply it to all ports. — RA Guard can be used to allow only authorized routers to send RAs. By configuring an RA Guard policy that permits only the primary router's MAC address, RAs from other routers will be dropped, ensuring stability.

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", "primary". 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?

Standard ACLs match source addresses.

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