Question 1,690 of 2,152

IPv6 First Hop Security →hardMultiple ChoiceObjective-mapped

IPv6 nd suppress — Blocks Forwarded Router Advertisements | Cisco CCNP ENARSI 300-410

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 configures 'ipv6 nd suppress' on a switch port to prevent the switch from sending Router Advertisements. However, after this configuration, hosts on that port cannot obtain IPv6 addresses via SLAAC, even though a router on another port is sending RAs. What is the most likely explanation?

Clue words in this question

Noticing these words before you look at the options changes how you read each choice.

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.

A
The 'ipv6 nd suppress' command blocks all RA traffic on the port, including RAs forwarded from other ports.
Suppress prevents any RA from being sent or forwarded on that port.
B
The router's RAs are being filtered by an ACL on the switch.
Why wrong: No ACL is mentioned.
C
The hosts must be configured to use DHCPv6 instead of SLAAC.
Why wrong: SLAAC should work if RAs are received.
D
The switch port is in a different VLAN than the router.
Why wrong: VLAN mismatch would be a different issue.

Full breakdown with real-world context →

Quick Answer

The answer is that the `ipv6 nd suppress` command blocks all Router Advertisement traffic on the port, including RAs forwarded from other router ports. This occurs because the command is designed to treat the switch port as a host-facing port, which means the switch not only stops sending its own RAs but also suppresses any RAs that would normally be flooded or forwarded from other VLAN interfaces. On the Cisco CCNP ENARSI 300-410 exam, this is a classic trap that tests your understanding of how IPv6 neighbor discovery suppression interacts with Layer 2 forwarding behavior—many engineers mistakenly assume the command only prevents the switch from originating RAs, but it actually drops all RA traffic on that port. A common memory tip is to think of "suppress" as "silence all RA traffic on this port," not just "stop sending." Remember: if you suppress RAs on a port, no router—local or remote—can reach that segment with advertisements.

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 'ipv6 nd suppress' command blocks all RA traffic on the port, including RAs forwarded from other ports.

The 'ipv6 nd suppress' command on a switch port prevents the switch from sending its own Router Advertisements (RAs) and also blocks all incoming RAs from being forwarded out that port. Since SLAAC relies on hosts receiving RAs to learn the prefix and other parameters, blocking the RAs from the router on another port prevents the hosts from obtaining IPv6 addresses via SLAAC.

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.

✓
The 'ipv6 nd suppress' command blocks all RA traffic on the port, including RAs forwarded from other ports.
Why this is correct
Suppress prevents any RA from being sent or forwarded on that port.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The router's RAs are being filtered by an ACL on the switch.
Why it's wrong here
No ACL is mentioned.
✗
The hosts must be configured to use DHCPv6 instead of SLAAC.
Why it's wrong here
SLAAC should work if RAs are received.
✗
The switch port is in a different VLAN than the router.
Why it's wrong here
VLAN mismatch would be a different issue.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Cisco often tests the misconception that 'ipv6 nd suppress' only stops the switch from sending RAs, when in fact it also blocks forwarding of RAs received from other ports, which is the key trap here.

Detailed technical explanation

How to think about this question

The 'ipv6 nd suppress' command is part of Cisco's IPv6 First Hop Security features and is typically applied on switch ports facing hosts to prevent unwanted RA-based attacks. Under the hood, the switch intercepts and drops all RA packets (both sent by the switch and forwarded from other ports) on the suppressed interface, effectively breaking SLAAC for those hosts. In real-world scenarios, this command is used to enforce DHCPv6-only environments or to prevent rogue RAs, but it must be carefully applied to avoid unintentionally blocking legitimate RAs.

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 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.

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: The 'ipv6 nd suppress' command blocks all RA traffic on the port, including RAs forwarded from other ports. — The 'ipv6 nd suppress' command on a switch port prevents the switch from sending its own Router Advertisements (RAs) and also blocks all incoming RAs from being forwarded out that port. Since SLAAC relies on hosts receiving RAs to learn the prefix and other parameters, blocking the RAs from the router on another port prevents the hosts from obtaining IPv6 addresses via SLAAC.

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

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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