Question 1,280 of 2,152

IPv6 First Hop Security →easyMultiple ChoiceObjective-mapped

RFC 4861: IPv6 Neighbor Discovery Protocol Definition

This 300-410 practice question tests your understanding of ipv6 first hop security. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.

Which RFC defines the IPv6 Neighbor Discovery Protocol that is the basis for many First Hop Security features?

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
RFC 4861
RFC 4861 is the standard for IPv6 Neighbor Discovery.
B
RFC 2460
Why wrong: RFC 2460 defines the IPv6 base protocol.
C
RFC 4291
Why wrong: RFC 4291 defines IPv6 addressing architecture.
D
RFC 4443
Why wrong: RFC 4443 defines ICMPv6.

Full breakdown with real-world context →

Quick Answer

The answer is RFC 4861, which defines the IPv6 Neighbor Discovery Protocol (NDP). This protocol is the correct choice because it establishes the core mechanisms for node-to-node communication on a local IPv6 link, including Neighbor Solicitations, Neighbor Advertisements, Router Solicitations, and Router Advertisements. These messages form the foundation for many First Hop Security features, such as RA Guard and ND Inspection, which are critical for mitigating spoofing and man-in-the-middle attacks. On the Cisco CCNP ENARSI 300-410 exam, you will often see this tested in the context of IPv6 security and troubleshooting, where a common trap is confusing RFC 4861 with RFC 2460 (which defines the IPv6 header) or RFC 4443 (ICMPv6). A reliable memory tip is to think of "4861" as "4-8-6-1" where "ND" (Neighbor Discovery) uses ICMPv6 types 133-137, and the number 4861 is the only RFC that covers all four message types in one document.

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

✓

RFC 4861

RFC 4861 defines the IPv6 Neighbor Discovery Protocol (NDP), which is the foundation for IPv6 First Hop Security (FHS) features. NDP replaces ARP in IPv6 and provides address resolution, router discovery, neighbor unreachability detection, and redirect functions, all of which are leveraged by FHS mechanisms like RA Guard, DHCPv6 Guard, and Source Address Validation Improvement (SAVI).

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.

✓
RFC 4861
Why this is correct
RFC 4861 is the standard for IPv6 Neighbor Discovery.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
RFC 2460
Why it's wrong here
RFC 2460 defines the IPv6 base protocol.
✗
RFC 4291
Why it's wrong here
RFC 4291 defines IPv6 addressing architecture.
✗
RFC 4443
Why it's wrong here
RFC 4443 defines ICMPv6.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Cisco often tests the distinction between the RFC that defines the protocol itself (RFC 4861 for NDP) versus RFCs that define supporting technologies like ICMPv6 (RFC 4443) or addressing (RFC 4291), leading candidates to confuse the foundational RFC with related but separate standards.

Detailed technical explanation

How to think about this question

NDP uses five ICMPv6 message types: Neighbor Solicitation (NS), Neighbor Advertisement (NA), Router Solicitation (RS), Router Advertisement (RA), and Redirect. FHS features like RA Guard rely on filtering rogue RA messages at the switch level, while SAVI tracks the binding of IPv6 addresses to MAC addresses using NDP snooping to prevent spoofing attacks. In real-world deployments, misconfigured NDP can lead to neighbor cache exhaustion or man-in-the-middle attacks via rogue 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 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.

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: RFC 4861 — RFC 4861 defines the IPv6 Neighbor Discovery Protocol (NDP), which is the foundation for IPv6 First Hop Security (FHS) features. NDP replaces ARP in IPv6 and provides address resolution, router discovery, neighbor unreachability detection, and redirect functions, all of which are leveraged by FHS mechanisms like RA Guard, DHCPv6 Guard, and Source Address Validation Improvement (SAVI).

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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