- A
The interface is trusted, so Neighbor Discovery messages are not inspected.
Trusted ports bypass ND inspection checks.
- B
The interface only allows Neighbor Advertisements from trusted sources.
Why wrong: Trusted ports allow all ND messages without inspection.
- C
The interface drops all Neighbor Discovery messages.
Why wrong: Trusted ports do not drop ND messages.
- D
The interface requires a valid binding for each ND message.
Why wrong: That is the behavior for untrusted ports.
Question 868 of 2,152
IPv6 ND Inspection trusted-port Command — Effect | Cisco CCNP ENARSI 300-410
This 300-410 practice question tests your understanding of ipv6 first hop security. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
Consider the following partial configuration:
ipv6 nd inspection policy ND_INSPECT device-role host trusted-port
interface GigabitEthernet0/4
ipv6 nd inspection policy ND_INSPECT
What is the effect of the 'trusted-port' command in this policy?
Quick Answer
The answer is that the interface is trusted, so Neighbor Discovery messages are not inspected. This is the correct effect because the `trusted-port` command, when applied within an IPv6 ND inspection policy, explicitly exempts the interface from any validation or filtering of Neighbor Discovery messages, such as Neighbor Solicitations or Router Advertisements. In the context of the Cisco CCNP ENARSI 300-410 exam, this command tests your understanding of how to selectively disable inspection on ports that connect to trusted devices like other routers or switches, preventing false positives in a secure network. A common trap is confusing `trusted-port` with `device-role host`—the former bypasses all ND inspection checks, while the latter still inspects messages but marks the device as a host. For a quick memory tip, think of "trusted-port" as a "skip-inspection pass" for ND traffic, ensuring that only untrusted access ports undergo validation.
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 interface is trusted, so Neighbor Discovery messages are not inspected.
The 'trusted-port' command under the IPv6 ND inspection policy configures the interface to be a trusted port. On a trusted port, Neighbor Discovery (ND) messages are not inspected or rate-limited; they are simply forwarded without validation against the IPv6 neighbor binding table. This is correct because the device-role host setting combined with trusted-port means the interface is considered a legitimate source of ND messages, so no inspection is performed.
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 interface is trusted, so Neighbor Discovery messages are not inspected.
Why this is correct
Trusted ports bypass ND inspection checks.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The interface only allows Neighbor Advertisements from trusted sources.
Why it's wrong here
Trusted ports allow all ND messages without inspection.
- ✗
The interface drops all Neighbor Discovery messages.
Why it's wrong here
Trusted ports do not drop ND messages.
- ✗
The interface requires a valid binding for each ND message.
Why it's wrong here
That is the behavior for untrusted ports.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that 'trusted-port' means the interface is 'trusted to send only valid ND messages' or that it performs some filtering, when in reality it simply disables all ND inspection on that interface.
Detailed technical explanation
How to think about this question
IPv6 First Hop Security (FHS) uses the neighbor binding table to track valid IPv6-to-MAC address mappings. On an untrusted port, ND messages are validated against this table to prevent spoofing attacks (e.g., Neighbor Advertisement spoofing). The 'trusted-port' command is typically applied to interfaces connecting to routers or other trusted infrastructure devices, where ND inspection would cause unnecessary overhead or block legitimate traffic. This aligns with RFC 4861 and Cisco's implementation of RA Guard and ND Inspection.
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.
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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 interface is trusted, so Neighbor Discovery messages are not inspected. — The 'trusted-port' command under the IPv6 ND inspection policy configures the interface to be a trusted port. On a trusted port, Neighbor Discovery (ND) messages are not inspected or rate-limited; they are simply forwarded without validation against the IPv6 neighbor binding table. This is correct because the device-role host setting combined with trusted-port means the interface is considered a legitimate source of ND messages, so no inspection is performed.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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