This 300-410 practice question tests your understanding of ipv6 first hop security. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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 enables 'ipv6 destination guard' on a switch to prevent IPv6 address spoofing. After configuration, a legitimate host on a port is unable to receive traffic from the network, although it can send traffic. The host has a global unicast address. The switch logs show that destination guard is dropping packets destined to that host. What is the most likely cause?
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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The host uses IPv6 privacy extensions and changes its address frequently, but the binding table only has the original address.
IPv6 Destination Guard validates destination addresses against the binding table. If the host's address is not in the binding table (e.g., because the host did not send an NA or the binding timed out), the switch drops packets destined to that address. The edge case is that Destination Guard requires the binding to be in 'REACHABLE' state. If the host is silent for a long time, the binding may become 'STALE' and eventually 'DELAY' or 'PROBE', but Destination Guard still accepts traffic as long as the binding exists. However, if the binding is removed due to a timeout or if the host's address was never learned (e.g., the host uses privacy extensions and changes its address frequently), Destination Guard will drop traffic. The most likely oversight is that the host uses temporary addresses (privacy extensions) that are not registered in the binding table because the switch only learns the initial address from the first NA.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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 host uses IPv6 privacy extensions and changes its address frequently, but the binding table only has the original address.
Why this is correct
Destination Guard relies on static bindings; privacy addresses are not learned.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
Destination Guard blocks all global unicast addresses by default.
Why it's wrong here
It only blocks addresses not in the binding table.
✗
The switch port is not configured as 'trusted' for destination guard.
Why it's wrong here
Destination Guard does not have a trust concept.
✗
The host is using a link-local address, which destination guard does not support.
Why it's wrong here
Destination Guard works with all unicast addresses.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 300-410 question in full detail.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 300-410 NAT questions on configuration and troubleshooting.
IPv6 First Hop Security — This question tests IPv6 First Hop Security — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: The host uses IPv6 privacy extensions and changes its address frequently, but the binding table only has the original address. — IPv6 Destination Guard validates destination addresses against the binding table. If the host's address is not in the binding table (e.g., because the host did not send an NA or the binding timed out), the switch drops packets destined to that address. The edge case is that Destination Guard requires the binding to be in 'REACHABLE' state. If the host is silent for a long time, the binding may become 'STALE' and eventually 'DELAY' or 'PROBE', but Destination Guard still accepts traffic as long as the binding exists. However, if the binding is removed due to a timeout or if the host's address was never learned (e.g., the host uses privacy extensions and changes its address frequently), Destination Guard will drop traffic. The most likely oversight is that the host uses temporary addresses (privacy extensions) that are not registered in the binding table because the switch only learns the initial address from the first NA.
What should I do if I get this 300-410 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 300-410 NAT questions on configuration and troubleshooting.
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?
Static NAT maps one inside address to one outside address.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
This 300-410 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 300-410 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.