- A
The binding table shows three entries: one reachable on trusted port, one stale on untrusted port, and one incomplete, indicating active ND learning.
The output correctly shows the state and policy for each entry.
- B
The binding table is empty, indicating no ND activity.
Why wrong: There are three entries, so it is not empty.
- C
The binding table shows all entries as reachable, indicating stable neighbor relationships.
Why wrong: One entry is STALE and one is INCOMP, not all reachable.
- D
The binding table is only for DHCPv6-learned addresses.
Why wrong: The table includes ND-learned addresses, not just DHCPv6.
Question 1,669 of 2,152
Interpreting the IPv6 Binding Table: REACH, STALE, INCOMP States
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.
A network engineer runs the following command to verify IPv6 binding table:
R1# show ipv6 neighbors binding
IPv6 Address Age Link-layer Addr State Interface VLAN Policy 2001:db8::1 10 0011.2233.4455 REACH Fa0/1 10 TRUSTED 2001:db8::2 5 00aa.bbcc.ddee STALE Fa0/0 10 INSPECT 2001:db8::3 0 1111.2222.3333 INCOMP Fa0/0 10 -
What does this output indicate?
Quick Answer
The correct interpretation is that the IPv6 binding table shows three distinct states—REACH, STALE, and INCOMP—each reflecting a different phase of Neighbor Discovery (ND) learning and policy enforcement. The REACH entry on Fa0/1 with a TRUSTED policy indicates an actively verified neighbor with confirmed bidirectional reachability, while the STALE entry on Fa0/0 with an INSPECT policy means the neighbor was once reachable but hasn’t been confirmed within the last 30 seconds, so it remains usable but requires re-validation before forwarding. The INCOMP entry with no policy and a zero age shows an incomplete ND resolution, where a solicitation was sent but no advertisement has been received yet. On the Cisco CCNP ENARSI 300-410 exam, this command tests your ability to read the IPv6 First Hop Security binding table, often used in scenarios involving RA Guard, DHCPv6 Guard, or Source Guard. A common trap is assuming STALE means unreachable—it does not; the entry is still valid until the neighbor cache timeout expires. Memory tip: think of REACH as “ready and confirmed,” STALE as “still standing but needs a handshake,” and INCOMP as “incomplete—still waiting for a reply.”
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 binding table shows three entries: one reachable on trusted port, one stale on untrusted port, and one incomplete, indicating active ND learning.
Option A is correct because the output of 'show ipv6 neighbors binding' displays the IPv6 binding table used in First Hop Security (FHS) features like IPv6 Snooping. The entry for 2001:db8::1 has a REACH state on interface Fa0/1 with a TRUSTED policy, indicating it is reachable on a trusted port. The entry for 2001:db8::2 is STALE on Fa0/0 with an INSPECT policy, meaning it is on an untrusted port and requires verification. The entry for 2001:db8::3 is INCOMP (incomplete) on Fa0/0, showing an ongoing Neighbor Discovery (ND) process where the link-layer address has not yet been resolved.
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 binding table shows three entries: one reachable on trusted port, one stale on untrusted port, and one incomplete, indicating active ND learning.
Why this is correct
The output correctly shows the state and policy for each entry.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The binding table is empty, indicating no ND activity.
Why it's wrong here
There are three entries, so it is not empty.
- ✗
The binding table shows all entries as reachable, indicating stable neighbor relationships.
Why it's wrong here
One entry is STALE and one is INCOMP, not all reachable.
- ✗
The binding table is only for DHCPv6-learned addresses.
Why it's wrong here
The table includes ND-learned addresses, not just DHCPv6.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misinterpretation of the 'show ipv6 neighbors binding' output by confusing it with 'show ipv6 neighbors' (which shows the ND cache), leading candidates to overlook the FHS-specific policy column and state meanings, especially the significance of INCOMP and STALE states in security contexts.
Detailed technical explanation
How to think about this question
The IPv6 binding table is maintained by IPv6 First Hop Security features, such as IPv6 Snooping (RFC 4861-based), which monitors ND messages (NS, NA, RS, RA) to build a database of valid IPv6-to-MAC bindings. The STALE state indicates the entry has not been refreshed within the reachable time (default 30 seconds), and the INCOMP state means a Neighbor Solicitation was sent but no Neighbor Advertisement received, often due to a non-responsive host or spoofing attempt. In real-world deployments, the TRUSTED policy on Fa0/1 might be applied to a router-facing port, while INSPECT on Fa0/0 indicates a host-facing port where ND inspection enforces address ownership to prevent attacks like ND spoofing.
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.
Visual reference
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.
- →
IPv6 First Hop Security — study guide chapter
Learn the concepts, then practise the questions
- →
IPv6 First Hop Security practice questions
Targeted practice on this topic area only
- →
All 300-410 questions
2,152 questions across all exam domains
- →
Cisco CCNP ENARSI 300-410 study guide
Full concept coverage aligned to exam objectives
- →
300-410 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related 300-410 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Layer 3 Technologies practice questions
Practise 300-410 questions linked to Layer 3 Technologies.
EIGRP Troubleshooting practice questions
Practise 300-410 questions linked to EIGRP Troubleshooting.
OSPF Troubleshooting (v2/v3) practice questions
Practise 300-410 questions linked to OSPF Troubleshooting (v2/v3).
BGP Troubleshooting practice questions
Practise 300-410 questions linked to BGP Troubleshooting.
Route Redistribution practice questions
Practise 300-410 questions linked to Route Redistribution.
Policy-Based Routing (PBR) practice questions
Practise 300-410 questions linked to Policy-Based Routing (PBR).
VRF-Lite practice questions
Practise 300-410 questions linked to VRF-Lite.
Route Maps and Route Filtering practice questions
Practise 300-410 questions linked to Route Maps and Route Filtering.
Administrative Distance practice questions
Practise 300-410 questions linked to Administrative Distance.
Route Summarization practice questions
Practise 300-410 questions linked to Route Summarization.
Bidirectional Forwarding Detection (BFD) practice questions
Practise 300-410 questions linked to Bidirectional Forwarding Detection (BFD).
VPN Technologies practice questions
Practise 300-410 questions linked to VPN Technologies.
Practice this exam
Start a free 300-410 practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
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 binding table shows three entries: one reachable on trusted port, one stale on untrusted port, and one incomplete, indicating active ND learning. — Option A is correct because the output of 'show ipv6 neighbors binding' displays the IPv6 binding table used in First Hop Security (FHS) features like IPv6 Snooping. The entry for 2001:db8::1 has a REACH state on interface Fa0/1 with a TRUSTED policy, indicating it is reachable on a trusted port. The entry for 2001:db8::2 is STALE on Fa0/0 with an INSPECT policy, meaning it is on an untrusted port and requires verification. The entry for 2001:db8::3 is INCOMP (incomplete) on Fa0/0, showing an ongoing Neighbor Discovery (ND) process where the link-layer address has not yet been resolved.
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.
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 →
Keep practising
More 300-410 practice questions
- Drag and drop the steps to negotiate an IKEv2 IPsec site-to-site tunnel into the correct order, from first to last.
- Drag and drop the steps to troubleshoot an IPsec site-to-site VPN adjacency failure into the correct order, from first t…
- Drag and drop the steps to verify and validate the operational state of an IPsec site-to-site VPN into the correct order…
- Consider the following configuration snippet: ip cef ! interface GigabitEthernet0/0 ip address 10.0.0.1 255.255.255.25…
- A router is configured with 'logging host 10.1.1.100' and 'logging trap informational'. The engineer notices that syslog…
- Drag and drop the steps to configure a GRE tunnel for IPv6 over IPv4 into the correct order, from first to last.
Last reviewed: Jul 4, 2026
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.