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.
A network engineer runs the following command on Router R1:
R1# show ipv6 neighbors
IPv6 Address Age Link-layer Addr State Interface
2001:DB8:1::1 0 aaaa.bbbb.cccc REACH Gi0/0/0
2001:DB8:1::2 10 aaaa.bbbb.cccd STALE Gi0/0/0
2001:DB8:1::3 - aaaa.bbbb.ccce DELAY Gi0/0/1
FE80::1 0 aaaa.bbbb.cccf REACH Gi0/0/0
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The neighbor 2001:DB8:1::3 is in DELAY state, meaning a Neighbor Solicitation will be sent soon.
The neighbor table shows IPv6 neighbors with different states. The entry for 2001:DB8:1::3 has no age (indicated by '-') and is in DELAY state, which means it is waiting for a Neighbor Solicitation to be sent. This could indicate a potential issue with neighbor reachability or a spoofing attempt if the MAC address is unexpected.
Key principle: Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
All neighbors are in a stable state.
Why it's wrong here
The DELAY state indicates a transition; not all are stable.
✓
The neighbor 2001:DB8:1::3 is in DELAY state, meaning a Neighbor Solicitation will be sent soon.
Why this is correct
DELAY state means a NS is pending after a delay timer.
Related concept
Authentication checks who the user is.
✗
The neighbor 2001:DB8:1::2 is unreachable.
Why it's wrong here
STALE state means the entry is valid but not recently verified.
✗
The link-local address FE80::1 is not valid.
Why it's wrong here
It is REACH, so it is valid.
Common exam traps
Common exam trap: authentication is not authorization
Logging in proves the user can authenticate. It does not automatically mean the user is allowed to enter privileged or configuration mode. Watch for AAA authorization, privilege level and command authorization details.
Detailed technical explanation
How to think about this question
This kind of question is testing the difference between identity and permission. A user may successfully log in to a router because authentication is working, but still fail to enter configuration mode because authorization is missing, misconfigured or mapped to a lower privilege level.
KKey Concepts to Remember
Authentication checks who the user is.
Authorization controls what the user is allowed to do after login.
Privilege levels affect access to EXEC and configuration commands.
AAA, TACACS+ and RADIUS can separate login success from command access.
TExam Day Tips
→Do not assume successful login means full administrative access.
→Look for words such as cannot enter configuration mode, privilege level, authorization or command access.
→Separate login problems from permission problems before choosing the answer.
Key takeaway
Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
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.
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 Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related 300-410 questions on access control and AAA configuration.
IPv6 First Hop Security — This question tests IPv6 First Hop Security — Authentication checks who the user is..
What is the correct answer to this question?
The correct answer is: The neighbor 2001:DB8:1::3 is in DELAY state, meaning a Neighbor Solicitation will be sent soon. — The neighbor table shows IPv6 neighbors with different states. The entry for 2001:DB8:1::3 has no age (indicated by '-') and is in DELAY state, which means it is waiting for a Neighbor Solicitation to be sent. This could indicate a potential issue with neighbor reachability or a spoofing attempt if the MAC address is unexpected.
What should I do if I get this 300-410 question wrong?
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related 300-410 questions on access control and AAA configuration.
What is the key concept behind this question?
Authentication checks who the user is.
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