hardMultiple ChoiceObjective-mapped
300-410 Practice Question: The default value of the 'reachable time' in IPv6…
What is the default value of the 'reachable time' in IPv6 Neighbor Discovery (ND) on Cisco IOS-XE?
⚠ Common exam trap
Cisco often tests the distinction between the default value advertised by the router (0, meaning unspecified) and the default value used by hosts (30,000 ms), causing candidates to mistakenly select the host default as the router's advertised value.
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
✓
0 milliseconds (unspecified)
In IPv6 Neighbor Discovery (ND) on Cisco IOS-XE, the default value for the 'reachable time' is 0 milliseconds (unspecified). This means the router does not advertise a specific reachable time in its Router Advertisements (RAs), leaving the receiving hosts to use their own default value (typically 30,000 milliseconds as per RFC 4861). The 'reachable time' is the duration a node considers a neighbor reachable after confirming reachability via Neighbor Solicitation (NS) or Neighbor Advertisement (NA) messages.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
0 milliseconds (unspecified)
Why this is correct
Correct. The default reachable time in the 'ipv6 nd reachable-time' command is 0, meaning no override is sent in RAs.
- ✗
30,000 milliseconds
Why it's wrong here
30,000 milliseconds is the default value used by hosts if not specified, but the Cisco default for the command is 0.
- ✗
60,000 milliseconds
Why it's wrong here
60,000 milliseconds is not the default; it is a possible manual setting.
- ✗
10,000 milliseconds
Why it's wrong here
10,000 milliseconds is not the default; it is a common manual setting.
Go deeper
Related to this question
About these practice questions
This 300-410 question is part of Courseiva's 1,966-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.