- A
Option 6 (Domain Name Server)
Why wrong: Option 6 is for DHCPv4, not DHCPv6.
- B
Option 23 (DNS Recursive Name Server)
Option 23 is the DHCPv6 option for DNS servers.
- C
Option 24 (Domain Search List)
Why wrong: Option 24 is for domain search list, not DNS server addresses.
- D
Option 21 (SIP Server Domain Name)
Why wrong: Option 21 is for SIP servers, not DNS.
Question 1,471 of 2,152
DHCPv6 DNS Recursive Name Server Option 23
This 300-410 practice question tests your understanding of dhcp (ipv4 and ipv6). Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
Which DHCPv6 option carries the DNS recursive name server information?
Quick Answer
The answer is DHCPv6 Option 23, the DNS Recursive Name Server option. This option is correct because it carries the list of DNS server addresses that DHCPv6 clients use for name resolution, as defined in RFC 3646. When a client requests network configuration, the DHCPv6 server includes Option 23 to provide one or more IPv6 addresses of recursive name servers, enabling the client to resolve domain names without needing to manually configure DNS. On the Cisco CCNP ENARSI 300-410 exam, this topic tests your understanding of DHCPv6 operations and the specific options used for stateless and stateful address configuration. A common trap is confusing Option 23 with Option 24 (Domain Search List), which provides domain suffixes rather than server addresses. Remember the memory tip: "23 for DNS servers, 24 for search domains" — think of the number 23 as the two letters "D" and "N" in the alphabet (D=4, N=14, sum 18, but close enough to anchor the concept that Option 23 is the one that gives you the DNS server list).
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
✓
Option 23 (DNS Recursive Name Server)
Option B is correct because DHCPv6 Option 23 (DNS Recursive Name Server) is specifically defined in RFC 3646 to carry the IPv6 addresses of DNS recursive name servers to DHCPv6 clients. This is the standard mechanism for IPv6 hosts to learn DNS server addresses via DHCPv6, analogous to DHCPv4 Option 6 for IPv4.
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.
- ✗
Option 6 (Domain Name Server)
Why it's wrong here
Option 6 is for DHCPv4, not DHCPv6.
- ✓
Option 23 (DNS Recursive Name Server)
Why this is correct
Option 23 is the DHCPv6 option for DNS servers.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Option 24 (Domain Search List)
Why it's wrong here
Option 24 is for domain search list, not DNS server addresses.
- ✗
Option 21 (SIP Server Domain Name)
Why it's wrong here
Option 21 is for SIP servers, not DNS.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between DHCPv4 Option 6 and DHCPv6 Option 23, trapping candidates who assume the same option number applies to both protocols.
Detailed technical explanation
How to think about this question
DHCPv6 Option 23 contains one or more 128-bit IPv6 addresses of DNS recursive name servers, which the client uses for DNS resolution. Unlike DHCPv4, DHCPv6 uses a stateless or stateful model, and Option 23 is often used in conjunction with Option 24 (Domain Search List) to provide complete DNS configuration. In real-world deployments, misconfigured Option 23 can cause IPv6 DNS resolution failures even if IPv6 connectivity is working.
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 practitioner preparing for the 300-410 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Visual reference
What to study next
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FAQ
Questions learners often ask
What does this 300-410 question test?
DHCP (IPv4 and IPv6) — This question tests DHCP (IPv4 and IPv6) — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Option 23 (DNS Recursive Name Server) — Option B is correct because DHCPv6 Option 23 (DNS Recursive Name Server) is specifically defined in RFC 3646 to carry the IPv6 addresses of DNS recursive name servers to DHCPv6 clients. This is the standard mechanism for IPv6 hosts to learn DNS server addresses via DHCPv6, analogous to DHCPv4 Option 6 for IPv4.
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
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.
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