- A
MX record
Why wrong: MX records specify mail servers.
- B
CNAME record
Why wrong: CNAME is an alias, not for address resolution.
- C
PTR record
PTR records are used for reverse DNS lookup, which also works with IPv6.
- D
AAAA record
AAAA records map to IPv6 addresses.
- E
A record
Why wrong: A records are for IPv4 addresses.
Question 898 of 1,000
200-901 Network Fundamentals Practice Question
This 200-901 practice question tests your understanding of network fundamentals. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 administrator is configuring a DNS server. Which TWO DNS record types are used for IPv6 address resolution?
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
✓
PTR record
The AAAA record (option D) maps a hostname to a 128-bit IPv6 address, analogous to the A record for IPv4. The PTR record (option C) performs reverse DNS lookup, mapping an IPv6 address to a hostname, which is essential for IPv6 address resolution in scenarios like logging or mail server verification.
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.
- ✗
MX record
Why it's wrong here
MX records specify mail servers.
- ✗
CNAME record
Why it's wrong here
CNAME is an alias, not for address resolution.
- ✓
PTR record
Why this is correct
PTR records are used for reverse DNS lookup, which also works with IPv6.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
AAAA record
Why this is correct
AAAA records map to IPv6 addresses.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
A record
Why it's wrong here
A records are for IPv4 addresses.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between A records (IPv4) and AAAA records (IPv6), and the trap here is that candidates may confuse PTR records as only relevant for IPv4, forgetting that PTR records are equally critical for IPv6 reverse resolution.
Detailed technical explanation
How to think about this question
Under the hood, AAAA records are defined in RFC 3596 and store IPv6 addresses in the DNS zone file, while PTR records for IPv6 use the ip6.arpa domain (per RFC 3152) with nibble format for reverse lookups. In real-world scenarios, misconfigured PTR records for IPv6 can cause email delivery failures due to reverse DNS validation checks by receiving mail servers.
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 junior network technician can log in to a core router but cannot reach the enable prompt or configuration mode. The AAA server is authenticating the login — but the authorisation policy only grants privilege level 1, not 15. Authentication (who you are) is working; authorisation (what you can do) is not.
Visual reference
Quick reference
Common DNS Record Types
| Record | Purpose | Example |
|---|---|---|
| A | IPv4 address mapping | example.com → 93.184.216.34 |
| AAAA | IPv6 address mapping | example.com → 2606:2800::1 |
| CNAME | Alias to another hostname | www → example.com |
| MX | Mail server for domain | example.com → mail.example.com (priority 10) |
| TXT | Text data (SPF, DKIM, verification) | v=spf1 include:_spf.example.com ~all |
| NS | Authoritative name servers | example.com NS ns1.example.com |
| PTR | Reverse DNS (IP → hostname) | 34.216.184.93.in-addr.arpa → example.com |
| SOA | Zone authority record | Primary NS, admin email, serial, TTL defaults |
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this 200-901 question test?
Network Fundamentals — This question tests Network Fundamentals — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: PTR record — The AAAA record (option D) maps a hostname to a 128-bit IPv6 address, analogous to the A record for IPv4. The PTR record (option C) performs reverse DNS lookup, mapping an IPv6 address to a hostname, which is essential for IPv6 address resolution in scenarios like logging or mail server verification.
What should I do if I get this 200-901 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
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Last reviewed: Jul 4, 2026
This 200-901 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 200-901 exam.
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