The answer is to add an A record for 'fileserver.courseiva.com' pointing to 198.51.100.10 and a PTR record for 198.51.100.10 pointing back to that hostname on the DNS server. This is correct because DNS forward lookup requires an A record to map a hostname to an IP address, while reverse lookup requires a PTR record within the in-addr.arpa zone to map an IP back to a hostname; without both records, nslookup and dig will return NXDOMAIN or no answer. On the CCNA 200-301 v2 exam, this tests your understanding of DNS record types and the distinction between client-side configuration (which is already correct with ip domain-lookup and name-server) versus server-side resource records. A common trap is to try fixing the router’s DNS settings when the real issue is missing records on the server. Remember the mnemonic: “A for Address, PTR for Pointer” — forward needs the name-to-IP map, reverse needs the IP-to-name map.
CCNA Network Services and Security Practice Question
This 200-301 practice question tests your understanding of network services and 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.
Network Topology
You are troubleshooting DNS resolution issues from R1. Using nslookup and dig commands, diagnose why the router cannot resolve the hostname 'fileserver.courseiva.com' to an IP address, and why reverse lookup for IP address 198.51.100.10 fails. Determine the appropriate fix to ensure successful forward and reverse DNS resolution.
R1# show running-config | section ip domain
ip domain lookup
ip name-server 203.0.113.1
ip domain timeout 3
ip domain retry 2
R1# nslookup fileserver.courseiva.com
Translating "fileserver.courseiva.com"...% Unrecognized host or address, or protocol not running.
R1# nslookup 198.51.100.10
Server: 203.0.113.1
Address: 203.0.113.1#53
** server can't find 10.100.51.198.in-addr.arpa: NXDOMAIN
R1# dig fileserver.courseiva.com
; <<>> DiG 9.8.3-P1 <<>> fileserver.courseiva.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 1234
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0
;; QUESTION SECTION:
;fileserver.courseiva.com. IN A
;; AUTHORITY SECTION:
courseiva.com. 3600 IN SOA ns1.courseiva.com. admin.courseiva.com. 2025032101 3600 900 86400 3600
R1# dig -x 198.51.100.10
; <<>> DiG 9.8.3-P1 <<>> -x 198.51.100.10
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 5678
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0
;; QUESTION SECTION:
;10.100.51.198.in-addr.arpa. IN PTR
;; AUTHORITY SECTION:
100.51.198.in-addr.arpa. 3600 IN SOA ns1.courseiva.com. admin.courseiva.com. 2025032101 3600 900 86400 3600
A
Add an A record for 'fileserver.courseiva.com' pointing to 198.51.100.10 and a PTR record for 198.51.100.10 pointing to 'fileserver.courseiva.com' on the DNS server.
The forward lookup fails because the A record is missing (NXDOMAIN), and the reverse lookup fails because the PTR record is missing. Adding both records on the DNS server resolves both issues. R1's DNS configuration is correct; the problem lies with the DNS server's records.
B
Configure the 'ip host' command on R1 to statically map 'fileserver.courseiva.com' to 198.51.100.10.
Why wrong: While this would fix the forward lookup locally, it does not address the reverse lookup failure. Also, the question implies using DNS server records, not static mappings. Static mappings are not a scalable solution for DNS resolution.
C
Enable 'ip domain-lookup' and configure the correct DNS server IP on R1 using 'ip name-server 203.0.113.1'.
Why wrong: The question states that DNS configuration on R1 is already correct (domain-lookup enabled, name-server set). This option describes steps already in place, so it does not fix the issue.
D
Add only an A record for 'fileserver.courseiva.com' on the DNS server.
Why wrong: This fixes the forward lookup but does not address the reverse lookup failure. Both A and PTR records are required for complete DNS resolution.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Add an A record for 'fileserver.courseiva.com' pointing to 198.51.100.10 and a PTR record for 198.51.100.10 pointing to 'fileserver.courseiva.com' on the DNS server.
The DNS resolution failures are due to two issues: the A record for 'fileserver.courseiva.com' does not exist on the DNS server (NXDOMAIN response), and the PTR record for reverse lookup of 198.51.100.10 is missing. To resolve the forward lookup, you must add an A record mapping the hostname to an IP address on the DNS server (e.g., 198.51.100.10). For the reverse lookup, you need to add a PTR record mapping the IP address 198.51.100.10 to the hostname. On R1, the DNS configuration is correct (ip domain-lookup enabled, name-server 203.0.113.1), but the DNS server lacks the necessary records. The solution involves configuring the DNS server (not R1) to add the missing records. On R1, ensure that the DNS server is reachable and that the domain lookup is enabled; no additional CLI changes are required on the router.
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.
✓
Add an A record for 'fileserver.courseiva.com' pointing to 198.51.100.10 and a PTR record for 198.51.100.10 pointing to 'fileserver.courseiva.com' on the DNS server.
Why this is correct
The forward lookup fails because the A record is missing (NXDOMAIN), and the reverse lookup fails because the PTR record is missing. Adding both records on the DNS server resolves both issues. R1's DNS configuration is correct; the problem lies with the DNS server's records.
Related concept
Read the scenario before looking for a memorised answer.
✗
Configure the 'ip host' command on R1 to statically map 'fileserver.courseiva.com' to 198.51.100.10.
Why it's wrong here
While this would fix the forward lookup locally, it does not address the reverse lookup failure. Also, the question implies using DNS server records, not static mappings. Static mappings are not a scalable solution for DNS resolution.
✗
Enable 'ip domain-lookup' and configure the correct DNS server IP on R1 using 'ip name-server 203.0.113.1'.
Why it's wrong here
The question states that DNS configuration on R1 is already correct (domain-lookup enabled, name-server set). This option describes steps already in place, so it does not fix the issue.
✗
Add only an A record for 'fileserver.courseiva.com' on the DNS server.
Why it's wrong here
This fixes the forward lookup but does not address the reverse lookup failure. Both A and PTR records are required for complete DNS resolution.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓Add an A record for 'fileserver.courseiva.com' pointing to 198.51.100.10 and a PTR record for 198.51.100.10 pointing to 'fileserver.courseiva.com' on the DNS server.Correct answer▾
Why this is correct
The forward lookup fails because the A record is missing (NXDOMAIN), and the reverse lookup fails because the PTR record is missing. Adding both records on the DNS server resolves both issues. R1's DNS configuration is correct; the problem lies with the DNS server's records.
✗Configure the 'ip host' command on R1 to statically map 'fileserver.courseiva.com' to 198.51.100.10.Wrong answer — click to see why▾
Why this is wrong here
The 'ip host' command creates a static host table entry on the router, bypassing DNS. It does not fix reverse lookup and is not the intended solution for missing DNS records.
Why candidates choose this
Candidates may think static mapping is a quick fix for hostname resolution, but it does not resolve the underlying DNS server issue and does not help with reverse lookups.
✗Enable 'ip domain-lookup' and configure the correct DNS server IP on R1 using 'ip name-server 203.0.113.1'.Wrong answer — click to see why▾
Why this is wrong here
The problem is not with R1's DNS client configuration but with missing records on the DNS server. Repeating correct configuration does not resolve the missing records.
Why candidates choose this
Candidates often assume DNS issues are due to misconfigured routers, so they focus on router CLI commands rather than checking the DNS server records.
✗Add only an A record for 'fileserver.courseiva.com' on the DNS server.Wrong answer — click to see why▾
Why this is wrong here
Reverse lookup requires a PTR record. Without it, the reverse query for 198.51.100.10 will still fail.
Why candidates choose this
Candidates may focus only on the forward lookup issue and overlook the reverse lookup requirement, especially if the question mentions both failures.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 200-301 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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 200-301 question in full detail.
Identify which 200-301 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Network Services and Security — This question tests Network Services and Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Add an A record for 'fileserver.courseiva.com' pointing to 198.51.100.10 and a PTR record for 198.51.100.10 pointing to 'fileserver.courseiva.com' on the DNS server. — The DNS resolution failures are due to two issues: the A record for 'fileserver.courseiva.com' does not exist on the DNS server (NXDOMAIN response), and the PTR record for reverse lookup of 198.51.100.10 is missing. To resolve the forward lookup, you must add an A record mapping the hostname to an IP address on the DNS server (e.g., 198.51.100.10). For the reverse lookup, you need to add a PTR record mapping the IP address 198.51.100.10 to the hostname. On R1, the DNS configuration is correct (ip domain-lookup enabled, name-server 203.0.113.1), but the DNS server lacks the necessary records. The solution involves configuring the DNS server (not R1) to add the missing records. On R1, ensure that the DNS server is reachable and that the domain lookup is enabled; no additional CLI changes are required on the router.
What should I do if I get this 200-301 question wrong?
Identify which 200-301 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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