CCNA Network Services and Security Practice Question
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.
⚠ Common exam trap
Cisco exams often test the distinction between DNS client configuration on the router and DNS server records. Do not assume that DNS issues are always due to router misconfiguration; verify the DNS server's records first.
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
✓
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.
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.
- ✗
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 router's DNS client settings are already correct in the scenario—domain lookup is enabled and the name server is set. This option simply re-applies existing configuration and adds no missing DNS records. Even if executed, it would not create the A or PTR entries on the DNS server, so both forward and reverse resolution would still fail.
- ✗
Add only an A record for 'fileserver.courseiva.com' on the DNS server.
Why it's wrong here
Adding only an A record satisfies the forward lookup from fileserver.courseiva.com to 198.51.100.10, but the reverse lookup (PTR) from the IP back to the hostname remains unresolved. Reverse DNS relies on a separate pointer record in the in-addr.arpa zone; without it, a query for 198.51.100.10.in-addr.arpa returns NXDOMAIN. Since the problem requires both directions to work, the PTR record is mandatory, not optional.
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?”
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 |
Go deeper
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Key term
IP address
An IP address is a unique numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication.
Key term
Name Server
A name server is a specialized server that translates human-readable domain names into machine-readable IP addresses so that computers can find each other on a network.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 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 200-301 exam.