CCNA Network Services and Security Practice Question
Users can browse websites by IP address but not by hostname. The default gateway is reachable and general internet connectivity works. Which two causes are the most likely?
⚠ Common exam trap
A frequent exam trap is to assume that if users cannot browse websites by hostname, the problem must be with routing or the default gateway. However, the question states the default gateway is reachable and general internet connectivity works, which rules out routing issues. Another trap is to confuse unrelated configurations like NTP or switch port settings as causes for DNS failures. The key is to focus on DNS-specific causes: missing DNS server settings on clients or DNS traffic being blocked. Misinterpreting these symptoms leads to incorrect answers that do not address the root cause of hostname resolution failure.
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
✓
The clients are missing a valid DNS server setting
If IP connectivity works but hostnames fail, the problem is usually DNS configuration or DNS reachability, not general routing.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The clients are missing a valid DNS server setting
Why this is correct
Without a valid DNS server setting, the client's resolver has no IP address to send hostname queries to, so name resolution returns a 'server not found' or timeout error. Browsing by IP address works because HTTP requests target the IP directly and never invoke the DNS lookup process. This is a classic missing-DNS configuration issue at the client or DHCP scope.
- ✓
DNS queries may be blocked somewhere along the path
Why this is correct
Even if clients have a correct DNS server address, an intermediate firewall or router ACL can drop UDP/TCP port 53 traffic, preventing queries from reaching the DNS server. Direct IP browsing succeeds because HTTP/HTTPS traffic on ports 80/443 is typically permitted, while DNS-specific packets are silently filtered. This yields the same symptom—hostname lookup fails, IP access works—but the underlying cause is path-based, not client configuration.
- ✗
The routers are missing NTP configuration
Why it's wrong here
NTP configuration only synchronizes clocks on network devices, which is important for logs, monitoring, and certificate validation, but it has no bearing on DNS resolution. A client's ability to resolve a hostname depends on its local resolver and DNS server reachability, not on whether the router's clock is accurate. Therefore, missing NTP would not produce a hostname-only browsing failure.
When this WOULD be correct
In a question where devices fail to authenticate or certificates are rejected, and the symptom is time-related errors (e.g., 'certificate expired' or 'authentication fails'), missing NTP configuration would be a likely cause.
- ✗
The switch access ports should be changed to dynamic desirable
Why it's wrong here
Changing switch access ports to dynamic desirable affects Dynamic Trunking Protocol (DTP) and VLAN trunk negotiation, which is a Layer 2 function. DNS resolution and hostname lookup require Layer 3 reachability and a working DNS client/server path, none of which are influenced by port trunking mode. This option is irrelevant to the symptom and would not restore name resolution.
When this WOULD be correct
This option would be correct in a question about a switch not forming a trunk with another switch, where the access port mode prevents trunk negotiation. For example: 'Two switches fail to establish a trunk link; which configuration change could resolve the issue?'
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.
✓The clients are missing a valid DNS server settingCorrect answer▾
Why this is correct
Without a valid DNS server setting, the client's resolver has no IP address to send hostname queries to, so name resolution returns a 'server not found' or timeout error. Browsing by IP address works because HTTP requests target the IP directly and never invoke the DNS lookup process. This is a classic missing-DNS configuration issue at the client or DHCP scope.
✗The routers are missing NTP configurationWrong answer — click to see why▾
Why this is wrong here
NTP configuration affects time synchronization, not DNS resolution. The issue described (browsing by IP but not hostname) is a DNS problem, not a time synchronization problem.
★ When this WOULD be the correct answer
In a question where devices fail to authenticate or certificates are rejected, and the symptom is time-related errors (e.g., 'certificate expired' or 'authentication fails'), missing NTP configuration would be a likely cause.
Why candidates choose this
Candidates may confuse NTP with DNS because both involve network services, or they might think time sync is required for all network operations, overlooking that DNS is the specific service needed for hostname resolution.
✗The switch access ports should be changed to dynamic desirableWrong answer — click to see why▾
Why this is wrong here
Changing switch access ports to dynamic desirable is related to DTP (Dynamic Trunking Protocol) for trunk negotiation, not DNS resolution. The issue described (browsing by IP but not hostname) points to DNS failure, not switchport mode.
★ When this WOULD be the correct answer
This option would be correct in a question about a switch not forming a trunk with another switch, where the access port mode prevents trunk negotiation. For example: 'Two switches fail to establish a trunk link; which configuration change could resolve the issue?'
Why candidates choose this
Candidates may confuse 'dynamic desirable' with a general 'dynamic' setting that seems like it could fix connectivity, or they might think changing port modes can resolve any network issue without understanding DTP's specific role.
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
Go deeper
Related to this question
Learn chapter
Device File Management with SFTP and SCP
Key term
Fully Qualified Domain Name
A Fully Qualified Domain Name is the complete and unambiguous website or server name that includes the host, domain, and top-level domain, leaving no room for guesswork.
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.
About these practice questions
Courseiva writes every 200-301 question from scratch — 1,389 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or 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 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.