CCNA Network Services and Security Practice Question
This 200-301 practice question tests your understanding of network services and security. 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. A key principle to apply: dNS servers translate human-readable hostnames into IP addresses, enabling hostname-based network communication.. 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.
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?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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.
Key principle: DNS servers translate human-readable hostnames into IP addresses, enabling hostname-based network communication.
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
Name resolution will fail if clients do not know where to send DNS queries.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
DNS servers translate human-readable hostnames into IP addresses, enabling hostname-based network communication.
✓
DNS queries may be blocked somewhere along the path
Why this is correct
If UDP/TCP 53 traffic is filtered, hostnames fail while direct IP access can still work.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
DNS servers translate human-readable hostnames into IP addresses, enabling hostname-based network communication.
✗
The routers are missing NTP configuration
Why it's wrong here
Time sync is useful operationally but does not cause hostname-only failure.
✗
The switch access ports should be changed to dynamic desirable
Why it's wrong here
DTP settings do not explain name resolution failure.
Common exam traps
Common exam trap: answer the scenario, not the keyword
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.
Detailed technical explanation
How to think about this question
DNS (Domain Name System) is a critical IP service that maps human-friendly hostnames to IP addresses, allowing users to access resources by name rather than numeric IPs. In Cisco networks and the CCNA context, DNS resolution is essential for both end-user devices and network devices that rely on hostname resolution for management and connectivity. Without DNS, devices cannot translate domain names into IP addresses, causing failures in hostname-based browsing.
When users can reach the default gateway and access the internet by IP address but not by hostname, the problem typically lies in DNS configuration or DNS traffic reachability. Clients must be configured with at least one valid DNS server IP address to send queries. Additionally, network devices, including routers and firewalls, must permit DNS traffic on UDP and TCP port 53. If DNS queries are blocked or filtered, the hostname resolution process fails even though IP routing remains functional.
A common exam trap is to confuse general IP connectivity issues with DNS problems. The presence of successful ping to the default gateway and IP-based browsing confirms routing is working, so the problem is not with routing protocols or gateway configuration. Instead, the issue is DNS-specific, such as missing DNS server settings on clients or blocked DNS traffic. Practically, network administrators must verify DNS server IPs on clients and ensure no ACLs or firewall rules block DNS traffic to maintain hostname resolution.
KKey Concepts to Remember
DNS servers translate human-readable hostnames into IP addresses, enabling hostname-based network communication.
Clients must have a valid DNS server IP configured to resolve hostnames; missing this setting causes hostname resolution failure.
Network devices and firewalls must allow DNS traffic (UDP and TCP port 53) to ensure DNS queries and responses are not blocked.
If DNS queries are blocked, users can still access websites by IP address but cannot resolve hostnames to IPs.
The default gateway being reachable confirms basic IP routing is functional but does not guarantee DNS functionality.
DNS resolution failures are distinct from routing issues; routing problems affect all IP connectivity, not just hostname resolution.
Cisco devices rely on proper DNS configuration for services like Cisco IOS name resolution and troubleshooting commands.
Blocking DNS traffic or misconfiguring DNS settings are common causes of hostname-only connectivity issues in Cisco network environments.
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
DNS servers translate human-readable hostnames into IP addresses, enabling hostname-based network communication.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 200-301 question in full detail.
Review dNS servers translate human-readable hostnames into IP addresses, enabling hostname-based network communication., then practise related 200-301 questions on the same topic to reinforce the concept.
Network Services and Security — This question tests Network Services and Security — DNS servers translate human-readable hostnames into IP addresses, enabling hostname-based network communication..
What is the correct answer to this question?
The correct answer is: 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.
What should I do if I get this 200-301 question wrong?
Review dNS servers translate human-readable hostnames into IP addresses, enabling hostname-based network communication., then practise related 200-301 questions on the same topic to reinforce the concept.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
DNS servers translate human-readable hostnames into IP addresses, enabling hostname-based network communication.
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