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. A key principle to apply: a host requires a DNS server address to resolve hostnames into IP addresses for network communication using names rather than numeric IPs.. 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 host receives its IP address automatically but cannot resolve hostnames. Which additional service information is most likely missing from its configuration?
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
✓
A DNS server address
If the host receives an IP address but cannot resolve hostnames, the most likely missing information is a DNS server setting. In plain language, the device has enough configuration to join the network but not enough to ask where hostnames map in IP terms. DHCP can provide this DNS server information automatically, and if it is missing, the host may still communicate by IP while failing on names.
This is a common service-troubleshooting pattern because it separates address configuration from name resolution. The correct answer is the missing DNS-related setting rather than the IP address itself or the subnet mask.
Key principle: A host requires a DNS server address to resolve hostnames into IP addresses for network communication using names rather than numeric IPs.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
A DNS server address
Why this is correct
This is correct because DNS service information is needed for hostname resolution.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
A host requires a DNS server address to resolve hostnames into IP addresses for network communication using names rather than numeric IPs.
✗
A new MAC address
Why it's wrong here
This is wrong because changing the MAC address does not solve hostname resolution.
When this WOULD be correct
If the exam question were about a scenario where a host is unable to connect to the network due to a hardware issue, such as a MAC address conflict or a requirement for a specific MAC address for network access control, then selecting a new MAC address could be correct.
✗
A trunk native VLAN
Why it's wrong here
This is wrong because host name-resolution failure is not caused by native VLAN configuration in this context.
When this WOULD be correct
In a question about configuring a switch for VLANs, if the scenario involves ensuring that a specific VLAN is set as the native VLAN for trunk ports, then selecting 'A trunk native VLAN' would be correct. This would be relevant in a context where VLAN tagging and traffic management are being discussed.
✗
An OSPF router ID
Why it's wrong here
This is wrong because hosts do not need OSPF router IDs for name resolution.
When this WOULD be correct
In a question asking about OSPF configuration issues, where a router is unable to establish OSPF neighbor relationships due to misconfiguration, the absence of a proper OSPF router ID would be the correct answer, as it is essential for OSPF operation.
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.
✓A DNS server addressCorrect answer▾
Why this is correct
This is correct because DNS service information is needed for hostname resolution.
✗A new MAC addressWrong answer — click to see why▾
Why this is wrong here
A MAC address is a hardware identifier used for local network communication; it does not affect hostname resolution. Changing the MAC address would not provide DNS service information.
★ When this WOULD be the correct answer
If the exam question were about a scenario where a host is unable to connect to the network due to a hardware issue, such as a MAC address conflict or a requirement for a specific MAC address for network access control, then selecting a new MAC address could be correct.
Why candidates choose this
Students might think that a new MAC address could resolve connectivity issues, confusing it with scenarios where MAC address filtering or duplication causes network problems.
✗A trunk native VLANWrong answer — click to see why▾
Why this is wrong here
A trunk native VLAN is a switch configuration for VLAN tagging on trunk ports; it is irrelevant to a host's ability to resolve hostnames. Hostname resolution requires DNS, not VLAN settings.
★ When this WOULD be the correct answer
In a question about configuring a switch for VLANs, if the scenario involves ensuring that a specific VLAN is set as the native VLAN for trunk ports, then selecting 'A trunk native VLAN' would be correct. This would be relevant in a context where VLAN tagging and traffic management are being discussed.
Why candidates choose this
Test-takers might associate VLANs with network segmentation and incorrectly assume that misconfigured VLANs could affect name resolution, especially if they confuse layer 2 and layer 3 issues.
✗An OSPF router IDWrong answer — click to see why▾
Why this is wrong here
OSPF router IDs are used by routers in OSPF routing protocol operations; hosts do not participate in OSPF and do not need a router ID for name resolution.
★ When this WOULD be the correct answer
In a question asking about OSPF configuration issues, where a router is unable to establish OSPF neighbor relationships due to misconfiguration, the absence of a proper OSPF router ID would be the correct answer, as it is essential for OSPF operation.
Why candidates choose this
Students may confuse routing protocols with DNS, thinking that a router ID is needed for the host to communicate with a DNS server, but DNS is an application-layer service independent of OSPF.
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
A frequent exam trap is assuming that if a host receives an IP address via DHCP, it automatically has all necessary network information, including DNS server addresses. This mistake overlooks that DHCP can provide IP address and subnet mask without DNS settings. Candidates might incorrectly select options related to MAC address changes, VLAN configurations, or routing protocols like OSPF, which do not affect hostname resolution. The trap is confusing IP connectivity with name resolution, leading to wrong answers that ignore the essential role of DNS in translating hostnames to IP addresses.
Detailed technical explanation
How to think about this question
DNS (Domain Name System) is a critical IP service that translates human-readable hostnames into IP addresses, enabling users and applications to access network resources by name. When a host obtains its IP configuration via DHCP, it typically receives not only its IP address and subnet mask but also the DNS server addresses needed for hostname resolution. Without DNS server information, the host cannot convert domain names into IP addresses, which prevents it from accessing services by name.
In Cisco networking and the CCNA context, DHCP is the primary protocol used to automate IP configuration, including DNS server assignment. If a host receives an IP address but lacks DNS server details, it can communicate using IP addresses directly but fails when attempting to resolve hostnames. This distinction is important because IP addressing and DNS are separate components of IP services. The DHCP server must be configured to provide DNS information, or the host must be manually configured with DNS server addresses to enable full functionality.
A common exam trap is confusing IP address assignment with DNS configuration. Candidates may assume that receiving an IP address automatically means all necessary network information is present. However, DNS is a separate service that must be explicitly provided. Practically, a host without DNS can ping IP addresses but cannot browse websites or access network resources by name. Understanding this separation helps troubleshoot connectivity issues and correctly answer CCNA questions focused on IP services and DNS.
KKey Concepts to Remember
A host requires a DNS server address to resolve hostnames into IP addresses for network communication using names rather than numeric IPs.
DHCP can provide IP address, subnet mask, default gateway, and DNS server information, but missing DNS settings prevent hostname resolution despite having an IP address.
Hostname resolution depends on DNS service information, which translates human-friendly names into routable IP addresses within Cisco network environments.
Without a DNS server address, a host can communicate using IP addresses but cannot resolve domain names, causing failures in applications relying on hostname resolution.
OSPF router ID configuration is unrelated to host-level DNS resolution and primarily affects routing protocol operations on routers, not end hosts.
A trunk native VLAN setting affects VLAN tagging on switches and does not influence a host’s ability to resolve hostnames via DNS.
Changing a host’s MAC address does not impact DNS resolution because MAC addresses operate at Layer 2 and DNS operates at Layer 7 of the OSI model.
Proper IP services configuration requires both IP addressing and DNS server information to enable full network connectivity and name resolution.
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
A host requires a DNS server address to resolve hostnames into IP addresses for network communication using names rather than numeric IPs.
Real-world example
How this comes up in practice
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
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 a host requires a DNS server address to resolve hostnames into IP addresses for network communication using names rather than numeric IPs., 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 — A host requires a DNS server address to resolve hostnames into IP addresses for network communication using names rather than numeric IPs..
What is the correct answer to this question?
The correct answer is: A DNS server address — If the host receives an IP address but cannot resolve hostnames, the most likely missing information is a DNS server setting. In plain language, the device has enough configuration to join the network but not enough to ask where hostnames map in IP terms. DHCP can provide this DNS server information automatically, and if it is missing, the host may still communicate by IP while failing on names.
This is a common service-troubleshooting pattern because it separates address configuration from name resolution. The correct answer is the missing DNS-related setting rather than the IP address itself or the subnet mask.
What should I do if I get this 200-301 question wrong?
Review a host requires a DNS server address to resolve hostnames into IP addresses for network communication using names rather than numeric IPs., 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?
A host requires a DNS server address to resolve hostnames into IP addresses for network communication using names rather than numeric IPs.
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