CCNA Network Services and Security Practice Question
A host receives its IP address automatically but cannot resolve hostnames. Which additional service information is most likely missing from its configuration?
⚠ Common exam trap
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.
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
✓
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.
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
The host's IP address was obtained dynamically, typically via DHCP, and the DHCP offer should also include a DNS server address. Without this DNS resolver entry, the host cannot translate domain names into IP addresses, so any hostname-based request fails. A missing or invalid DNS server address is the direct and correct cause of the resolution failure.
- ✗
A new MAC address
Why it's wrong here
A MAC address is a layer 2 hardware identifier burned into the network interface, used for local frame delivery on the same segment. It plays no role in domain-name resolution, which is a layer 3 function requiring a DNS server IP. Changing the MAC address would only alter the host's LAN identity and would not supply the missing DNS information.
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
A trunk native VLAN is an 802.1Q parameter that specifies which VLAN traffic is sent untagged on a switch trunk link. It is a switch/segment configuration detail and is completely irrelevant to host IP configuration or name resolution. A host connected via an access port never deals with trunk native VLAN settings, so this option cannot fix the DNS issue.
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
An OSPF router ID is a 32-bit value that routers use to uniquely identify themselves in OSPF advertisements and database exchanges. End hosts, such as the one in this scenario, do not run OSPF and have no need for a router ID. Providing a router ID would not give the host a DNS server address, so it would not enable hostname 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
The host's IP address was obtained dynamically, typically via DHCP, and the DHCP offer should also include a DNS server address. Without this DNS resolver entry, the host cannot translate domain names into IP addresses, so any hostname-based request fails. A missing or invalid DNS server address is the direct and correct cause of the resolution failure.
✗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?”
Visual reference
Quick reference
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
Go deeper
Related to this question
Learn chapter
Device File Management with SFTP and SCP
Key term
Subnet mask
A subnet mask is a 32-bit number that helps a computer or network device determine which part of an IP address identifies the network and which part identifies the host device on that network.
Key term
DHCP
Dynamic Host Configuration Protocol (DHCP) automatically assigns IP addresses and network settings to devices on a network, so they can communicate without manual configuration.
About these practice questions
One of 1,389 original 200-301 practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. 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.