CCNA Network Services and Security Practice Question
A host can reach remote websites by IP address but fails when using their hostnames. Which missing configuration item is the strongest suspect?
⚠ Common exam trap
Cisco often tests the distinction between Layer 3 connectivity (IP reachability) and application-layer services (DNS), so the trap here is that candidates might suspect a routing or switching issue (like a missing default gateway or VLAN mismatch) when the symptom clearly isolates the problem to name resolution.
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
When a host can reach remote websites by IP address but not by hostname, the issue is that the host cannot resolve the hostname to an IP address. DNS (Domain Name System) is responsible for this resolution, and if the DNS server address is missing or misconfigured on the host, name resolution fails. This is the strongest suspect because all other network connectivity (routing, switching) is functional, as proven by successful IP-based access.
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 DNS server address is the resource the host uses to send name-resolution queries; without a valid address, the resolver cannot translate hostnames like www.example.com into IP addresses. Since the host can already reach remote websites by literal IP address, the only missing piece is the ability to map names to addresses. Verify that DHCP delivers a correct DNS server or manually configure one, and confirm the DNS server itself is reachable and responsive.
- ✗
A new MAC address
Why it's wrong here
A host that reaches remote websites by IP address already has Layer 3 connectivity and routing in place; changing its MAC address would only alter the Layer 2 hardware identifier used for local delivery. MAC addresses are resolved through ARP, not DNS, so this would have no effect on hostname-to-IP translation. If DNS resolution is failing, the cause is more likely a missing or incorrect DNS server setting, not the physical network interface address.
When this WOULD be correct
In a question about a network security scenario where a device's MAC address has changed due to a network policy update, and the question asks about connectivity issues related to access control lists (ACLs) or MAC filtering, a new MAC address could be the correct answer if it is preventing access to certain resources.
- ✗
A trunk native VLAN
Why it's wrong here
A trunk native VLAN is a Layer 2 switch configuration parameter that defines which VLAN carries untagged frames on a trunk port between switches. It has no bearing on end-host name resolution, which is an application-layer function using DNS. If a native VLAN mismatch existed, it would cause connectivity problems such as spanning-tree or frame-tagging anomalies, not a selective failure to resolve hostnames while IP connectivity works.
When this WOULD be correct
In a scenario where a question asks about VLAN configuration affecting inter-VLAN communication or switch port settings, a candidate might need to identify the correct native VLAN for trunk ports to ensure proper traffic flow between VLANs, making this option correct.
- ✗
An OSPF router ID
Why it's wrong here
OSPF router IDs are selected by routers to identify themselves in OSPF protocol messages and to ensure stable LSDB synchronization; they are meaningless to an end host performing DNS lookups. Even if the host ran OSPF, the router ID does not participate in name resolution. The symptom of IP connectivity working but hostname lookup failing points exclusively to the DNS client configuration.
When this WOULD be correct
If the question were about troubleshooting OSPF routing issues, such as a failure to establish neighbor relationships or route advertisement problems, then identifying the correct OSPF router ID would be crucial for proper network communication.
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 DNS server address is the resource the host uses to send name-resolution queries; without a valid address, the resolver cannot translate hostnames like www.example.com into IP addresses. Since the host can already reach remote websites by literal IP address, the only missing piece is the ability to map names to addresses. Verify that DHCP delivers a correct DNS server or manually configure one, and confirm the DNS server itself is reachable and responsive.
✗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 at Layer 2, and it has no role in hostname resolution. Changing the MAC address would not affect the ability to resolve hostnames to IP addresses.
★ When this WOULD be the correct answer
In a question about a network security scenario where a device's MAC address has changed due to a network policy update, and the question asks about connectivity issues related to access control lists (ACLs) or MAC filtering, a new MAC address could be the correct answer if it is preventing access to certain resources.
Why candidates choose this
Students might confuse MAC addresses with IP addresses or think that network connectivity issues at Layer 2 could impact name resolution, but DNS operates at Layer 3 and above.
✗A trunk native VLANWrong answer — click to see why▾
Why this is wrong here
A trunk native VLAN is a configuration for switch ports that carry multiple VLANs, and it is unrelated to hostname resolution. The symptom described is a DNS issue, not a VLAN or trunking problem.
★ When this WOULD be the correct answer
In a scenario where a question asks about VLAN configuration affecting inter-VLAN communication or switch port settings, a candidate might need to identify the correct native VLAN for trunk ports to ensure proper traffic flow between VLANs, making this option correct.
Why candidates choose this
Test-takers might associate VLANs with network segmentation and think that misconfigurations could prevent hostname resolution, but DNS is a separate service that does not depend on VLAN settings.
✗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, not by end hosts. End hosts do not participate in OSPF and do not require a router ID for any function, including name resolution.
★ When this WOULD be the correct answer
If the question were about troubleshooting OSPF routing issues, such as a failure to establish neighbor relationships or route advertisement problems, then identifying the correct OSPF router ID would be crucial for proper network communication.
Why candidates choose this
Students might confuse OSPF with DNS or think that routing protocols are involved in name resolution, but DNS is an application-layer service independent of routing protocols.
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?”
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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.