DNS Resolution Failure: Browsing by IP Works but Not Hostname
Exhibit
Client tests: - ping 172.16.20.50 = success - open http://172.16.20.50 = success - open http://portal.corp.example = fail
Based on the exhibit, what is the strongest explanation for why clients can browse by IP address but not by hostname?
Quick Answer
The answer is a DNS failure or DNS configuration problem, because successful browsing by IP address proves that IP connectivity and the network path to the destination are fully functional. When the same service fails only by hostname, the issue is isolated to name resolution, meaning the client cannot translate the domain name into an IP address, even though routing, switching, and raw connectivity are working. On the CCNA 200-301 v2 exam, this scenario tests your ability to differentiate between Layer 3 connectivity problems and application-layer naming issues, often appearing in troubleshooting questions where a single exhibit shows a ping to an IP succeeding but a ping to a hostname failing. A common trap is to blame routing or ACLs, but the key insight is that if IP works, the path is fine—only the DNS lookup is broken. Memory tip: “IP works, name fails? DNS nails it.”
⚠ Common exam trap
A frequent exam trap is assuming that if hostname resolution fails, the problem must be with routing or VLAN configurations such as the default gateway or switch trunk native VLAN. However, since clients can browse by IP address, these path elements are functioning correctly. Misattributing the failure to routing or VLAN issues wastes time and leads to incorrect answers. The key mistake is not recognizing that DNS operates at a higher layer and that name resolution failures are distinct from IP connectivity problems.
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
✓
Name resolution is failing even though IP connectivity works.
The strongest explanation is a DNS failure or DNS configuration problem. In practical terms, successful browsing by IP address shows that the client can already reach the destination over the network path. When the same service fails only by hostname, the issue is much more likely in name resolution than in routing, switching, or raw connectivity. This is one of the most useful support patterns because it quickly separates path problems from naming problems.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Name resolution is failing even though IP connectivity works.
Why this is correct
This is correct because the difference between IP success and hostname failure points to DNS.
- ✗
The client has the wrong default gateway.
Why it's wrong here
This is wrong because the client can already reach the server by IP.
When this WOULD be correct
In a different scenario where a client is unable to connect to any external resources, including both IP and hostname, the question might ask why the client cannot access the internet. In that case, if the default gateway is misconfigured, it would be the correct answer as it would block all traffic.
- ✗
The switch trunk native VLAN is wrong.
Why it's wrong here
This is wrong because the symptom is specifically name-based failure, not a total path failure.
When this WOULD be correct
In a different scenario, if the question involved a network where clients are unable to communicate across VLANs due to misconfigured trunk settings, and the context indicated that hostname resolution relies on inter-VLAN routing, then this option could be correct.
- ✗
The server must run PPP before hostnames can work.
Why it's wrong here
This is wrong because PPP is unrelated to DNS-based service access here.
When this WOULD be correct
In a scenario where the question asks about the necessity of specific protocols for establishing network connections, such as a question about how to configure a network for dial-up connections, this option could be correct if it stated that PPP is required for establishing a connection before DNS queries can be made.
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.
✓Name resolution is failing even though IP connectivity works.Correct answer▾
Why this is correct
This is correct because the difference between IP success and hostname failure points to DNS.
✗The client has the wrong default gateway.Wrong answer — click to see why▾
Why this is wrong here
This option is incorrect because having the wrong default gateway would typically prevent any connectivity, including both IP and hostname resolution. Since clients can browse by IP address, it indicates that the default gateway is correctly configured for IP traffic.
★ When this WOULD be the correct answer
In a different scenario where a client is unable to connect to any external resources, including both IP and hostname, the question might ask why the client cannot access the internet. In that case, if the default gateway is misconfigured, it would be the correct answer as it would block all traffic.
Why candidates choose this
Candidates may choose this option because they associate default gateway issues with connectivity problems, leading them to mistakenly believe it could affect hostname resolution despite existing IP connectivity.
✗The switch trunk native VLAN is wrong.Wrong answer — click to see why▾
Why this is wrong here
This option is wrong because the issue of clients being unable to browse by hostname is related to name resolution, not the configuration of the switch trunk native VLAN. The native VLAN configuration affects VLAN tagging and traffic flow, not DNS resolution.
★ When this WOULD be the correct answer
In a different scenario, if the question involved a network where clients are unable to communicate across VLANs due to misconfigured trunk settings, and the context indicated that hostname resolution relies on inter-VLAN routing, then this option could be correct.
Why candidates choose this
Candidates might choose this option due to a misunderstanding of how VLANs and trunking affect network communication, mistakenly believing that improper VLAN configurations could impact hostname resolution.
✗The server must run PPP before hostnames can work.Wrong answer — click to see why▾
Why this is wrong here
This option is incorrect because PPP (Point-to-Point Protocol) is not required for hostname resolution; it primarily deals with data link layer communication. Hostname resolution typically relies on DNS or local name resolution methods, not PPP.
★ When this WOULD be the correct answer
In a scenario where the question asks about the necessity of specific protocols for establishing network connections, such as a question about how to configure a network for dial-up connections, this option could be correct if it stated that PPP is required for establishing a connection before DNS queries can be made.
Why candidates choose this
Candidates might find this option tempting due to a misunderstanding of the relationship between network protocols and name resolution, leading them to incorrectly associate PPP with hostname functionality.
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
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Same concept, more angles
3 more ways this is tested on 200-301
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Clients on a network can browse the internet by IP address but fail when using hostnames. What is the most likely problem?
hard- A.The default gateway on the PC is incorrect.
- ✓ B.The client is using the wrong DNS server address.
- C.NAT overload is failing on the edge router.
- D.The switchport must be converted to a routed port.
Why B: The client can browse by IP address but not by hostname, which indicates that IP connectivity and routing are functional, but name resolution is failing. Since DNS translates hostnames to IP addresses, the most likely fault is that the client is configured with an incorrect DNS server address, preventing it from resolving domain names.
Variation 2. 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?
hard- ✓ A.The clients are missing a valid DNS server setting
- ✓ B.DNS queries may be blocked somewhere along the path
- C.The routers are missing NTP configuration
- D.The switch access ports should be changed to dynamic desirable
Why A: If IP connectivity works but hostnames fail, the problem is usually DNS configuration or DNS reachability, not general routing.
Variation 3. A host receives its IP address automatically but cannot resolve hostnames. Which additional service information is most likely missing from its configuration?
medium- ✓ A.A DNS server address
- B.A new MAC address
- C.A trunk native VLAN
- D.An OSPF router ID
Why A: 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.
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.