CCNA Network Infrastructure and Connectivity Practice Question
Exhibit
C:\Users\Admin>ipconfig /all Windows IP Configuration Host Name . . . . . . . . . . . . : Host-A Primary Dns Suffix . . . . . . . : Node Type . . . . . . . . . . . . : Hybrid IP Routing Enabled. . . . . . . . : No WINS Proxy Enabled. . . . . . . . : No Ethernet adapter Ethernet0: Connection-specific DNS Suffix . : Description . . . . . . . . . . . : Intel(R) PRO/1000 MT Physical Address. . . . . . . . . : 00-50-56-8A-2B-1C DHCP Enabled. . . . . . . . . . . : Yes Autoconfiguration Enabled . . . . : Yes Link-local IPv6 Address . . . . . : fe80::250:56ff:fe8a:2b1c%12(Preferred) IPv4 Address. . . . . . . . . . . : 192.168.1.100(Preferred) Subnet Mask . . . . . . . . . . . : 255.255.255.0 Lease Obtained. . . . . . . . . . : Tuesday, October 5, 2023 10:00:00 AM Lease Expires . . . . . . . . . . : Wednesday, October 6, 2023 10:00:00 AM Default Gateway . . . . . . . . . : 192.168.1.1 DHCP Server . . . . . . . . . . . : 192.168.1.1 DNS Servers . . . . . . . . . . . : 8.8.8.8 Primary WINS Server . . . . . . . : NetBIOS over Tcpip. . . . . . . . : Enabled
A network engineer is troubleshooting an issue where a Windows 10 workstation (Host-A) cannot reach the internet, but can ping the local default gateway. The engineer runs 'ipconfig /all' on Host-A and reviews the output. What is the most likely cause of the problem?
⚠ Common exam trap
Candidates often assume a successful ping to the gateway means all Layer 3 connectivity is fine, overlooking that DNS is a separate service that can fail even when IP connectivity is intact.
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
✓
The DNS server is configured as a public DNS server that may be unreachable due to network policy or firewall.
Host-A can ping the default gateway, which confirms that Layer 3 connectivity to the local network is working and that the subnet mask and default gateway are correctly configured. The inability to reach the internet despite this connectivity points to a name resolution failure, likely caused by an incorrect or unreachable DNS server. A public DNS server (e.g., 8.8.8.8) may be blocked by corporate firewall policy, preventing Host-A from resolving internet domain names.
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 subnet mask is incorrect.
Why it's wrong here
The subnet mask 255.255.255.0 defines a /24 network and is entirely consistent with the host address 192.168.1.100. This mask yields a network address of 192.168.1.0 with 254 usable host addresses, and 192.168.1.100 falls cleanly within that range. There is no subnetting error, CIDR mismatch, or boundary violation that would make this mask incorrect.
- ✗
The default gateway is missing or incorrect.
Why it's wrong here
The default gateway is listed as 192.168.1.1, which lies on the same /24 subnet as the host's 192.168.1.100 address. A default gateway must be reachable at Layer 2 for off-subnet traffic to be forwarded; since 192.168.1.1 is in the host's directly connected subnet, that condition is satisfied. The gateway is neither missing nor misconfigured to an unreachable or off-subnet address.
- ✓
The DNS server is configured as a public DNS server that may be unreachable due to network policy or firewall.
Why this is correct
The DNS server is 8.8.8.8, which is a public Google DNS server outside the local network domain. In many enterprise or restrictive network environments, outbound UDP/TCP port 53 to public DNS servers is blocked by firewall policy or requires an internal DNS forwarder. Without reachable DNS, the host cannot resolve domain names, causing connectivity failures even though IP addressing, subnet mask, and default gateway are all correct; this makes DNS misconfiguration the most plausible cause.
- ✗
The host has obtained an APIPA address (169.254.x.x).
Why it's wrong here
APIPA addresses are self-assigned in the 169.254.0.0/16 range when a DHCP server is unavailable. Here the host has a 192.168.1.100 address, which is a private, valid, DHCP-allocatable IPv4 address and is not in the APIPA range. Therefore the host did not fail DHCP and is not in link-local fallback mode.
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.
✓The DNS server is configured as a public DNS server that may be unreachable due to network policy or firewall.Correct answer▾
Why this is correct
The DNS server is 8.8.8.8, which is a public Google DNS server outside the local network domain. In many enterprise or restrictive network environments, outbound UDP/TCP port 53 to public DNS servers is blocked by firewall policy or requires an internal DNS forwarder. Without reachable DNS, the host cannot resolve domain names, causing connectivity failures even though IP addressing, subnet mask, and default gateway are all correct; this makes DNS misconfiguration the most plausible cause.
✗The subnet mask is incorrect.Wrong answer — click to see why▾
Why this is wrong here
The subnet mask 255.255.255.0 is correct for a /24 network, so it is not the cause of the problem.
Why candidates choose this
Students often suspect subnet mask issues when connectivity fails, but here the mask is correct and the host can ping the gateway, indicating local connectivity works.
✗The default gateway is missing or incorrect.Wrong answer — click to see why▾
Why this is wrong here
The default gateway is correctly set to 192.168.1.1, and the host can ping it, so the gateway is not missing or incorrect.
Why candidates choose this
A missing or incorrect default gateway is a common cause of internet connectivity loss, but since the host can ping the gateway, this is not the issue.
✗The host has obtained an APIPA address (169.254.x.x).Wrong answer — click to see why▾
Why this is wrong here
The IPv4 address is 192.168.1.100, which is a valid private address, not an APIPA address (169.254.x.x). APIPA addresses are used when DHCP fails, but here the host has a proper address.
Why candidates choose this
APIPA addresses are a common cause of connectivity issues when DHCP fails, but the host's IP address is not in the APIPA range, so this is not the problem.
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
IPv4 Address Class Summary
| Class | First Octet Range | Default Mask | Networks | Hosts per Network |
|---|---|---|---|---|
| A | 1–126 | /8 (255.0.0.0) | 126 | 16,777,214 |
| B | 128–191 | /16 (255.255.0.0) | 16,384 | 65,534 |
| C | 192–223 | /24 (255.255.255.0) | 2,097,152 | 254 |
| D | 224–239 | N/A | Multicast groups | — |
| E | 240–255 | N/A | Reserved / experimental | — |
127.x.x.x is reserved for loopback. Modern networks use CIDR (classless) rather than classful addressing.
Go deeper
Related to this question
Learn chapter
DNS Resolution Process
Key term
DNS
DNS is the system that translates human-friendly domain names like example.com into machine-readable IP addresses so computers can find each other on a network.
Key term
ICMP
ICMP is a network-layer protocol used by network devices to send error messages and operational information about network connectivity.
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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.