CCNA Network Infrastructure and Connectivity Practice Question
A network administrator is configuring a new Windows 10 workstation on a network that uses DHCP. The workstation receives an IPv4 address of 169.254.10.20 with a subnet mask of 255.255.0.0 and no default gateway. The user cannot access the internet or other subnets. What is the most likely cause of this issue?
⚠ Common exam trap
Cisco often tests the misconception that a 169.254.x.x address indicates a duplicate IP or a subnet mask issue, but the real trap is that APIPA is a direct symptom of DHCP server unavailability, not a configuration error on the client.
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 DHCP server is unreachable or not responding.
The IP address 169.254.10.20 with a /16 subnet mask is an Automatic Private IP Addressing (APIPA) address, which Windows assigns when a DHCP discovery broadcast (DHCPDISCOVER) fails to receive a response from a DHCP server. Without a valid DHCP lease, the workstation has no default gateway, so it cannot communicate outside its local subnet, explaining the lack of internet or inter-subnet access. The most likely cause is that the DHCP server is unreachable or not responding, forcing the client to self-assign an APIPA address.
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 workstation has a duplicate IP address conflict.
Why it's wrong here
An IP address conflict occurs when two hosts use the same IP in the same subnet; the OS detects it via ARP and typically disables the interface or shows a balloon warning, but the address remains in the configured range. It does not trigger an APIPA self-assignment; the host would still have a gateway and a valid, albeit conflicting, address. The observed 169.254.x.x address with no default gateway is the hallmark of a DHCP failure, not a duplicate-IP condition.
- ✗
The workstation's DNS server configuration is incorrect.
Why it's wrong here
Incorrect DNS server settings break hostname resolution only; the interface still obtains its IP address, subnet mask, and default gateway through DHCP. The scenario shows a workstation with an APIPA address (169.254.0.0/16), which the OS assigns when no DHCP response is received, and the absence of a default gateway indicates the DHCP lease never succeeded. A DNS misconfiguration would leave a valid, routable IP and a gateway, so it cannot explain the given symptoms.
- ✗
The workstation's subnet mask is misconfigured.
Why it's wrong here
The subnet mask 255.255.0.0 is the standard mask for the 169.254.0.0/16 APIPA range; it is automatically configured by the OS as part of the link-local addressing process, not a user misconfiguration. If the subnet mask were misconfigured manually, the IP address would still be from a different range (e.g., a private or public range), and the workstation might still have a default gateway. Here the address itself is the APIPA block, so the root cause is the failure to contact a DHCP server, not a mask error.
- ✓
The DHCP server is unreachable or not responding.
Why this is correct
When a DHCP client fails to receive an IP address from a DHCP server, it self-assigns an APIPA address from the 169.254.0.0/16 range. This explains the observed address and the absence of a default gateway.
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 DHCP server is unreachable or not responding.Correct answer▾
Why this is correct
When a DHCP client fails to receive an IP address from a DHCP server, it self-assigns an APIPA address from the 169.254.0.0/16 range. This explains the observed address and the absence of a default gateway.
✗The workstation has a duplicate IP address conflict.Wrong answer — click to see why▾
Why this is wrong here
Duplicate IP conflicts typically result in a warning but do not cause the system to assign a 169.254.x.x address.
✗The workstation's DNS server configuration is incorrect.Wrong answer — click to see why▾
Why this is wrong here
DNS issues do not affect IP address assignment via DHCP.
✗The workstation's subnet mask is misconfigured.Wrong answer — click to see why▾
Why this is wrong here
The subnet mask is correct for the APIPA range; the problem is the lack of a DHCP server response.
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
IPv4 Addressing and Address Classes
Key term
DHCP server
A DHCP server is a network device or service that automatically assigns IP addresses and other network configuration parameters to devices on a network, eliminating the need for manual configuration.
Key term
Automatic Private Internet Protocol Addressing
A fallback method used by a device to automatically assign itself an IP address when it cannot obtain one from a DHCP server.
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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.