APIPA Address While Others Work: Diagnosing a Wrong VLAN Assignment
A user reports that their desktop computer cannot access any network shares. Other computers on the same switch can access the shares. The technician runs ipconfig /all on the affected computer and sees the following: IPv4 Address: 169.254.13.42, Subnet Mask: 255.255.0.0, Default Gateway: blank. Which of the following is the MOST likely cause?
Quick Answer
An address in the 169.254.x.x range is not something a DHCP server ever hands out; it is what Windows assigns itself through Automatic Private IP Addressing when it fails to receive any response from a DHCP server after several attempts. That single detail eliminates a huge range of possible causes, because it tells you this specific computer's DHCP request never reached the server, even though the explanation confirms other computers on the same physical switch have no trouble getting addresses and reaching shares. If the DHCP server itself were down or the switch had a hardware fault, every device would be affected, not just one. The most likely explanation for one device on a shared switch failing to reach an otherwise healthy DHCP server is that its port is isolated into a different broadcast domain than the one the DHCP server lives on, which is exactly what happens when a switch port is assigned to the wrong VLAN. DHCP requests are broadcasts, and broadcasts do not cross VLAN boundaries without a relay or router configured to forward them. Whenever you see one device self-assign an APIPA address while its neighbors on the same switch work fine, think about broadcast domain isolation, such as an incorrect VLAN assignment, rather than a DHCP server outage.
⚠ Common exam trap
The trap here is that candidates see a 169.254.x.x address and immediately assume the DHCP server is out of addresses or the adapter is faulty, but the key clue is that other computers on the same switch work, pointing to a layer-2 segmentation issue like VLAN misconfiguration rather than a DHCP server problem.
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 switch port the desktop is connected to is configured for the wrong VLAN.
The 169.254.x.x address is an Automatic Private IP Addressing (APIPA) address, assigned when a DHCP server is unreachable. Since other computers on the same switch can access network shares, the DHCP server is functional and has available addresses. The most likely cause is that the switch port is configured for the wrong VLAN, which isolates the desktop's broadcast domain, preventing it from reaching the DHCP server while other devices on the correct VLAN can communicate normally.
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 desktop's network adapter is faulty.
Why it's wrong here
A 169.254.x.x address is an APIPA self-assignment, meaning the DHCP server was unreachable, not that the NIC failed; a faulty adapter typically shows no link or no address at all. It is tempting because hardware faults do cause connectivity loss, but here the adapter clearly obtained a link-local address.
- ✗
The DHCP server has no available IP addresses in its scope.
Why it's wrong here
A scope exhausted of leases yields no offer, so the client self-assigns an APIPA address in 169.254.0.0/16 with no gateway, matching the output. It tempts because DHCP is clearly implicated, yet exhaustion is indistinguishable here from an unreachable or absent DHCP server.
- ✓
The switch port the desktop is connected to is configured for the wrong VLAN.
Why this is correct
An APIPA address of 169.254.x.x with no gateway means DHCP failed. If the switch port sits on a VLAN without a DHCP server, the desktop never obtains a lease, while other ports on correct VLANs succeed. This matches the isolated-failure symptom.
- ✗
The desktop's firewall is blocking DHCP traffic.
Why it's wrong here
A firewall blocking DHCP would prevent lease acquisition, producing the same APIPA address, but Windows Firewall permits DHCP by default and the symptom affects one host. It tempts as a plausible cause of failed DHCP, yet the stem gives no evidence of a locally configured block.
Visual reference
Go deeper
Related to this question
Learn chapter
Network Configuration: IP, DNS, DHCP
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.
Key term
Internet Protocol
Internet Protocol (IP) is the set of rules that governs how data is addressed, routed, and sent from one device to another across networks, including the internet.
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Same concept, more angles
2 more ways this is tested on 220-1101
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. A user reports that their desktop computer cannot access the internet, but it can access internal network resources and other computers on the local network. The technician runs ipconfig and sees the IP address is 169.254.15.22. Which of the following is the MOST likely cause of this issue?
easy- A.The DNS server is not responding
- ✓ B.The DHCP server is not responding
- C.The default gateway is misconfigured
- D.The network cable is unplugged
Why B: The IP address 169.254.15.22 is an Automatic Private IP Addressing (APIPA) address (169.254.0.0/16), which Windows assigns when a DHCP server is unreachable. Since the computer can still access local resources, the network stack is functional, but without a valid DHCP lease, it cannot obtain a routable IP, default gateway, or DNS server, thus losing internet access.
Variation 2. A technician is troubleshooting a workstation that cannot access any network resources. The technician runs ipconfig and sees that the IP address is 169.254.10.50 with subnet mask 255.255.0.0. The link lights on the NIC and the switch port are solid green. The technician connects the workstation to a different wall jack using a known-good cable, but the problem persists. Which of the following is the MOST likely cause?
easy- A.The switch port is administratively disabled
- ✓ B.The DHCP server is unavailable
- C.The default gateway is misconfigured on the router
- D.The DNS server is not responding
Why B: The IP address 169.254.10.50 with subnet mask 255.255.0.0 is an Automatic Private IP Addressing (APIPA) address, assigned by Windows when a DHCP server cannot be reached. Since the link lights are solid green and the cable and wall jack have been swapped with a known-good cable, the issue is not physical layer connectivity. The most likely cause is that the DHCP server is unavailable, preventing the workstation from obtaining a valid IP address.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 220-1101 practice question is part of Courseiva's free CompTIA 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 220-1101 exam.