220-1101 Networking Practice Question
A technician is troubleshooting a workstation that cannot connect to any network resources. The IP configuration shows an APIPA address (169.254.x.x). Other workstations on the same physical network are functioning normally. What is the MOST likely cause?
⚠ Common exam trap
CompTIA often tests the distinction between Layer 2 issues (like VLAN mismatch) and Layer 3 issues (like default gateway), and the trap here is that candidates assume an APIPA address always indicates a DHCP server problem, when in fact it can be caused by a switch port VLAN misconfiguration that isolates the client from the DHCP server.
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
✓
Switch port configured for a different VLAN
An APIPA address (169.254.x.x) is assigned when a DHCP client fails to receive a lease. Since other workstations on the same physical network are working, the issue is isolated to this workstation's switch port. If the switch port is configured for a different VLAN, the workstation's DHCP broadcast will not reach the DHCP server in the correct VLAN, causing the client to self-assign an APIPA address. This is the most likely cause because the physical connectivity is intact, but Layer 2 segmentation prevents DHCP communication.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Faulty network interface card
Why it's wrong here
A faulty NIC often results in a disconnected link or persistent link flapping, not an APIPA address. An APIPA address implies the link is up and the system attempted to get an IP via DHCP.
- ✓
Switch port configured for a different VLAN
Why this is correct
If the switch port is assigned to a VLAN that does not contain the DHCP server, the workstation cannot receive a valid IP address via DHCP. It then falls back to APIPA. This isolates the workstation from the rest of the network while keeping the link active.
- ✗
Duplicate IP address on the network
Why it's wrong here
A duplicate IP address produces an ARP conflict that typically triggers a Windows error pop-up and causes intermittent loss of connectivity, but the workstation would still hold a DHCP-assigned address rather than an APIPA link-local address. APIPA (169.254.x.x) only appears when DHCP discovery completely fails or times out, not when a duplicate address is detected. Thus a duplicate IP explains flapping or blocked traffic, not the automatic assignment of an APIPA address.
- ✗
Incorrect default gateway configured
Why it's wrong here
A misconfigured default gateway affects only routing beyond the local subnet; DHCP address acquisition occurs at Layer 2 and does not depend on the gateway setting. With an incorrect gateway, the client would still receive a valid IPv4 address from the DHCP server and would not fall back to APIPA. The presence of APIPA indicates the DHCP request never reached a server, which is a separate problem unrelated to the default gateway's value or reachability.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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