220-1101 Networking Practice Question
A technician configures a new workstation with DHCP. Initially, the workstation obtains an IP address of 192.168.1.100/24 with default gateway 192.168.1.1 and can browse the internet. After approximately 30 minutes, the user reports that internet access stops working, but the workstation can still ping other local devices on the same subnet. The technician runs ipconfig and sees that the workstation now has an IP address of 169.254.15.78. Which of the following is the MOST likely cause?
⚠ Common exam trap
Candidates often assume a DHCP scope exhaustion (Option A) is the cause, but the key clue is that the workstation initially had a valid IP and lost it after a period, which points to lease expiration and renewal failure, not a full scope.
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 lease expired and the workstation could not contact the DHCP server to renew it
The workstation initially received a valid DHCP lease (192.168.1.100/24). After 30 minutes, the lease expired, and the workstation failed to renew it from the DHCP server. As a result, Windows Automatic Private IP Addressing (APIPA) assigned a 169.254.x.x address, which allows local subnet communication but not internet access. This matches the symptom of losing internet while retaining local connectivity.
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 DHCP server has run out of available IP addresses in the scope
Why it's wrong here
A DHCP scope exhaustion means all addresses in the pool are already assigned to other clients, so the server cannot offer any IPv4 address during the initial DORA exchange. In that case the workstation would never have received a valid lease at time zero; it would fail immediately and self-assign an APIPA address. Because the machine did obtain a working address first and only lost connectivity later, the problem is a renewal failure, not a depleted scope.
- ✓
The DHCP lease expired and the workstation could not contact the DHCP server to renew it
Why this is correct
DHCP leases have a finite lifetime; the client begins attempting renewal at 50% of the lease (T1) and broadcast rebinding at 87.5% (T2). If the DHCP server is unreachable when the lease fully expires, the client is no longer permitted to use the assigned IP and falls back to an APIPA 169.254.x.x address. This scenario exactly matches a workstation that worked initially, then lost connectivity after roughly half a short lease interval on a typical SOHO router.
- ✗
The DNS server address provided by DHCP has become invalid
Why it's wrong here
An invalid DNS server address would not make the workstation change its IPv4 configuration to APIPA; DNS and DHCP address assignment are independent services at different network layers. The computer would keep its existing DHCP lease, default gateway, and IP address, but fail to resolve domain names correctly. An APIPA address, by contrast, is a self-assigned link-local IP used only when DHCP fails entirely, not when name resolution is degraded.
- ✗
The switch port the workstation is connected to was moved to a different VLAN without trunking
Why it's wrong here
Moving the switch port to a different VLAN without trunking would place the workstation in a different Layer 2 broadcast domain, so its DHCP DISCOVER messages—which rely on broadcast frames—would no longer reach the DHCP server. Such a change would typically cause immediate loss of connectivity and prevent the client from ever obtaining a valid address after the port reconfiguration; it would not cause the workstation to keep working normally and then experience a delayed renewal failure. The original valid IP assignment indicates the port and VLAN configuration were functioning correctly during initial setup.
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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.