For CompTIA A+ and CompTIA Network+
Practice where every answer shows its source
After each question, CertLighthouse shows why the right answer is right and why each wrong option is wrong, then links the standard or vendor documentation that proves it. Every question is written to the official exam objectives and checked by a human reviewer.
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Incorrect
N10-009 · TroubleshootingUsers on a new VLAN get 169.254.x.x addresses. The DHCP server is on another subnet and already has a scope for the VLAN. What is the MOST likely cause?
The DHCP scope for the new VLAN is exhausted.
Your answer
The router interface for the new VLAN has no DHCP relay configured.
Correct answer
Why your answer is wrong
A brand-new scope with no clients yet hasn't run out of addresses.
Why B is right
A client with no lease broadcasts DHCPDISCOVER on its own subnet. Routers don't forward broadcasts, so a server on another subnet only hears it through a relay agent. With no lease, the client falls back to a 169.254/16 link-local address.
Sources
RFC 2131, section 3.1
IETF · Clients broadcast DHCPDISCOVER locally; relay agents pass it to servers on other subnets.
Three exams, mapped objective by objective
The explanation is the product
A practice question teaches you something only when you find out why. CertLighthouse ends every scored question on the same screen: your pick, the correct answer, what was wrong with your choice, and a reason for each of the other options.
That reasoning is written for that question and approved with it. Nothing on the screen is generated while you wait, and explanations are never behind a paywall, including on free questions.
- Sources you can check
- Each answer links the RFC section, Microsoft Learn page, or registry entry behind it.
- Real simulations
- Configure a router, read command output, and match cables to ports with partial credit.
- Mock exams to the blueprint
- Up to 90 questions in 90 minutes, sampled to CompTIA's domain weights.
- Your own flashcard sets
- Save any question to a set and review it on a spaced schedule, offline.
Written in a clean room, checked by a person
Questions are written only from the published objectives and public primary sources. We never use exam dumps, recalled questions, or other prep vendors' material, and we never ask learners what they saw on an exam.
Before a question reaches you it passes automated checks on its evidence and its answer key, then review by an approved reviewer who holds or teaches the certification. When we change an answer key, the change and the reason go on a public corrections log.
For instructors and programs
CertLighthouse is built by an instructor who teaches CompTIA A+, and it's designed to work in a classroom: accessible simulations, class codes, and objective-level reporting are part of the plan for colleges and training programs.