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200-901 Practice Question: Which TWO of the following are common causes of…
Which TWO of the following are common causes of VLAN connectivity issues?
⚠ Common exam trap
Cisco often tests the distinction between Layer 2 and Layer 3 issues, so candidates mistakenly select subnet mask or default gateway problems as VLAN connectivity issues when those are actually routing or host configuration problems.
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
✓
VLAN not created on all switches
VLANs must exist in the VLAN database of every switch that needs to forward traffic for that VLAN. If a VLAN is not created on a switch, interfaces assigned to that VLAN will be in an inactive or error-disabled state, and the switch will not forward frames for that VLAN across trunk links. This is a common misconfiguration when adding a new VLAN to a network without propagating it to all switches.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
VLAN not created on all switches
Why this is correct
If a VLAN is missing on a switch, ports assigned to that VLAN will be down.
- ✗
Mismatched subnet masks on access ports
Why it's wrong here
This is a Layer 3 issue, not a VLAN issue.
- ✗
Incorrect default gateway
Why it's wrong here
Default gateway is used for routing between subnets, not for VLAN connectivity.
- ✓
Mismatched VLAN IDs on trunk ports
Why this is correct
If trunk ports have different allowed VLANs or native VLAN mismatch, traffic may be dropped.
- ✗
STP blocking port
Why it's wrong here
STP blocking is a loop prevention mechanism and is not specifically a VLAN issue.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-901 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 200-901 exam.