100-150 Practice Question: A small branch office has a Cisco Layer 2 access switch with three access ports assigned…
A small branch office has a Cisco Layer 2 access switch with three access ports assigned to VLAN 10 for the sales team and two access ports assigned to VLAN 20 for the finance team. The finance team reports that they cannot reach the sales team's shared file server, even though both teams are connected to the same physical switch. No router or Layer 3 switch is deployed at this branch. What is the most likely explanation for the connectivity failure?
⚠ Common exam trap
The trap here is assuming that two VLANs on the same physical switch can communicate directly because the hardware is shared.
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 10 and VLAN 20 are separate broadcast domains, and inter-VLAN traffic requires a Layer 3 device that is not present in this topology.
Because VLANs are independent broadcast domains, hosts in VLAN 10 and VLAN 20 cannot exchange traffic at Layer 2 even when they are attached to the same physical switch. Communication between VLANs requires a Layer 3 device to route packets between the subnets. With only a Layer 2 access switch in the branch, no such device exists, so the finance team cannot reach the sales server.
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 switch needs the ip routing global configuration command enabled so that it can forward frames between VLAN 10 and VLAN 20.
Why it's wrong here
The ip routing command enables Layer 3 routing functionality on a multilayer switch that supports it, but this branch switch is described as a Layer 2 access switch with no routing capability. Enabling that command on a Layer 2-only platform has no effect and would not create a path between VLANs. The real issue is the absence of any Layer 3 device, not a disabled feature on the access switch.
- ✓
VLAN 10 and VLAN 20 are separate broadcast domains, and inter-VLAN traffic requires a Layer 3 device that is not present in this topology.
Why this is correct
Each VLAN is its own broadcast domain, and hosts in different VLANs cannot communicate at Layer 2 because there is no shared broadcast segment. Forwarding between VLANs requires a Layer 3 device such as a router or multilayer switch performing inter-VLAN routing. Because the branch has only a Layer 2 access switch, no device exists to route traffic between VLAN 10 and VLAN 20, so the finance hosts cannot reach the sales server.
- ✗
The access ports must be configured as trunk ports so that frames from both VLANs can be carried between them.
Why it's wrong here
Trunk ports carry traffic for multiple VLANs between network devices such as switches, but they do not route traffic between VLANs. Configuring an access port as a trunk would not allow a host in VLAN 10 to reach a host in VLAN 20, because the frames still need a Layer 3 decision. The problem is the missing router or multilayer switch, not the port mode of the access ports.
- ✗
Spanning Tree Protocol has blocked the redundant path between the two VLANs, preventing traffic from flowing between them.
Why it's wrong here
Spanning Tree Protocol operates within a Layer 2 topology to prevent loops by blocking redundant links; it does not create or block paths between separate VLANs. VLAN 10 and VLAN 20 do not share a Layer 2 forwarding path at all, so STP state is irrelevant to their mutual reachability. The connectivity failure stems from the lack of Layer 3 routing, not from a blocked spanning-tree port.
Visual reference
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Written and reviewed by Johnson Ajibi, MSc IT Security
Security Systems Architect · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
This 100-150 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 100-150 exam.