220-1101 Networking Practice Question
A small office network uses an unmanaged switch to connect 20 workstations to a router. After connecting the 11th workstation, all previously connected workstations begin losing internet connectivity intermittently. The switch link lights remain solid green for all connected devices. The technician discovers that the new workstation has two active network interfaces, both plugged into the same switch. Which of the following is the MOST likely cause?
⚠ Common exam trap
Candidates often confuse a network loop with an IP address conflict, but the key clue is the dual active interfaces on the same switch, which creates a physical loop that affects all devices at Layer 2, not just the new workstation.
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
✓
Network loop
The new workstation has two active network interfaces both plugged into the same unmanaged switch, creating a physical network loop. This loop causes broadcast storms and MAC address table instability (the switch repeatedly learns the same MAC address on different ports), which overwhelms the switch and causes intermittent connectivity for all devices. Unmanaged switches lack Spanning Tree Protocol (STP) to detect and block redundant paths, so the loop is not automatically resolved.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
IP address conflict
Why it's wrong here
An IP address conflict affects only the specific device with the duplicate address, causing ARP table instability and intermittent connectivity for that host. The other workstations would continue to receive normal network service. Since the problem involves all 20 devices losing connectivity simultaneously, a single IP conflict cannot account for the widespread nature of the symptoms. The timing of the issue—immediately after adding the 11th workstation—is unrelated to a duplicate IP.
- ✗
Switch is faulty
Why it's wrong here
The unmanaged switch's link LEDs remain solid green on every port, confirming that Layer 1 physical connectivity is intact. A faulty switch typically exhibits persistent failures, such as dropped packets, unexpected reboots, or abnormal LED behavior, not intermittent loss that begins precisely when a new device is connected. The symptom is contingent on a topology change, which strongly suggests a logical loop rather than a hardware defect. A failing switch would not suddenly become intermittent only after a specific addition.
- ✓
Network loop
Why this is correct
Connecting a device with two active NICs to the same unmanaged switch creates a loop. This causes broadcast storms, overwhelming the network and causing intermittent connectivity for all devices. This matches the symptom of issues starting immediately after the 11th workstation was added.
- ✗
Exceeded DHCP scope
Why it's wrong here
Exceeding the DHCP scope would prevent the new workstation from obtaining a valid IP address, causing it to default to APIPA (169.254.x.x) and lack internet access. However, the ten existing workstations already have leased addresses and would continue working normally. The scenario describes all devices losing connectivity intermittently, which is not what a full scope does. A DHCP pool exhaustion is a unicast addressing issue, not a broadcast storm that affects the entire LAN.
Visual reference
Quick reference
Access Control Model Comparison
| Model | Acronym | Who Controls Access? | Best For |
|---|---|---|---|
| Discretionary Access Control | DAC | Resource owner | Small teams, file shares |
| Mandatory Access Control | MAC | System / security labels | Classified govt / military |
| Role-Based Access Control | RBAC | Administrator (via roles) | Enterprise environments |
| Attribute-Based Access Control | ABAC | Policy engine (user + resource attributes) | Fine-grained, dynamic policies |
| Rule-Based Access Control | RuBAC | System rules / ACLs | Firewall rules, network ACLs |
Go deeper
Related to this question
Learn chapter
Networking Hardware: Routers, Switches, APs
Key term
Media Access Control
Media Access Control (MAC) is a sublayer of the Data Link Layer in networking that controls how devices on the same network share access to the physical medium and uniquely identifies each device with a hardware address.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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